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2006 BF90 Cooling Issue

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dougp59

New member
Hi. Thanks for reading! My 90 hp had the following issues today, 05/24/2025 on the Fox Chain O'Lakes in northern Illinois.

1.) Intermittent Pee.
2.) Upon startup, the temperature gauge starts at zero. When warmed up, it hits 140 degrees and stays there. At low speed, it is under two grand, so there are no issues.
3.) At high speed over four grand, the overheating buzzer comes on after a while, even when the gauge still reads 140. I back off for a moment, the buzzer quiets, and I can throttle up again, but the buzzer comes back on a few moments later.
4.) I waited a moment and throttle back up to just around 3400. It ran fine for 10-15 minutes or so before the buzzer came back on again.
5.) It was peeing fine when I left the dock, but it was no longer when these issues started.
6.) Back at the dock, I let it sit for a good hour. Started the engine and let it warm up. After 10- 15 minutes, I used an infrared gun to check the temperature of the head at each spark plug. The top was 184, the other three got cooler as I went down to the last plug.

The outboard has a brand-new waterpump kit installed by an excellent marine mechanic.

Any tips are GREATLY appreciated.
 
Well....
It does sound like it may be getting hot and going into guardian (depower) mode. And your seeing the 184°f at the top plug certainly doesn't agree with your gauge. What temperature are you seeing at the bottom cylinder?

Not knowing where that gauge is plumbed to the cylinder head I would want to make sure that was done properly. If it isn't sampling from an area very near the overheat sensor then accuracy and "agreement" between the two will be suspect.


Why was the pump replaced? Was it running hot before that? Was the pee stream stopping?

Did the mechanic say anything about missing, broken off impeller vanes? If so, internal blockage is a distinct possibility.

The pee stream being good but then stopping might be a clue. It makes me think something happened. Either blockage as mentioned above or, maybe, the impeller drive key slipped and isn't turning the pump properly. It happens. The new kits should come with a new key but the area it sits in on the vertical shaft can be worn too and cause this to happen.

Even the VERY BEST mechanic can have a WHOOPSEE once in awhile or a new (or old) part can fail on him.

If it were mine I would want to pull the gearcase and make sure all is well with the pump and the installation including the water tube and it's upper grommet. If all looks as it should then doing some forced pressure backflushing to try and dislodge any blockage would be a good thing to do while the case and pump are off.

If you describe the problem to your mechanic, HE might want to get first crack at going back in and taking a look. Although, if there's nothing amiss in there he's going to charge you for the work and rightfully so.

But, continuing to run it without knowing why it's "saving itself" could cost you much, much more. Because, each time it gets hot enough to activate the engine protection system, that might not.be so great for it's health.

Sorry for the negative take on it but just giving my opinion.

Good luck.
 
Check thermostat to see it is clean and operating properly.

Did you install the full water pump kit or just the impeller ?
 
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