Heat Exchanger / Cooling issue

[390Express]

Source of the post BTW, no filter in the raw water side of the Walter unless a previous owner installed something inline before it. I don't think that impeller pieces would get stuck in the drive's exchanger but anything's possible.

500 rpm is way too low for the Walter. You need to find out what's causing the low rpm.

ECU is a MEFI 1 or 2 (I believe a 1, given the 1996 vintage) It was programmed by Arizona Speed & Marine. ASM and "Mefi Bob" are the only two people doing it, as far as I know. I don't know if ASM set the idle too low, or if the motor is trying to idle too low for other reasons. According to ASM, the ECU is a learning ECU, and receives data back from the rpm, IAC, etc., and "learns" the motor. I could try swapping ECUs to see if the erratic idle still exists with the stbd motor.

You believe there is a danger of hurting parts of the exh system, if the boat isn't ran long enough to make the manifolds hot? I shut them off before the manifolds become hot to the touch. I'm in the engine bay when I start and run it.

[bud37]

Source of the post You believe there is a danger of hurting parts of the exh system, if the boat isn't ran long enough to make the manifolds hot? I shut them off before the manifolds become hot to the touch. I'm in the engine bay when I start and run it

Consider this....exhaust gas temps are well over 1000F at initial start up......the rubber exhaust hose is dry with no cooling and it is rated at somewhere around 225F max depending on the quality of the hose, they wear out from the inside to the outside. Chances are if you have been doing this a fair bit then at the very least you will have to take the hoses apart and inspect for damage .

[390Express]

Source of the post

Source of the post You believe there is a danger of hurting parts of the exh system, if the boat isn't ran long enough to make the manifolds hot? I shut them off before the manifolds become hot to the touch. I'm in the engine bay when I start and run it

Consider this....exhaust gas temps are well over 1000F at initial start up......the rubber exhaust hose is dry with no cooling and it is rated at somewhere around 225F max depending on the quality of the hose, they wear out from the inside to the outside. Chances are if you have been doing this a fair bit then at the very least you will have to take the hoses apart and inspect for damage .

All understandable, but the exhaust is passing through a cooled exhaust manifold, through a 4" cooled riser extension, then a cooled riser, that has never been hot to the touch, before reaching the first rubber hose.

I've ran the boat twice, at two intervals of approximately 10 minutes, without the manifolds or rubber hoses ever getting warm to the touch. I can't see any way that the exh gas was ever over 225F, with the manifolds, hoses, and fiberglass elbows never getting warm.

[tomschauer]

The risers are raw water cooled. I personally would not run more than a minute knowing I had no flow. Those big exhaust hoses are quite pricey!

[390Express]

I think I found my cooling issue for the Port motor. There were two pieces of impeller stuck in the oil cooler. Hoping new impellers and cleaning/flushing the old pieces cure the issue.

[RGrew176]

Those impeller pieces could very well be the culprit. I hope this is the solution to your problem. Good luck.