The absolute best advice when buying a PWC or boat is to do a water test if you are paying a water ready price. You wouldn't buy a used car just by looking at it in a parking lot. Or at least you shouldn't. Even if you do a compression test and hear it start up and run out of the water doesn't mean it doesn't have issues in the water.
I wish I would have known before. I bought a 98 seadoo spx 787 recently and looked good, good compression, and ran good…out of water. Dropped it in the water and was hard to start after siting in the water for a bit, actually so hard to start my battery died and was stranded in the middle of the lake. Bottom end and top power was very weak, just ran like crap. I’ve done absolutely everything to try and get it running right and it still runs like crap. There’s nothing else I can think of that could be wrong with it so I handed over to a shop to figure it out. Lesson learned, water testing is mandatory next time. The pressure difference in water than out is crazy on boats and skis.
@@duckygang603 Would also be interested. Starting issues in water can actually be caused by dying starter or bad cables as well. But the other problems not, obviously.
Only a couple other things I'd suggest. Myself I'd definitely inspect for any kind of hull damage. Also a old seadoo mechanic told me to always water test any jetski. It can run good out of water but different in water. Hence a problem I had..... jetski ran great out of water. Would drop it in and would bog.... thought carbs maybe as most say..... found out once in the water. The stator wasn't producing the necessary spark once the jetski was under a load/the water.
I think you are wrong. If there is enough spark to run the engine smoothly, the extra load from running in water can't possibly be effected by the weakness of the stator. After all, if there is enough spark to ignite the fuel mixture, the strength of the spark can't vary the power of the explosion. You should test your compression, it is probably marginal.
@judgedayan9934 sooo when the spark is weak. How does any motor run? It may bog, sputter, backfire, ect correct? When the jetski is sitting in the driveway running a stator can keep up, running off a garden hose and be producing the necessary spark. Since a garden hose doesn't produce the same load floating in the air on a trailer. As a average 200 pound adult and the jetski having to break through the water with that weight sitting on it. That kinda load puts a strain on the stator to produce the necessary spark at higher rpms under that kinda load as opposed to the driveway. I hope that make sense. I did get a bill from the marina shop that charged me for stator replacement. If it was compression, I'm assuming I'd have a rebuild charge. But it's what the mechanic told me.
@@kevinrivard3875 You didn't understand what I said. Let me elaborate. the 12v battery does not supply power to the ignition coils and CDI that energizes the spark plugs with a boosted 30,000+ volts. The battery only powers the starter. When the starter spins the motor, the magneto (the stator is the non-moving part of the magneto that has magnetic induction coils) is energized to produce a much higher voltage that is directed to the CDI which continues to boost the voltage, from there the voltage is directed to the ignition coil for each spark plug. The ignition coil boosts the voltage to the level to fire the plugs. It is a fact that magnetos produce more voltage with more RPM. However, if the starter is strong enough to spin the motor to spin the magneto enough to produce spark voltage, the fuel will ignite and the engine runs. There is essentially no difference in power if the spark voltage is 25k volts or 100k volts (except that the life of the plugs is longer with higher voltage). As for the extra load in the water, since the engine is in direct drive with the impeller, there is a very slight load on the engine when the impeller must move water, it has nothing to do with the weight of the rider. However, if the starter (not the stator) is weak, maybe the extra load of the water could slow the turning of the motor so not enough voltage is produced to create a spark and the motor won't start. But once the motor starts and you give it a little gas, there is no effect on the stator because the ski is in the water.
The absolute best advice when buying a PWC or boat is to do a water test if you are paying a water ready price. You wouldn't buy a used car just by looking at it in a parking lot. Or at least you shouldn't. Even if you do a compression test and hear it start up and run out of the water doesn't mean it doesn't have issues in the water.
@@judgedayan9934 I agree in that spark is spark, and will ignite the mixture. If there was a situation where you didnt have spark only when in water, the most likely cause is the engine starting speed reduced by loaded impeller, which could be potentially a weak stator configuration or winding. SO start it out of water and send it till it breaks.
I like to pick up project ski. I prefer the Kawasaki 2 stroke 650 and 750 skis. I take a compression test, good battery, some mix basic tools to inspect them. My next favorite would be the Yamaha's. They tend to cost a bit more so for me the best bang for the buck is a Kawi. I avoid the Seadoos and Polaris. Seadoos are the worst to work on. The grey tempo fuel lines are notorious for clogging the fuel filters in the carbs. Out of all the Seadoos the 787 RFI with the fuel injection would the one to pick. Not to be confused with their Direct Injected engines which would be the bottom of the list. Other issues with the Seadoos are the DESS system, rotary valve engines shouldn't be converted to premix, the carbon ring seal and the fact you need a $300 alignment tool if you pull the engine. Saltwater corrosion is another thing to look for.
