I had the exact same problem, and it turned out to be the fuel lines. The inner walls of the lines were deteriorating, and they were only 4-5 years old. Replacing the fuel lines solved the issue. I think it was because I had been using regular unleaded instead of non-ethanol fuel with my 4-stroke Merc engine.
Replace ALL of your fuel lines, fuel filter (again) and never ever use regular gas in there. Only non-ethanol fuel, always. The alcohol in regular gas is deteriorating the rubber components in the fuel system.
Just a little friendly advice, when you were trying to take the filter off, you had the tool up on the threads. As you are squeezing, you are putting pressure on the threads, squeezing it tighter. Lower the tool more towards the middle of the filter! Just a little helpful tip!
Jengeling connections is definitely the right move. This feels like a puzzle and I know you are the one who can solve it. The feeling once you solve it is the best feeling, so keep on!
Definitely think its the fuel lines giving you that problem ! Huge respect for always staying positive and managing to make a plan when needed 🙏🏻 bahamas will be seeing you shortly !
Dude. Hang in there bro. It’s a labor of love. Not a lot of people get to live like us. We live where people vacation. Never forget that part. You’ll get it back up and going and you’ll be smarter when you figure it out.
The little square block that the main fuel line goes to is the pump that fills the VST. That diaphragm is probably shot... super stiff. To prove this out, take someone out with you and have them pump the printer bulb and continue to pump the bulb while trying to accelerate out of the hole. If the engine runs good and gets the boat on plane then you know that pump is today and not filling the vst tank. That's where I would start.
You will get there soon , your learning more and more about how boats work and that will be a big advantage in the future. Plus makes you content . I have faith in you xx
Judging by the standards the last technician has left those motors in for you, I would go ahead and replace all fuel lines and filters, as well as test all related electrical connections and check all grounds. Great job, love your videos!
I have a similar size boat and launch solo a lot. Consider grabbing some trailer guide posts. Throwing it back on the trailer will be aligned and a lot easier.
Pump is probably going bad. Another commenter mentioned fuel lines collapsing internally, and that is a very good possibility too. My bet is either pump going out or contaminated fuel. Run new fuel from a separate source and change your fuel/water separator. I had the same problem over the summer with mine. Was the replacement Chinese pump. Total junk.
Hey bud the issue is the Lil rubber hose between the high pressure fuel pump and the high pressure output hose pull the vst back apart and pull the high pressure fuel pump out you will find you're issue
There’s no shame in taking it to a professional, your efforts have surpassed anything I’d have imagined - you’ll need confidence in the motors if you’re going to go to the Bahamas. Keep the faith but also don’t let the heart cloud your judgment 🙂👍👏
I know exactly how you feel when fixing stuff and it doesn't work. Sooooo irritating! Just a matter of keep going -_- Nice video though, keep it going!
Stabbing a wide metal bar(2' flat tire lever) through and out the other side of a stuck flter works more so than a small thin screw driver will just open it like a can opener. But a wide bar through both sides has always worked for me
I had a similar issue with my 2 stoke merc. After chasing my tail and rebuilding the VST. It was a dry-rotted fuel line from the tank to the fuel filter, which was allowing air into the fuel system, causing the RPM to fluxuate under load. My advice is to start with simple stuff, fuel lines, filters, fittings, filter housing, etc... I replaced the fuel pump inside the VST, the vacuum fuel pump, rebuilt the VST, fuel filter housing, and new fuel filter. At the end all it was; was an old fuel line allowing air into the fuel system.
Pro tip Capt, once you fire up your engines leave the lines tied to dock and do both engines separate forward and reverse idle to see if controls work. And try steerage. Keep hydraulic fluid and kit incase you lose steerage underway or at the dock. There is also a RUclips channel that shows how to solo splash you boat. Hollywood is a great marina. I used to live on my sailboat there.
Check the fuel pressure coming out of the pump at the pump. Replace all fuel lines. I'm suspecting a fuel pump issue. Do not give up. You don't seem like that type of guy. Those kinds of problems that I have delt with and conquered over the years have given great satisfaction to me. Never give up.
