90 yamaha overheating(1990)

Maycen

Recruit
Joined
Oct 24, 2004
Messages
1
First let me start by thanking whomever is responsible for this site it is quite informational for us novice "boat mechanics"(and I say that lightly)<br />I have, as you requested, researched the site to see if I could find the solution to my problem before i posted and there was some vague references to this but I could not find what I should do now.<br />It started with an overheat alarm going off and to make it quicker i will just list what i have done - new Thermostat<br /> new impeller <br /> new water pump<br /> Then- new water jacket<br /> had the head cleaned and sand blasted<br /> all new bolts and gaskets to put it back together (because in taking it apart i broke a bolt the water jacket (from the thermostat housing) and broke one in the head!<br />All this and it wont run idle for five minutes without overheating. It is "peeing" but there was a clog of something when i first started it, which makes me beleive that it is somewhat clogged. I don't know how to flush it out properly to eliminate this and see if it is something else? :confused:
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 90 yamaha overheating(1990)

hello<br /> you did have the head off? did you surface the head? does your 90 have a pressure relief valve installed in the t-stat housing as well as the t-stat? if the valve leaks water pressure drops and overheat at idle speed will occur. have you used a thermo-melt stick or infared temp probe to determine if the sensor has failed and is it actually overheating. was the pump impeller replaced or the entire pump kit? I have a 115 that the port temp sensor triggers at 100 degrees. its a bad temp switch <br /> your engine temp switch should be on at 84-90*C.<br /> good luck and keep posting
 
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