Question for outboard mechanics.

I'll post this on the mechanical board also but I know you all can help.
I've had the water pump changed on my Yamaha F90. It just don't pee as hard as it used to. (I know the feeling). I've taken it back to the shop twice. They agree that it should be peeing harder but cant tell why it isn't. The pump and impeller is new and has been changed twice. The mechanic told me that there must be some kind of build up inside of the engine.

My question is: Is there anything I can run through the engine to clean the water jacket? Is there any way to tell if something is restricting the flow of water? Thanks.

I am newly registered member been reading for a while. I have a 25 HP that had the same problem, it was the 90 degree nipple that the pee tube go on, took it off and blew a bunch of gunk out of it, works fine now! Took me two water pumps to figure that out. Hope this helps.

Speck, aren't you the fella posted that had the impeller changed recently and had no flow at all and a heat warning horn going off?

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Originally Posted by kazualobzerver

Speck, aren't you the fella posted that had the impeller changed recently and had no flow at all and a heat warning horn going off?

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Yep, that was the first impeller.

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Originally Posted by Jerkey Log

I am newly registered member been reading for a while. I have a 25 HP that had the same problem, it was the 90 degree nipple that the pee tube go on, took it off and blew a bunch of gunk out of it, works fine now! Took me two water pumps to figure that out. Hope this helps.

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Great advice. I'll check it. Thank You. Also, Welcome to the board.

Spec, if cleaning the hose at the outlet doesn't fix it, try this. I jerry rigged a bunch of fittings together to neck down a garden hose to some fish aquarium tubing. At the time I was a new dad and didn't have the money for a mechanic! Anyway, I hooked up to the garden hose and backflushed through the exit hole. I let it run slow for a couple of minutes and it worked for me. Also tried on a friends Yamaha 200 V Max and it worked. Good luck.

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Originally Posted by LOZslabhunter

Spec, if cleaning the hose at the outlet doesn't fix it, try this. I jerry rigged a bunch of fittings together to neck down a garden hose to some fish aquarium tubing. At the time I was a new dad and didn't have the money for a mechanic! Anyway, I hooked up to the garden hose and backflushed through the exit hole. I let it run slow for a couple of minutes and it worked for me. Also tried on a friends Yamaha 200 V Max and it worked. Good luck.

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Good idea!!! I'll give it a try. Thanks

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Originally Posted by speckhunter

Great advice. I'll check it. Thank You. Also, Welcome to the board.

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While you have the nipple off run the motor, this will give you a much larger output hole to flush out anything in the block.