Check make sure you don’t have water in your fuel. it happened to me before same engine, replace the fuel filter from the tank. And used a water fuel treatment for the fuel.
Brandon, definitely fuel issue, that fuel pump seems like new, the outside fuelpump has rust on its bracket, the oem one doesn't rust like that. IT SEEMS, that that motor had that problem long time ago. I suggest to change the fuel lines, and both fuel pumps, but for now just the fuel lines and prime bulb. watch out for the cheap prime bulb kits, the fuel lines deteriorates inside and clog your fuel floater
Brandon awesome content . the boat that keeps on giveing LOL . as i am boat owner as well and btw iam from Austalia . very very interesting content and videoing by yourself LOL ..anyways looking forward to the next video .. BIG THUMBS UP 👍😃👍
Brandon, Get with Gus, from YT channel, “In Too Deep”. I think he’s in Fl atm. He’s an amazing young guy man and a genius with any motor - especially marine motors. He’s a lovely dude and very knowledgeable.
He has seen his channel before… I have been dealing with an engine issue and I just found the other day that it was the electrical connector… looks like it’s perfectly fine and connecting but the connection isn’t good inside it
You need work bench and vice nice getting it off you are quite the mechanic even if you try more than once I have that problem sorry for all you have put into this thank goodness you made it home later
I had a similar issue on my Yamaha. Ended up being a piece of debris from the fuel tank got sucked into the fuel pick up line and every time I throttled up it sucked further up then when I lost power it floated back down. Back and forth it would go. Replaced the pickup and anti siphon valve. Good to go now.
I had an older Optimax you may need to clean out the air injectors and fuel injectors. Also see if its running on all 6 cylinders . Check the plugs see if its firing on all 6. I been threw this. One step at a time. Don't get frustrated you will trace out the issue.
I have an Optimax on my Whaler. Had one in an older boat. Check fuel lines. I had a line that was "2 ply" with an inner layer and outer layer. Those layers separated with age and the vacuum pressure would collapse the inner layer, sort of pinch it closed, and cut the fuel supply. Real similar issue, the harder I throttled the more that vacuum increased, and it cut off.
Is hard to accept but best way to enjoy the beautiful FL weather is by having time. Work on selling those and getting four strokes even used ones. Check for electrical issues also.
I totally understand the frustration man. And everyone says “buy outboards” I think everything breaks on a boat eventually regardless. I watch your videos and when you bought this boat wasn’t the port motor the one you couldn’t test? Maybe there is something he didn’t tell you.
try and run motor on a separate small 5 gallon portable fuel tank. this will eliminate any fuel issue like water in the fuel I would start there hope this may help you. that's what I have done in the past on my boat.
Optimax need a lot of power to run. I think in a previous video you put in some fancy batteries. Regular 1000 cca batteries are what you need. You can buy new walbro fuel pumps. Just get the p/n off the pump. Fraction of the cost of a Mercury walbro fuel pump. If you have a stuck pump you can run backwards and break them free. Then run them in a bucket of fuel cleaner for hour.
I work on optimax motors all the time. You need to invest in the gauges for the air and fuel so you can see in real time what is going on. There should be a 10psi difference between the air and fuel side.
I had 150 optimaxs on like 4 boats ago. I remember I had an issue like yours on one and it was an intermittent problem with the alternator. Replaced alternator and it was fixed. It was hard for mechanic to diagnose cause it was intermittent so I had to really figure it out myself.
After owning an optimax motor, I will *never* own another one. A mercury dealership mechanic once said to me "The Optimax is like Mercury said to it's engineers 'Put every single invention you've ever contemplated into a single fuel system and hope it all works together.'"
It's the fuel pump inside the VST. Yoi mentioned it lookedvifvitvhad been apart before. I'll bet you it was and whoever replaced the pump with a cheap Amazon pump ($36). You'll have to spend more for the oem.
