Question for 1991 Sea-Doo XP / 587 About Cooling Flow Rate

[MAL]

I’m troubleshooting an overheating issue on my 1991 XP with the 587 engine. The pisser out the back looks weak, but I am not sure what normal looks like on these old skis. When I remove the hoses from the exhaust pipe and the head, the pisser streams are about 2–3 inches at idle and 3 feet when revved). The ski only overheats on long runs over 30 minutes or so. Is there a flow rate for this test?


Also, more importantly, is there a flow rate measurements from the cooling water discharge hose that exits the head and goes into the exhaust at the through-hull fitting?



I’m trying to determine whether my issue is a restriction in the cooling passages or something else, and having a baseline “normal” flow rate would help me confirm if water flow is the problem.


If I am looking at this completely backwards just let me know how I should proceed with an over heating diagnosis...Thanks

 

[mikidymac]

No, there is no flow rate spec.
If you have cooling water flowing you should not overheat.
How do you know it is overheating?
Step 1 would be a compression test. Low compression, blow-by and running lean can all cause overheating.
Step 2 make sure all your cooling hoses are routed correctly and clear.

 

[MAL]

No, there is no flow rate spec.
If you have cooling water flowing you should not overheat.
How do you know it is overheating?
Step 1 would be a compression test. Low compression, blow-by and running lean can all cause overheating.
Step 2 make sure all your cooling hoses are routed correctly and clear.

It gets hot to the touch on the head and starts running rough. The temp sensor is broke so I am looking for another to replace it with. I did pull the head and there is a score line that appears to be at the ring end gap location. The score is new because when I got the ski it had been honed with cylinders that were out of round. I used a fixed hone and got it straight, barely within specs. I suppose I could have a blow by issue, but it runs great until it gets hot. I haven't checked the compression yet because my compression gauge is junk.

 

[MAL]

This was a basket case when bought it so the cooling line routing is a good thing to double check. I think it is all correct, but the flow chart in the manual looks a little different than what my ski looks like. I have a pisser off the top of the cylinder head. The manual doesn't show that in the image of the flow chart. Was that an after thought on these to help cooling the engine?

 

[mikidymac]

No, Seadoo changed the cooling routing a few different times on the 587. The head pisser is later and from the factory.

You can’t fix an out of round cylinder with a hone, sounds like you are out of spec and will get blow by, overheating and seizures which is what is sounding like with the scoring.

 

[MAL]

No, Seadoo changed the cooling routing a few different times on the 587. The head pisser is later and from the factory.

You can’t fix an out of round cylinder with a hone, sounds like you are out of spec and will get blow by, overheating and seizures which is what is sounding like with the scoring.

I used a fixed hone like this one, Lisle 15000 Engine Cylinder Hone, 3" - 4-1/4" Range | ToolDiscounter I know it is not the same as going to a machine shop, but I used a bore gauge and watched the progress it straighted pretty good but by the time it cleaned up it was at the outer limit of spec. I don't remember what the numbers were but the pistons are as loose as allowed by Seadoo

 

[MAL]

No, Seadoo changed the cooling routing a few different times on the 587. The head pisser is later and from the factory.

You can’t fix an out of round cylinder with a hone, sounds like you are out of spec and will get blow by, overheating and seizures which is what is sounding like with the scoring.

In the PTO cylinder it has 139PSI and it the mag cylinder it has 145. I borrowed a gauge and I was told that it reads a little lower than what it actually is. I am definitely not happy with those numbers after just 2 years of riding it, but is that enough to cause over heating or did over heating cause the low compression?

 

[etemplet]

Those numbers are not causing your overheating. I'd say you have a cooling water flow issue. So when you removed the cylinder you cleaned any debris out of the water channels. I know the fittings on the cooling system are specific sizes and you have have one that is too large or too small (they are numbered). I'll look through my pictures but I have one ski where the outlet port at the back of the engine dead ends and only the flush is connected.

 

[etemplet]

A few pictures may help. This is from my 1996 SPI 587. All I got sorry.







This one is a 1995 SPX

 

[MAL]

Those numbers are not causing your overheating. I'd say you have a cooling water flow issue. So when you removed the cylinder you cleaned any debris out of the water channels. I know the fittings on the cooling system are specific sizes and you have have one that is too large or too small (they are numbered). I'll look through my pictures but I have one ski where the outlet port at the back of the engine dead ends and only the flush is connected.

I did clean out everything that I saw. I used air and water in the tune pipe and water jackets, but it seems that I missed something. How many fittings are there that are designed to control water flow. I know the elbow into the tune pipe is there to control back pressure in the exhaust and cool the pipes, but it doesn't seem like that would cause overheating if plugged or wrong size. Well...maybe it would cause the preheated water in the pipe to enter the engine hotter than it is supposed to be. The parts schematic doesn't show what size these fitting are supposed to be. Where can I find that info?

