Great video! Just wanted to comment on an observation. Your engine is running extremely lean. That hesitation, or sneeze, you hear at idle is a lean sneeze. This is usually due to a dirty carb. Running like that for a while can cause you lose a cylinder because if its running lean on fuel, its also running lean on oil. Just something to look into. Keep up the good work!
Edited/revised. Glad to see the water diverters were checked. If you were doing one head, you should do both. Deleting the thermostats does not solve your overheat problem, it just multiplies the complications with the motor. Definite strong possibility of cold seizing engine damage due to pistons getting warmer faster than engine block/cylinder and locking up motor. Thermostats regulate temperature to prevent this. Motor will run rough in more situations and will not idle as well. Possibly will overheat engine in certain situations during idle as there is no backpressure to keep the water around the block and cylinder walls to evenly distribute the cooling water.
OK, a few things to think about here. First, both of those thermostats were blown open, NG. Unless you cleaned them up and they somehow seated again. This cooling system is very fussy, with two thermostats and pressure relief valves. Were you running it with the hoses off, or on the thermostat hsg? Looked like they were off. It is very common for these engines to run hot on one side when running on a flushette, but you are running it in a bucket. The plastic relief valves have to move freely in those grommets as well, although yours seemed free in there. Those rubber cooling deflectors have to be pushed all the way in, cutting them off to fit will allow water to bypass and possibly overheat. But, the engine misbehaved before you had the head off. Did you get that new head gasket on correctly, couldn't really see, it only works properly when oriented with that tab on top, pointing outward. There is an arrow on the raised tab helping with orientation as well. I guess at this point, I would assemble the whole thing properly and try it again. You want the engine to get good and warm at low speeds so it will idle nicely, minimize smoke, and keep the plugs fairly clean. Once you raise the throttle, the added water pressure opens those relief valves allowing the engine to cool down a bit at higher RPM. The next step would be to start at the beginning, with the water pump. This is a complicated and fussy cooling system, not easy to work on those thermostats as well! But, everything must be right or the engine might overheat at low speeds on one bank or the other. Running the engine with those cooling hoses off might allow water to "short circuit" as well. Forgive me if I am repeating myself or advising things you have already done. I just don't want you fixing something that may not be broken, or making inaccurate conclusions. That crust in the water cover is pretty normal for salt water use, and rarely is an issue. That little scoring is normal for these engines as well.
taking the hoses off should see it almost instantly cool down, if so that tells us its again the t stat housing thats the issue. the deflectors are usually a little long and need to be cut on most occasions. i saw no evidence of water entering the cylinders. agree he needs to check the pump, but also needs to figure out why its idling so low, which will make it overheat as well!
Should use Permeates high tack on those gaskets. It works wonder to prevent leaks, A must for all paper gaskets especially on two strokes. Racer trick from jets koi racing.
good video! i have a 78 evinrude that needs a idle adjusted. hard to find videos showing how to do it. but i learned alot with your video on how the cooling system actually works.
I had a 71 ,85 hp Evinrude and it was great engine, check your impeller and your anodes and then run it in a barrel of flushing agent to clean out the salt and corrosion in the water jackets.
Thermostats in saltwater crust up. Pour boiling water into the housing from one of the hoses, and those stats will pop open. If you run it once a week they work all season. But every spring they will get stuck and the engine will over heat until u get them to pop the crust off.
I’ve got the same 175 but 98 model. No wood in the transom! 90 Hp spl. Seems the port bank always runs a little warmer than starboard. I’ve got that daisy chain going on with my switches on the center console and had to by pass directly to battery. I’d like to find OEM. Any sources?
Aaron, what did you use to get the head off? I have a similar engine but it is older and I want to remove the heads, but I am afraid I may break some head bolts. Any suggestions? Thanks.
the deflectors would only make it overheat at HIGH speed, not low. these t stat housings suffer from an air pocket that makes it so the t stat/s never open. we modify them by cutting a small notch in both, but you need to understand how this cooling system works. the STB head does NOT get its water 1st. they both do. usually the stb head is warmer since its higher up. by allowing much more flow, you are essentially negating the t stats at low speed, giving you a false reading. when taking the head temp, its done on the flat spot on TOP of each head, not in the middle or wherever. because the motor keeps stalling and occasionally sneezes, i'd make sure the carbs are really clean as well. what happens when you hit the primer does it pick up rpm?
Bad idea no thermostat motor will not warm.up enough 2 bad job cleaning up rust motor appears to be used in saltwater alot and not flushed with fresh water when pulled out
WHAT HAPPENS WHEN YOU DON'T FLUSH YOUR ENGINE WITH FRESH WATER AFTER BEING IN THE SALT CHUCK!~NO THERMOSTATS,BAD IDEA ENGINE WILL NEVER GET UP TO OPERATING TEMP AND WON'T RUN EFFICIENTLY OR ECONOMICAL!
Great video! Just wanted to comment on an observation. Your engine is running extremely lean. That hesitation, or sneeze, you hear at idle is a lean sneeze. This is usually due to a dirty carb. Running like that for a while can cause you lose a cylinder because if its running lean on fuel, its also running lean on oil. Just something to look into. Keep up the good work!
Edited/revised.
Glad to see the water diverters were checked. If you were doing one head, you should do both.
Deleting the thermostats does not solve your overheat problem, it just multiplies the complications with the motor.
Definite strong possibility of cold seizing engine damage due to pistons getting warmer faster than engine block/cylinder and locking up motor. Thermostats regulate temperature to prevent this.
Motor will run rough in more situations and will not idle as well.