Brandon, I had a merc 150 that randomly just cut out. Sometimes it would run for 8 hours straight, other times it would cut after 3 mins of running. Sometimes it would fire back up, othertimes it would be dead for hours. Turns out the ECU drives the fuel pump circuit. My ecu had corrosion inside the board and the fuel pump circuit was damage, causing intermittent random cut out of the electronic fuel pump. The give away was no fuel pressure at the rail when the engine died. It also didn't cycle the fuel pump when switching the ignition on. You can hear it prime the system when your switch the key on. If that stops, it's the ecu failing to drive your fuel pump. Carry a length of wire, direct from the positive terminal to the fuel pump terminal, and manually drive the fuel pump next time it dies. If it immediately fires and runs, that's your problem. A relay off the ignition direct to the fuel pump works a treat. Hopefully this helps you diagnose a potential ecu issue driving your fuel pump.
Consider buying the guide poles for the trailer. Also, even without the guide poles, if the bunks are spaced out correctly, the boat should self right itself. Make sure the bunks are on the strakes. Also, for those saying fuel line is your issue, if they are black USCG approved, they would not have a lining. The grey do have linings the ethanol deteriorates.
If you induced this problem go back to the fuel pump you may have cover the pulse hole with a price of the gasket or debris or you may have installed it incorrectly
![BLACK BAG - Official Trailer [HD] - Only in Theaters March 14](http://i.ytimg.com/vi/Du0Xp8WX_7I/mqdefault.jpg)
I think I know what’s wrong. You keep bringing bananas on your boat. That’s definitely the root cause of all your issues
I had the exact same problem, and it turned out to be the fuel lines. The inner walls of the lines were deteriorating, and they were only 4-5 years old. Replacing the fuel lines solved the issue. I think it was because I had been using regular unleaded instead of non-ethanol fuel with my 4-stroke Merc engine.
fuel lines are my bet too
These type of videos are great for everyone as a lot of content creators only show the good bits and not the hardship owners go through. Nice One 👍
Replace ALL of your fuel lines, fuel filter (again) and never ever use regular gas in there. Only non-ethanol fuel, always. The alcohol in regular gas is deteriorating the rubber components in the fuel system.
yep had the same problem last year new lines and filters and it was good as new
Just a little friendly advice, when you were trying to take the filter off, you had the tool up on the threads. As you are squeezing, you are putting pressure on the threads, squeezing it tighter. Lower the tool more towards the middle of the filter! Just a little helpful tip!
Keep your head up Brandon. You are becoming a good boat motor mechanic. Thanks for the video. Keep on keeping on.
Respect to you for the way you deal with life’s challenges. 👊
Jengeling connections is definitely the right move. This feels like a puzzle and I know you are the one who can solve it. The feeling once you solve it is the best feeling, so keep on!
your killing it and learning a lot in the process
Definitely think its the fuel lines giving you that problem ! Huge respect for always staying positive and managing to make a plan when needed 🙏🏻 bahamas will be seeing you shortly !
I just love your positive attitude. Keep the videos coming
It’s hard to do things yourself but better in the end so keep up the good work
Dude. Hang in there bro. It’s a labor of love. Not a lot of people get to live like us. We live where people vacation. Never forget that part. You’ll get it back up and going and you’ll be smarter when you figure it out.
The little square block that the main fuel line goes to is the pump that fills the VST. That diaphragm is probably shot... super stiff. To prove this out, take someone out with you and have them pump the printer bulb and continue to pump the bulb while trying to accelerate out of the hole. If the engine runs good and gets the boat on plane then you know that pump is today and not filling the vst tank. That's where I would start.
Some boating days are like that. Keep the dream alive and your head up.
You will get there soon , your learning more and more about how boats work and that will be a big advantage in the future. Plus makes you content . I have faith in you xx
I like how youre just taking care of business right on the sidewalk. very relatable. my only option most of the time
Sorry to hear all the issues you keep having with your boat, see prayers your way that you figure out whats going on and can get it fixed.
