YAMAHA overheat fixed

pine island fred

Lieutenant Junior Grade
Joined
Dec 20, 2002
Messages
1,144
This fix might have been discussed before and I missed it so I thought I would throw this out there.
Been an on going problem with a friends 90, 200 hp. 2 stroke. Motor started overheating and the first attempt to fix was naturally an impeller. He said it looked good and replaced it anyway like we all would. That did not fix it and this is where the pulling the hair started. Would overheat, then run normal for awhile, no rhyme or reason. Peed out the witness hole real good so we figured there was good water flow. New thermostats, pressure relief valve,taking the heads off and using acid, still overheated! I talked him into removing the thermostat houseings , running the motor and seeing what kind of water was running thru the blocks. Well there was none, just steam and the pee hose was running strong.
We dropped the leg to see if he might have missed or damaged the discharge pipe when he last installed the leg but that looked good and we used a garden hose to spray up the pipe and found good water flow. We took the pump apart and something did not look right.
Inside the plastic pump housing is an eccentric stainless steel cup or insert that the impeller rides in. About 1/4 around the circumfrance of the cup is a beval to allow the water out of the pump. The cup had actually rotated in the housing to a point where it locked up in the eccentric to severely restricted water flow. Was enough to pee real good out the hole but that as far as the water that made it by would go. The cup has 2 bent up tabs , 90 degs. apart that index into the housing base. The pump housing had 2 receptical for these index tabs that are 180 degs. apart. The old cup was so damaged removing it from the housing that he bought a new one and a new pump housing that has the correct index holes.
Watching him install the pump over the impeller , he used the method of rotating the housing over the impeller in the direction of rotation where as I push the vanes into the housing. I guess either method works but sure enough on looking down the discharge pipe, the the cup had rotated enough to block off the discharge. No-see-ums jumped us so we had to call it quits but I am certain that once installed correctly the overheat problem will be rectified.
Sorry for being long winded, wanted to share this while it was still fresh in my mind. regards FRED
 

BruceAML

Petty Officer 1st Class
Joined
Feb 26, 2007
Messages
371
Re: YAMAHA overheat fixed

You were not long winded, just being very informative. Thank you for taking the time to explain things.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: YAMAHA overheat fixed

no worries Fred.
thanks for the refreshing beverages though :)
anytime your at the crab let me know.
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: YAMAHA overheat fixed

Glad you finally found the problem, and shared the info for anyone else that may have similar symptoms. I applaud you!
 

pine island fred

Lieutenant Junior Grade
Joined
Dec 20, 2002
Messages
1,144
Re: YAMAHA overheat fixed

Just an update. It did fix the problem and I am a HERO. My money will be no good at the tavern tonight.
MikDee, could not agree with you more, at least in saltwater. My friends I/O is sitting in my yard right now getting a new engine ( VOLVO 290 duoprop.). Any tips on installing a new harmonic balancer ? Right now he has it 1/2 way on and it wont go any farther. Thought about putting it in the oven and heating it but it has rubber parts. regards FRED
 

sdsaw

Petty Officer 2nd Class
Joined
Aug 19, 2007
Messages
188
Re: YAMAHA overheat fixed

Good going on the overheating fix! This will sure to help someone else in the future. ;)
If that harmonic balancer is sliding onto a straight shaft, try removing the key and see if it slips on. If it does then flat file the key and check the key slot in the balancer. Also check the height of the key, some times the key would be too tall for the keyway in the pulley. If it doesn't slide on without the key installed, suspect the shaft needs a little deburring.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: YAMAHA overheat fixed

they make a tool for installing the balancer. DO NOT hammer it on.
a tool can be made with a piece of all thread,2 washers and a nut.
thread the all thread into the crank,install the balancer,then grease the 2 washers and slip them on the all thread,tighten the nut until the balancer bottoms while holding the crankshaft.
but most larger auto parts stores will rent the tool.
 

pine island fred

Lieutenant Junior Grade
Joined
Dec 20, 2002
Messages
1,144
Re: YAMAHA overheat fixed

Welcome back rodbolt, any warrants for your arrest out there south of the boarder? We removed the dampener with the correct tool and I stood by watching him as he pulled the thing on with the big bolt and washer. Slid right on!
While I am here, did you say that you dont flush your motors? Admit I had a few at and before the CRAB and my memory might be skewed about our conversation. regards FRED
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: YAMAHA overheat fixed

Do I flush my motors ?
why yes, well maybe, if I remember :):)
dont always do what I do, follow the manufactures reccomendations :).
 

scottlsmith1

Recruit
Joined
Apr 4, 2010
Messages
1
Re: YAMAHA overheat fixed

I know this thread is quite aged, but thanks for the detailed info. I have tried everything to fix the same issue. Will try this tomorrow.
 
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