I just use my thumb for compression, and really unless there are signs of a bottom end overhaul I just plan for an overhaul, luckily these are not too bad to overhaul especially if crank good. I'd have to agree on the 787 RFI, absolute awesome engines and its too bad they did not continue their development. If you want economical yea Kawi and Yamaha, but BRP and Polaris provide the best bangs ;)
That’s a good question, and I bet it’s a common misunderstanding that compression means good seals. Good Compression DOES NOT mean good crank seals. Your correct in that leak down is the proper way to test for leaking crank seals. It requires sealing off the crankcase airtight which is much more of a chore than running a compression test.
Waterflow is for cooling only on these, like many other engines temp needs to stay under 200~ degrees Fahrenheit, we don't ever run them long enough to reach that temperature.
@@amphibiouspowersports9963 You are making a video for people who are too ignorant to know what to look for when buying an old cheap jetski that may even need some work. Those people see you run the engine without water and it probably wouldn't dawn upon them that you have to be very careful not to run it too long like that. The least you could have done is say explicitly, "It's ok to test and see if the engine starts, but don't run the engine too long without a hose." You would also have to note that the engine should be started before the water is turned on and the water turned off before killing the engine. (I have 2 old Sea Doos I bought cheap and fixed them up).
@judgedayan9934 you can run them for 30 seconds to a minute or so with no problems. Newbies are more likely to turn the water on at the house, walk over to the ski and try to start it. If the ski doesn't want to stay running they have to walk back over to the house to shut off the water. A lot more risk of backsliding the cylinders for someone new to Jet Skis.
lake test is always the best, but not always an option. They can be run out of water for a short amount of time- up until engine reached operating temp.
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The absolute best advice when buying a PWC or boat is to do a water test if you are paying a water ready price. You wouldn't buy a used car just by looking at it in a parking lot. Or at least you shouldn't. Even if you do a compression test and hear it start up and run out of the water doesn't mean it doesn't have issues in the water.
I wish I would have known before. I bought a 98 seadoo spx 787 recently and looked good, good compression, and ran good…out of water. Dropped it in the water and was hard to start after siting in the water for a bit, actually so hard to start my battery died and was stranded in the middle of the lake. Bottom end and top power was very weak, just ran like crap. I’ve done absolutely everything to try and get it running right and it still runs like crap. There’s nothing else I can think of that could be wrong with it so I handed over to a shop to figure it out. Lesson learned, water testing is mandatory next time. The pressure difference in water than out is crazy on boats and skis.
@@duckygang603 what ended up being wrong with it? what did the shop say?
@@duckygang603 Would also be interested. Starting issues in water can actually be caused by dying starter or bad cables as well. But the other problems not, obviously.
I’d love to see the newer (2004-2015) version of this exact video! More so interesting in that. Great educational video!
That was the most straight to the point and easy to follow advice I've seen. Thankyou.
Only a couple other things I'd suggest. Myself I'd definitely inspect for any kind of hull damage. Also a old seadoo mechanic told me to always water test any jetski. It can run good out of water but different in water. Hence a problem I had..... jetski ran great out of water. Would drop it in and would bog.... thought carbs maybe as most say..... found out once in the water. The stator wasn't producing the necessary spark once the jetski was under a load/the water.
I think you are wrong. If there is enough spark to run the engine smoothly, the extra load from running in water can't possibly be effected by the weakness of the stator. After all, if there is enough spark to ignite the fuel mixture, the strength of the spark can't vary the power of the explosion. You should test your compression, it is probably marginal.
@judgedayan9934 sooo when the spark is weak. How does any motor run? It may bog, sputter, backfire, ect correct? When the jetski is sitting in the driveway running a stator can keep up, running off a garden hose and be producing the necessary spark. Since a garden hose doesn't produce the same load floating in the air on a trailer. As a average 200 pound adult and the jetski having to break through the water with that weight sitting on it. That kinda load puts a strain on the stator to produce the necessary spark at higher rpms under that kinda load as opposed to the driveway. I hope that make sense. I did get a bill from the marina shop that charged me for stator replacement. If it was compression, I'm assuming I'd have a rebuild charge. But it's what the mechanic told me.