The issue is your fuel lines. Replace them. 100% I had the same issue with one of my pathfinders
Love your channel. Keep at it with the boat. Do not try to make the run to the Bahamas. Certainly not ready for that. Good luck. 🍻
you seriously are so patient. you got this.
If you are truly going to go to the Bahamas, I would spend the money and bring it to a Merc dealer and have them go through the fuel system.
A dealer would charge an arm and leg. Better find a good mechanic that knows Merc engine.
Dealers won't touch an optimax in 2025
Judging by the standards the last technician has left those motors in for you, I would go ahead and replace all fuel lines and filters, as well as test all related electrical connections and check all grounds. Great job, love your videos!
Poor Mr.B☹️😮that darn boat has given you more grief than pleasure😵💫Well I hope you do get to fix 🤘👍 love from melbourne ❤️❤️❤️❤️
Trooper! Worth it for those days on the water.
love the videos and your never quit/I can fix it attitude... but noway I would take that boat more than a mile offshore. Taking it to the Bahamas....
I have a similar size boat and launch solo a lot. Consider grabbing some trailer guide posts. Throwing it back on the trailer will be aligned and a lot easier.
Always feel them fuel filters up befor putting back on helps a lot
Welcome to Florida and the mosquitos 😀We had them really bad in south Texas also
Pump is probably going bad. Another commenter mentioned fuel lines collapsing internally, and that is a very good possibility too. My bet is either pump going out or contaminated fuel. Run new fuel from a separate source and change your fuel/water separator. I had the same problem over the summer with mine. Was the replacement Chinese pump. Total junk.
Hey bud the issue is the Lil rubber hose between the high pressure fuel pump and the high pressure output hose pull the vst back apart and pull the high pressure fuel pump out you will find you're issue
There’s no shame in taking it to a professional, your efforts have surpassed anything I’d have imagined - you’ll need confidence in the motors if you’re going to go to the Bahamas. Keep the faith but also don’t let the heart cloud your judgment 🙂👍👏
Get the guide poles for the trailer. The boat will always be perfectly center when pulling it out of the water.
I feel you need Gus from In To Deep. He should be in Florida by know. He can teach you so much. Don’t stress things will work out.
I know exactly how you feel when fixing stuff and it doesn't work. Sooooo irritating! Just a matter of keep going -_- Nice video though, keep it going!
I would replace fuel lines. Just remember that at least you are trying and doing this yourself. Don’t get yourself down. Keep trying
Stabbing a wide metal bar(2' flat tire lever) through and out the other side of a stuck flter works more so than a small thin screw driver will just open it like a can opener. But a wide bar through both sides has always worked for me
love the videos and the boat is so nice keep up the hard work brandon
Almost got all the kinks out bro. Keep working on it and you will have a solid machine.
I had a similar issue with my 2 stoke merc. After chasing my tail and rebuilding the VST. It was a dry-rotted fuel line from the tank to the fuel filter, which was allowing air into the fuel system, causing the RPM to fluxuate under load. My advice is to start with simple stuff, fuel lines, filters, fittings, filter housing, etc... I replaced the fuel pump inside the VST, the vacuum fuel pump, rebuilt the VST, fuel filter housing, and new fuel filter. At the end all it was; was an old fuel line allowing air into the fuel system.
Pro tip Capt, once you fire up your engines leave the lines tied to dock and do both engines separate forward and reverse idle to see if controls work. And try steerage. Keep hydraulic fluid and kit incase you lose steerage underway or at the dock. There is also a RUclips channel that shows how to solo splash you boat. Hollywood is a great marina. I used to live on my sailboat there.
Ohh that’s not good news!!😢
I hope that you’re able to fix the issue and carry on having a great time in Florida!🥰♥️
Check the fuel pressure coming out of the pump at the pump. Replace all fuel lines. I'm suspecting a fuel pump issue. Do not give up. You don't seem like that type of guy. Those kinds of problems that I have delt with and conquered over the years have given great satisfaction to me. Never give up.
