Motor question

[Dr. Fish]

I own a '91 Yamaha 90hp 2-stroke. It runs like a top, but activates the "hot" alarm whenever I let it idle, or try and troll, for more than about 5 minutes. I was wondering if there is an intake screen that was plugged, or something I'm missing that could cure the problem. Thanks in advance!

[gjk1970]

Most motors do have inlet screens down on the lower unit but this summer I ran into this exact problem and it turns out my water pump broke a fin...Go to the easy part first check lower unit inlets that suck cold water if it is clear..Sounds like a water pump is in your near future..

[Dr. Fish]

Thanks for the help! Any ideas "about" what a water pump costs?

[wastewaterguru]

About $20 to $30 if you do it yourself. MAybe not even that much.

[1DIRTBALL]

Dr Fish, If you aren't able to solve the problem with your motor, try checking with Surface Tension on the Duluth forum. He seems to know more than most when it comes to outboards.

[delmuts]

dr. fish. lets us know what you find out! i have a 1990 90hp yam. on my ranger. thanks del

[Surface Tension]

Thanks Dirtball,

I'd agree the impeller is most likely the culprit. Being that the motor is a early 90's its good practice to replace the impeller anyway.

Its an easy repair and I'll quickly run through the proceeder but a manual wouldn't hurt to have and a aftermarket manual is fairly cheap at around 25 bucks or you can take on out at your public library for free.

Put the engine in gear then remove the prop.

Remove the nuts from the lower unit, you'll find them in the area of the cavitation plate. Now look for a plastic plug on the rear of the lower unit, its directly above the trim fin, remove the bolt and the fin should come off and the lower unit should drop but you might have to do coax it along. Don't pry between lower unit and the drive with anything. If it doesn't pull off then you or I are missing a nut or bolt that needs to be removed. I don't think you need to disconnect any shift linkage with that motor but thats just one more reason to have a manual for reference.

Once the lower unit is out you'll notice the drive shaft and a water tube{usually copper} At the base of the drive shaft is the water pump housing, take the top cover off carefully without damaging the gasket or o-ring. Under the cover is the impeller. Slide the impeller off the drive shaft. Note the direction the fins are spun, I've heard it doesn't matter which direction the fin are pointed with the new impeller because once the motor turns over they take their own Right position but I like to line them up.

You'll also have either a pin or a key of some type that keeps the impeller from spinning freely on the drive shaft, don't lose it. While you have the impeller off look for ant debris in the water port and it wouldn't hurt to blow them out. Also look at the surfaces inside the water pump housing for burnt on impeller {any other reason why you don't start any outboard with out it being in water} or gouges.

Now replace the impeller while lining up the pin or key.

Replace the top of the housing, if it has a gasket you can use and RTV silicone but don't put it on as to where it could overflow into the water pump.

Time to put the lower unit back on. Align the drive shaft and water tube and slide the lower unit back on, you shouldn't have to use force.