@@kevinrivard3875 You didn't understand what I said. Let me elaborate. the 12v battery does not supply power to the ignition coils and CDI that energizes the spark plugs with a boosted 30,000+ volts. The battery only powers the starter. When the starter spins the motor, the magneto (the stator is the non-moving part of the magneto that has magnetic induction coils) is energized to produce a much higher voltage that is directed to the CDI which continues to boost the voltage, from there the voltage is directed to the ignition coil for each spark plug. The ignition coil boosts the voltage to the level to fire the plugs. It is a fact that magnetos produce more voltage with more RPM. However, if the starter is strong enough to spin the motor to spin the magneto enough to produce spark voltage, the fuel will ignite and the engine runs. There is essentially no difference in power if the spark voltage is 25k volts or 100k volts (except that the life of the plugs is longer with higher voltage). As for the extra load in the water, since the engine is in direct drive with the impeller, there is a very slight load on the engine when the impeller must move water, it has nothing to do with the weight of the rider. However, if the starter (not the stator) is weak, maybe the extra load of the water could slow the turning of the motor so not enough voltage is produced to create a spark and the motor won't start. But once the motor starts and you give it a little gas, there is no effect on the stator because the ski is in the water.
The absolute best advice when buying a PWC or boat is to do a water test if you are paying a water ready price. You wouldn't buy a used car just by looking at it in a parking lot. Or at least you shouldn't. Even if you do a compression test and hear it start up and run out of the water doesn't mean it doesn't have issues in the water.
@@judgedayan9934 I agree in that spark is spark, and will ignite the mixture. If there was a situation where you didnt have spark only when in water, the most likely cause is the engine starting speed reduced by loaded impeller, which could be potentially a weak stator configuration or winding. SO start it out of water and send it till it breaks.
My advice is making sure you have some alcohol around. You are going to need it when you start working on jet skis.
Runs great…. Pass! 😂
You can tell if you have bad bottom end seals just not quickly you place a block off plate on the exhaust and pressure test the crank case
Have to block off intake too.
Great video. very informative
Interesting video definitely vote for a part II
I like to pick up project ski. I prefer the Kawasaki 2 stroke 650 and 750 skis. I take a compression test, good battery, some mix basic tools to inspect them. My next favorite would be the Yamaha's. They tend to cost a bit more so for me the best bang for the buck is a Kawi. I avoid the Seadoos and Polaris. Seadoos are the worst to work on. The grey tempo fuel lines are notorious for clogging the fuel filters in the carbs. Out of all the Seadoos the 787 RFI with the fuel injection would the one to pick. Not to be confused with their Direct Injected engines which would be the bottom of the list. Other issues with the Seadoos are the DESS system, rotary valve engines shouldn't be converted to premix, the carbon ring seal and the fact you need a $300 alignment tool if you pull the engine. Saltwater corrosion is another thing to look for.
I just use my thumb for compression, and really unless there are signs of a bottom end overhaul I just plan for an overhaul, luckily these are not too bad to overhaul especially if crank good.
I'd have to agree on the 787 RFI, absolute awesome engines and its too bad they did not continue their development. If you want economical yea Kawi and Yamaha, but BRP and Polaris provide the best bangs ;)
Awesome video!
Would a leaky seal/bottom end in a 2 stroke be revealed by doing a compression test? or maybe a leak down test? if there's such a thing for jet skis
That’s a good question, and I bet it’s a common misunderstanding that compression means good seals.
Good Compression DOES NOT mean good crank seals.
Your correct in that leak down is the proper way to test for leaking crank seals. It requires sealing off the crankcase airtight which is much more of a chore than running a compression test.
@@amphibiouspowersports9963 much thanks for your reply!
You know jetskis? Why are you running the engine without water flow?
Waterflow is for cooling only on these, like many other engines temp needs to stay under 200~ degrees Fahrenheit, we don't ever run them long enough to reach that temperature.
@@amphibiouspowersports9963 You are making a video for people who are too ignorant to know what to look for when buying an old cheap jetski that may even need some work. Those people see you run the engine without water and it probably wouldn't dawn upon them that you have to be very careful not to run it too long like that. The least you could have done is say explicitly, "It's ok to test and see if the engine starts, but don't run the engine too long without a hose." You would also have to note that the engine should be started before the water is turned on and the water turned off before killing the engine. (I have 2 old Sea Doos I bought cheap and fixed them up).
@judgedayan9934 you can run them for 30 seconds to a minute or so with no problems. Newbies are more likely to turn the water on at the house, walk over to the ski and try to start it. If the ski doesn't want to stay running they have to walk back over to the house to shut off the water. A lot more risk of backsliding the cylinders for someone new to Jet Skis.
Of course warer flowing thru it?
lake test is always the best, but not always an option. They can be run out of water for a short amount of time- up until engine reached operating temp.