'99 Ski GT40, reduced water flow and port side overheating

[SilentSeven]

.... I think the total water being pumped is inadequate and thus most of it is going to one side (though I must admit, I don't know why)....

This makes a lot of sense.

[JP75]

Did you ever get this figured out? I'm wondering what the problem was. My gt-40 port manifold got very hot last week. I had to order new exhaust hoses, and have checked for blockages throughout. A new impeller, T-stat, riser gaskets to see if any of those caused it, but they all looked pretty good. Will check water flow when I get it put back together.


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[SilentSeven]

Oddly, I'm now seeing this on my GT-40. +1 if anyone ever solved this. I am going to go and re-check my raw water pump.

[functionoverfashion]

FWIW, I had a similar problem in my old boat. It had dual exhausts, though, all the way through the transom. I believe the problem was some minor blockage in the exhaust on one side, causing back pressure at idle. Mine would only get hot at idle, never when running at any speed - even 1,000 - 1,200 RPM. Engine was a GT-40. I went through the entire system front to back except for the mufflers which, in that boat, were glassed in under the floor.

The exhaust hoses can also collapse internally if they get hot - that's one thing to look at if everything up front is OK. The riser gaskets also have a passage blocked intentionally and sometimes those get put on backwards BUT that's not the problem if it didn't start after a riser gasket replacement.

One other thing to look at is where the exhaust hose meets the riser. The water passages there aren't that big and if the hose got hot it could have formed into those grooves a bit, restricting flow to some extent.

[SilentSeven]

Hmmm. Interesting. Similar symptoms. I currently have my muffler out (2 into 1 hull hugger) and I can tell it has a broken internal baffle - I can see it flopping in the unit. Not so sure that could cause this but not ready to ready to rule it out. There are some threads on CC fan about cutting open the muffler to repair but none of them speak to exactly what I am seeing.

My plan of action at the moment is to retighten all clamps to make sure I'm not sucking air + check manifold for any obvious blockage. If that doesn't fix it, I may then go after the muffler.

[srock]

I wonder if you can run a camera through the system to look for blocks. I see plumbers do it all the time.

[functionoverfashion]

Hmmm. Interesting. Similar symptoms. I currently have my muffler out (2 into 1 hull hugger) and I can tell it has a broken internal baffle - I can see it flopping in the unit. Not so sure that could cause this but not ready to ready to rule it out. There are some threads on CC fan about cutting open the muffler to repair but none of them speak to exactly what I am seeing.

My plan of action at the moment is to retighten all clamps to make sure I'm not sucking air + check manifold for any obvious blockage. If that doesn't fix it, I may then go after the muffler.

I'm not familiar with the internals of those mufflers. Can you flip them around so the port and starboard sides are reversed? If so, maybe the issue would go to the other side if that's what's causing it. I wouldn't be surprised if a broken baffle is the issue, especially if you've thoroughly checked the supply side.

[SilentSeven]

I wonder if you can run a camera through the system to look for blocks. I see plumbers do it all the time.

That's a great idea. Sadly, I don't have that sort of camera. Have to see if any buddies do.....

I'm not familiar with the internals of those mufflers. Can you flip them around so the port and starboard sides are reversed? If so, maybe the issue would go to the other side if that's what's causing it. I wouldn't be surprised if a broken baffle is the issue, especially if you've thoroughly checked the supply side.

Can't flip as one side is tapered to the hull. I think I'm going to double check all my supply side first and then come back to this if it's still a problem. I agree it's a suspect item. Not hard to remove the muffler.

[beamons]

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[SilentSeven]

annnnndddd...my run hot problem was solved by clamping all the hoses and verifying the strainer was tight. Runs nicely at 160 now on both throttle and idle.

[srock]

You were sucking air! I was expecting something more dramatic. Its interesting that it showed up on one side.

[SilentSeven]

My guess - that side already seems to be on a diminished flow for reasons documented elsewhere. When the system is working at full capacity, it's fine. But when you have some flow volume issue, it's the first part to show problems. But yeah, glad it's resolved and wasn't something more complicated.

[Fvmako]

The strainer was not tight and it was that simple? The strainer bowl itself or the intake and outlet fittings &clamps?

[SilentSeven]

Can't say exactly what it was. I just tightened up all the intake clamps between the thru-hull and the raw water pump. A few of them were less than completely snug.

[JayG80]

https://www.planetnautique.com/vb5/f...starboard-side