You have a fuel problem for sure. Recheck those floats and make sure it's not hanging up inside the bowl.
Check make sure you don’t have water in your fuel. it happened to me before same engine, replace the fuel filter from the tank. And used a water fuel treatment for the fuel.
Brandon, definitely fuel issue, that fuel pump seems like new, the outside fuelpump has rust on its bracket, the oem one doesn't rust like that. IT SEEMS, that that motor had that problem long time ago. I suggest to change the fuel lines, and both fuel pumps, but for now just the fuel lines and prime bulb. watch out for the cheap prime bulb kits, the fuel lines deteriorates inside and clog your fuel floater
I had exactly the same issue, changed both low pressure fuel pumps and she's all good
Keep your head up you will figure it out
Brandon awesome content . the boat that keeps on giveing LOL . as i am boat owner as well and btw iam from Austalia . very very interesting content and videoing by yourself LOL ..anyways looking forward to the next video .. BIG THUMBS UP 👍😃👍
Brandon,
Get with Gus, from YT channel, “In Too Deep”. I think he’s in Fl atm. He’s an amazing young guy man and a genius with any motor - especially marine motors.
He’s a lovely dude and very knowledgeable.
He has seen his channel before… I have been dealing with an engine issue and I just found the other day that it was the electrical connector… looks like it’s perfectly fine and connecting but the connection isn’t good inside it
Blame it on that guy that hit your boat. Sue the hell outta him and get a brand new boat out of the deal. LOL :)
Change the fuel ball u pump up. Could have a pin size hole or in the fuel line. Getting air in the fuel line.
You need work bench and vice nice getting it off you are quite the mechanic even if you try more than once I have that problem sorry for all you have put into this thank goodness you made it home later
Bruh. Well, as usually, everything will be good in the end. And if its not good, its not the end yet…. wish you all the best!
I had a similar issue on my Yamaha. Ended up being a piece of debris from the fuel tank got sucked into the fuel pick up line and every time I throttled up it sucked further up then when I lost power it floated back down. Back and forth it would go. Replaced the pickup and anti siphon valve. Good to go now.
you get a filter tool with a strap on it, or lether strap, that one is good. as it wont smash the filter if you have to use force.
Make sure to use red lock tight on the threads of your new filter!
Ellie could get that filter off no problem!😂
😆😆
Fuel lines!!
I had an older Optimax you may need to clean out the air injectors and fuel injectors. Also see if its running on all 6 cylinders . Check the plugs see if its firing on all 6. I been threw this. One step at a time. Don't get frustrated you will trace out the issue.
I have an Optimax on my Whaler. Had one in an older boat. Check fuel lines. I had a line that was "2 ply" with an inner layer and outer layer. Those layers separated with age and the vacuum pressure would collapse the inner layer, sort of pinch it closed, and cut the fuel supply. Real similar issue, the harder I throttled the more that vacuum increased, and it cut off.
Check your fuel line and manual pump. Only go with OEM.
Is hard to accept but best way to enjoy the beautiful FL weather is by having time. Work on selling those and getting four strokes even used ones.
Check for electrical issues also.
If you are planning on going to the Bahamas you might want to put a steering cylinder on each engine
I totally understand the frustration man. And everyone says “buy outboards” I think everything breaks on a boat eventually regardless. I watch your videos and when you bought this boat wasn’t the port motor the one you couldn’t test? Maybe there is something he didn’t tell you.
try and run motor on a separate small 5 gallon portable fuel tank. this will eliminate any fuel issue like water in the fuel I would start there hope this may help you. that's what I have done in the past on my boat.
Hope you diagnose the issues and get back on the water.
Thank God you have twin screws! Single prop boating is a gamble with a sizable craft you can’t paddle when SHTF!
Optimax need a lot of power to run. I think in a previous video you put in some fancy batteries. Regular 1000 cca batteries are what you need. You can buy new walbro fuel pumps. Just get the p/n off the pump. Fraction of the cost of a Mercury walbro fuel pump. If you have a stuck pump you can run backwards and break them free. Then run them in a bucket of fuel cleaner for hour.