Possibly will overheat engine in certain situations during idle as there is no backpressure to keep the water around the block and cylinder walls to evenly distribute the cooling water.
OK, a few things to think about here. First, both of those thermostats were blown open, NG. Unless you cleaned them up and they somehow seated again. This cooling system is very fussy, with two thermostats and pressure relief valves. Were you running it with the hoses off, or on the thermostat hsg? Looked like they were off. It is very common for these engines to run hot on one side when running on a flushette, but you are running it in a bucket. The plastic relief valves have to move freely in those grommets as well, although yours seemed free in there. Those rubber cooling deflectors have to be pushed all the way in, cutting them off to fit will allow water to bypass and possibly overheat. But, the engine misbehaved before you had the head off. Did you get that new head gasket on correctly, couldn't really see, it only works properly when oriented with that tab on top, pointing outward. There is an arrow on the raised tab helping with orientation as well.
I guess at this point, I would assemble the whole thing properly and try it again. You want the engine to get good and warm at low speeds so it will idle nicely, minimize smoke, and keep the plugs fairly clean. Once you raise the throttle, the added water pressure opens those relief valves allowing the engine to cool down a bit at higher RPM.
The next step would be to start at the beginning, with the water pump.
This is a complicated and fussy cooling system, not easy to work on those thermostats as well! But, everything must be right or the engine might overheat at low speeds on one bank or the other. Running the engine with those cooling hoses off might allow water to "short circuit" as well. Forgive me if I am repeating myself or advising things you have already done. I just don't want you fixing something that may not be broken, or making inaccurate conclusions. That crust in the water cover is pretty normal for salt water use, and rarely is an issue. That little scoring is normal for these engines as well.
taking the hoses off should see it almost instantly cool down, if so that tells us its again the t stat housing thats the issue. the deflectors are usually a little long and need to be cut on most occasions. i saw no evidence of water entering the cylinders. agree he needs to check the pump, but also needs to figure out why its idling so low, which will make it overheat as well!
This is a top notch video, EXACTLY I was looking for. Thank you so much for taking the time stranger
Should use Permeates high tack on those gaskets. It works wonder to prevent leaks, A must for all paper gaskets especially on two strokes. Racer trick from jets koi racing.
Sorry Permatex High Tack
I think manual says put head gaskets in dry
good video! i have a 78 evinrude that needs a idle adjusted. hard to find videos showing how to do it. but i learned alot with your video on how the cooling system actually works.
The idle adjustment isn't on the carbs
You'll be adjusting the screw on the big throttle/timing lever to advance the throttle/timing to adjust idle.
Port wine is red and has the same number of letters as left!😎
I had a 71 ,85 hp Evinrude and it was great engine, check your impeller and your anodes and then run it in a barrel of flushing agent to clean out the salt and corrosion in the water jackets.
Had the same motor but 150 v6 I did the same thing, cleaned the block and heads ran another 3 years
They make this things called wire brushes,
Also clr could help
I'd definitely start with fine tuning the ignition and fuel timing after going through the carbs. That extra heat could be from being lean too
Thermostats in saltwater crust up. Pour boiling water into the housing from one of the hoses, and those stats will pop open. If you run it once a week they work all season. But every spring they will get stuck and the engine will over heat until u get them to pop the crust off.
do you rinse the engine out with fresh water after you use the engine in salt water?
I’ve got the same 175 but 98 model. No wood in the transom! 90
Hp spl. Seems the port bank always runs a little warmer than starboard. I’ve got that daisy chain going on with my switches on the center console and had to by pass directly to battery. I’d like to find OEM. Any sources?
Aaron, what did you use to get the head off? I have a similar engine but it is older and I want to remove the heads, but I am afraid I may break some head bolts. Any suggestions? Thanks.
Where’d you get that boat cover?
Barnicle Buster. Take the lower unit off and thermostats out. Get a fountain pump and a tote. Let it run all night. You're welcome.
the deflectors would only make it overheat at HIGH speed, not low. these t stat housings suffer from an air pocket that makes it so the t stat/s never open. we modify them by cutting a small notch in both, but you need to understand how this cooling system works. the STB head does NOT get its water 1st. they both do. usually the stb head is warmer since its higher up. by allowing much more flow, you are essentially negating the t stats at low speed, giving you a false reading. when taking the head temp, its done on the flat spot on TOP of each head, not in the middle or wherever. because the motor keeps stalling and occasionally sneezes, i'd make sure the carbs are really clean as well. what happens when you hit the primer does it pick up rpm?
What was the end result? Water test . Did it still overheat?
140 is about right. When you get over 160 you have problems.
I have a '73 Mercury 1550. Dreading this!🤣
Merc 1550? In 73 there was a 1500. However your engine does not have a Thermostat
Lack of routine maintenance! Your heads will look the same too
Youre thermostats are stuck OPEN how tf is it overheating.
Water coming in the bottom!
flush out motor with clean water and muffs after each use
I would have sandblasted with silicone beads.
Bad idea no thermostat motor will not warm.up enough 2 bad job cleaning up rust motor appears to be used in saltwater alot and not flushed with fresh water when pulled out
I would of pull the cyln head while @ it. prolly reveal that knock.
No you need the thermostat
Formagasket not silicone
WHAT HAPPENS WHEN YOU DON'T FLUSH YOUR ENGINE WITH FRESH WATER AFTER BEING IN THE SALT CHUCK!~NO THERMOSTATS,BAD IDEA ENGINE WILL NEVER GET UP TO OPERATING TEMP AND WON'T RUN EFFICIENTLY OR ECONOMICAL!