 

[Grim]

I had the same issue, I checked every hose one at a time and found nothing, It turns out my issue was the head, it had a small leak and was causing a flow issue inside the engine. I say this because I learned a lot. One thing that sticks out is the metered connector for the head. I am not very familiar with all tech specs of your machine but mine had a metered connector at the head that controlled flow to the engine. All it is is adapter form hose to the head but it is different on the inside. It has a small hole and if anything is to get clogged I believe that would be it. Now I am not sure but the last picture , on the right side may be a metered connector to the head. Have you taken that off the head and ran water through it to verify it isn't clogged? Even if it isn't metered it could be clogged. Just a suggestion.

 

[etemplet]

Do you have aftermarket exhaust or stock? I'm not used to the term "tuned pipe" I would suggest riding the ski with the seat off and locating the point where it is getting hot "Heat flows from hot to cold" so the hottest spot is the problem. A laser pointer thermometer would be helpful. Is the cylinder drain clear? I've seen a lot of build up on the bottom section near the drain.

As far as fitting size you can look on the parts schematic and it will tell you the size. As @Grim stated you'll have to look deeper. You'll find it. Here is a particluarly ugly head.

 

[MAL]

I had the same issue, I checked every hose one at a time and found nothing, It turns out my issue was the head, it had a small leak and was causing a flow issue inside the engine. I say this because I learned a lot. One thing that sticks out is the metered connector for the head. I am not very familiar with all tech specs of your machine but mine had a metered connector at the head that controlled flow to the engine. All it is is adapter form hose to the head but it is different on the inside. It has a small hole and if anything is to get clogged I believe that would be it. Now I am not sure but the last picture , on the right side may be a metered connector to the head. Have you taken that off the head and ran water through it to verify it isn't clogged? Even if it isn't metered it could be clogged. Just a suggestion.

The pictures are not my ski, but the hose on the right is the tell tail hose(pisser) I haven't had time lately to look at it. My head has that tell tail and an exit hose that goes back to the through hull exhaust fitting. If that exit hose was restricted I suppose it would cause a slow overheat problem. All the cooling water enters the exhaust manifold and is preheated in the pipe before it is sent into the engine...back through the manifold I think. How did you find the leak in the head? Was it a crack, gasket, internal or external? I could try a pressure test on the water jackets.

 

[MAL]

Do you have aftermarket exhaust or stock? I'm not used to the term "tuned pipe" I would suggest riding the ski with the seat off and locating the point where it is getting hot "Heat flows from hot to cold" so the hottest spot is the problem. A laser pointer thermometer would be helpful. Is the cylinder drain clear? I've seen a lot of build up on the bottom section near the drain.

As far as fitting size you can look on the parts schematic and it will tell you the size. As @Grim stated you'll have to look deeper. You'll find it. Here is a particluarly ugly head.

I have a stock exhaust. My understanding of a tuned pipe is that it's designed to have the proper back pressure for the ski to run properly. The pipes shape is part of it, but also the amount of water that is injected directly into exhaust determines how much back pressure it has. My understanding about back pressure is that if there were no back pressure the fuel would go into cylinder and straight out the exhaust port during the time when both ports are open. I do know for a fact that these things run like sh*t when there is an exhaust leak. The cylinder drain is where I get a little confused The water exits the top of the head and the cylinder drain at the same time as far as I can tell. I would guess that if either is restricted it would run hot. That may be a more likely suspect being on the bottom of the cooling system and having a smaller exit fitting. Hopefully I will get some time to look at it next week.

 

[mikidymac]

I have a stock exhaust. My understanding of a tuned pipe is that it's designed to have the proper back pressure for the ski to run properly. The pipes shape is part of it, but also the amount of water that is injected directly into exhaust determines how much back pressure it has. My understanding about back pressure is that if there were no back pressure the fuel would go into cylinder and straight out the exhaust port during the time when both ports are open. I do know for a fact that these things run like sh*t when there is an exhaust leak. The cylinder drain is where I get a little confused The water exits the top of the head and the cylinder drain at the same time as far as I can tell. I would guess that if either is restricted it would run hot. That may be a more likely suspect being on the bottom of the cooling system and having a smaller exit fitting. Hopefully I will get some time to look at it next week.

Very solse but not back pressure. Back pressure has nothing to do with it, on a 2-stroke it is the sonic wave that scavenges and keeps the air/fuel in the cylinder and the pipe along with the heat of the pipe changes that sonic wave.