Whats the root cause of the problem?

[Joe Fisherman]

89 60hp john brand new H2O pump/impeller brand new stat H2o head passages/deflectors clean.Will run for hours and hours at 75% throttle great.Soon as you run 95- 100% throttle instant overheat buzzer and S.L.O.W mode???????? Water coming from tell-tale and out 2 exhaust ports fine...

 

[Walker]

Re: Whats the root cause of the problem?

I'd do 2 things. First I'd decarb the motor. Carbon buildup insulates the metal and prevents proper heat transfer and dissipation. Second, I'd check the sensor to make sure its tripping at the right temp.

 

[Joe Fisherman]

Re: Whats the root cause of the problem?

Any other advice???

 

[ob]

Re: Whats the root cause of the problem?

I'll second Walkers advice on assuring that the overheat alarm you are getting is bonafide.Did you feel the head covers with the engine cover removed after the alarm episode?Should be able to keep your hand on heads for several seconds before it gets unconfortable.If it is simply too hot to touch ,you are likely overheating .You can obtain a thermo melt stik of 163 degree from your dealer to check with.Confirm the overheat and we can go from there.<br /><br />Are you using the VRO on this engine or has it been bypassed?What leads you to believe it is going into the S.L.O.W. mode when alarm sounds.Do the rpms reduce to around 2500?Did you have to shut the engine off to reset it and resume operation at lower speeds(above 2500 rpm)?Just want to make sure we're chasing an overheat problem and not a fuel restriction alarm.

 

[clanton]

Re: Whats the root cause of the problem?

Search this site for service bulletins. If dealer installed waterpump, he should have checked the bulletins. Some of the bulletins are 2221 temp sensor, sensor pig tail should be tan with blue stripe. 2225 thermostat seat pn of new seat 336416. Thermostat changed, the correct one is black in color. 2676R1 relocation of tattle tale nipple on block and removal of tattle tale restriction. Impeller change from 3 blade to 6 blade.

 

[Joe Fisherman]

Re: Whats the root cause of the problem?

I ran the motor today without the t stat in and I had no problems whatsoever at 100% throttle.It seems to me for some reason the stat is not allowing the water to circulate threw the head properly.I bought the stat from the johnny dealear here in town for my year and hp motor.What do think is my problem in the stat???? I rule out the impeller/temp sensors. They are working properly..

 

[kenneths]

Re: Whats the root cause of the problem?

The gaskets that go with the T stat, can be a bugger to put back in correctly. If not installed right, it will not allow the T stat to open correctly. Make sure it's in like the manual states. I have seen these with the gasket UNDER the T stat when installed, and this can cause a restricted flow....Good luck!

 

[clanton]

Re: Whats the root cause of the problem?

If the temp sensor does not have a 7 inch pig tail tan with blue stripe, it has wrong temp range to set the alarm.

 

[Joe Fisherman]

Re: Whats the root cause of the problem?

Thanks for your help Clanton is there any difference I have a plain 7inch light brown wire coming from the temp sensor on top of head.

 

[Joe Fisherman]

Re: Whats the root cause of the problem?

Bump

 

[clanton]

Re: Whats the root cause of the problem?

The correct waterpump for this engine is 432995, kit contains 2 modifcations, one for relocation of tattle tale nipple in block, one for change of pressure relief valve spring and cover.<br />Service Bulletin 2221, False overheat signal, change of temp sensor pn 584166.<br />Service Bulletin 2225, overheating overcooling, change of thermostat seat pn 336416.<br />Service Bulletin 2276R1 included in waterpump kit pn 432955.<br />Thermostat was changed. New style is black plastic, the taper on end of housing was changed to stop stat from sticking in stat seat.

 

[jegervais]

Re: Whats the root cause of the problem?

The "plain" tan (light-brown) temp switch closes at 203 degrees. The one with the blue stripe closes at 240 degrees.<br /><br />-John