Had the same issue with my motor, so i bought a new one hasn't missed a beat for 6 years
I love all of your videos!
I work on optimax motors all the time. You need to invest in the gauges for the air and fuel so you can see in real time what is going on. There should be a 10psi difference between the air and fuel side.
More than likely the high pressure fuel pump.
I had 150 optimaxs on like 4 boats ago. I remember I had an issue like yours on one and it was an intermittent problem with the alternator. Replaced alternator and it was fixed. It was hard for mechanic to diagnose cause it was intermittent so I had to really figure it out myself.
hopefully it gets better
After owning an optimax motor, I will *never* own another one. A mercury dealership mechanic once said to me "The Optimax is like Mercury said to it's engineers 'Put every single invention you've ever contemplated into a single fuel system and hope it all works together.'"
It’s just amazes me when they make something or you have to take more stuff off just to get the one thing you’re trying to fix😅
That float is sticking I’d bet. You pointed it out when you took the vst apart.
It's the fuel pump inside the VST. Yoi mentioned it lookedvifvitvhad been apart before. I'll bet you it was and whoever replaced the pump with a cheap Amazon pump ($36). You'll have to spend more for the oem.
When I’m sick nd beyond my ability to get better on my own, I go to a dr/professional
Check primer bulb see if it collapsed take gas cap off see you pulling vacuum
Soon enough, with all of this experience, you can open your own boat repair shop 🛠
The nickname for those motors is Optiboom.
Brandon, I had a merc 150 that randomly just cut out. Sometimes it would run for 8 hours straight, other times it would cut after 3 mins of running. Sometimes it would fire back up, othertimes it would be dead for hours.
Turns out the ECU drives the fuel pump circuit. My ecu had corrosion inside the board and the fuel pump circuit was damage, causing intermittent random cut out of the electronic fuel pump.
The give away was no fuel pressure at the rail when the engine died. It also didn't cycle the fuel pump when switching the ignition on. You can hear it prime the system when your switch the key on. If that stops, it's the ecu failing to drive your fuel pump.
Carry a length of wire, direct from the positive terminal to the fuel pump terminal, and manually drive the fuel pump next time it dies. If it immediately fires and runs, that's your problem. A relay off the ignition direct to the fuel pump works a treat.
Hopefully this helps you diagnose a potential ecu issue driving your fuel pump.
Check your flywheel, sometimes magnets will break off and create similar issue
Consider buying the guide poles for the trailer. Also, even without the guide poles, if the bunks are spaced out correctly, the boat should self right itself. Make sure the bunks are on the strakes.
Also, for those saying fuel line is your issue, if they are black USCG approved, they would not have a lining. The grey do have linings the ethanol deteriorates.
sone one must of really ova tightened that oil filter when the put it on.
That thing you called a check valve with the diaphragm looked like a mechanical fuel pump. Try rebuilding it.
Check the float. It connects to a needle and seat. Something is hanging up and not letting fuel in. You probably have a needle getting stuck.
If you induced this problem go back to the fuel pump you may have cover the pulse hole with a price of the gasket or debris or you may have installed it incorrectly
Have you checked the flux capacitor? Remember that the angle of the dangle is equivalent to the heat of the meat. That should do it.
It's definitely time to get some newish engines.
Good luck Sr with old and used boat. You are going to have two days happy . When you buy it and when you sale then.
Get yourself a mechanics toolkit to keep on your boat or in your truck.
I have the same issue , in my case the high fuel pump , it's idle but when put it under power the pump don't deliver the required fuel.
good job mate
Think you got your port and starboard confused my dude. Your helm is on the starboard side.
Might be time to have a shop look at it
20:21 you have to go through all that just give me a call I'll be there 😂
Don’t use the oil filter wrench over the threads, I reckon
Change your fuel pump diaphragm’s and a previous video you said they we’re running cold change the poppet valves