Need a Genius for this Overheat Problem

[bmdeangelis]

1998 90hp inshore series. At idle for too long, the engine overheats, alarm goes on, engine goes into protection mode. If running at high speed, will last a while longer, but still eventually gets too hot. I think the pistons are staying cool enough to not overheat the engine, but I think the head cover is getting too hot, therefore setting the switch off. I have a thermostat to the head cover, and goes well past 175F when it gets hot. (Also, I have removed the switch so it just hangs in the air so engine does not shut off, and run the engine hard.....head cover gets way too hot But no seizing.....again I think pistons are staying cool enough but head cover gets too hot)

I have put a new pump in. I have put a new thermostat, pressure spring, and thermo switch. I took the head cover, head and exhaust plates off. Cleaned out all deposits and looked for blockages. NOTHING!!!!! I have no idea what else I could possibly check.

Nobody can solve this problem. Can you??

 

[cjrama]

Re: Need a Genius for this Overheat Problem

try taking off lower unit. then pull thermostat covers and thermos out. put hose directly in covers and flush hard. possible blockage may be flushed down. also then try putting hose up water intake from lower nit and run motor. if it does not overheat you know that you are not getting enough flow fromwater pump. also make sure water pump is tight good impellar spin and no leaks . if water pump is leaking it is not shooting enough h2o to motor.

 

[wvmedic]

Re: Need a Genius for this Overheat Problem

bmdeangelis, check out these two links. The first one shows my top piston the damage is from what I believe to be from heat, and if you pulled you're sensor out and continue to run like that you are going to ruin that motor.

The second link shows what I removed from the water pickup tube, the debris were at the top of the tube just under the base plate.


http://forums.iboats.com/showthread.php?t=317158

http://forums.iboats.com/showthread.php?t=314405

Jeff.

 

[bmdeangelis]

Re: Need a Genius for this Overheat Problem

Thanks for the suggestions, guys. I will try next. Jeff - thanks for the advice, but I know I am not overheating pistons. I just had my head off and pistons looked great (nothing like yours). This of course, is not to see that won't happen if I don't fix my problem.......which is why I need to solve.


Would it be possible that I am getting water through but not enough water...i.e. a partial blockage? How do I know if enough water is coming through?

 

[wvmedic]

Re: Need a Genius for this Overheat Problem

bmdeangelis, try cjrama?s suggestion.

Yes it is absolutely possible for the motor to have flow and not be enough.
The motor pictured was peeing great, but it wasn?t enough to cool it as it should. I didn?t know that the piston was like that till I took the exhaust cover off and it was staring me in the face, I rotated the crank to check the others and there was no damage to the others. Just a side note when I took the head off there was no damage to the cylinder or the piston either, not till I took the exhaust cover off did I find the damage. I probably wouldn?t have found it then if it wasn?t in the position you see in the pictures.

Jeff.

 

[wvmedic]

Re: Need a Genius for this Overheat Problem

bmdeangelis, from what I can tell with my motor and other posters here. The only sure fire way to monitor if you are getting enough flow is to use a water pressure gage.

Jeff.

 

[bmdeangelis]

Re: Need a Genius for this Overheat Problem

Thanks for your time Jeff. I took the lower unit off...running water directly up the intake.....engine barely got hot. Must be not getting enough water from the pump. I removed the tstat and blew water down, hoping pressure will blow out any clogs.

If there is a clog between the pump and the head......then I have no idea how to get at it.

 

[wvmedic]

Re: Need a Genius for this Overheat Problem

bmdeangelis, if it is a mud dauber nest or the like, you can probably take the lower unit off and use a metal close hanger to run up the tube from the bottom and get it out.
But in my case I bought the motor used and the previous owner let the impeller go till it came apart and got sucked up the tube, then someone just put a new impeller in and didn?t get the old pieces out.
In that case the powerhead and probably the lower unit will need to be taken off to get to the water pickup tube.

http://forums.iboats.com/showthread.php?t=326649

Jeff.

 

[bmdeangelis]

Re: Need a Genius for this Overheat Problem

Well, I think I found the problem. That's the good news. I took apart water pump again. Although I have replaced the 'water pump kit', I never really paid attention to the water pump base. The 3/4" piece of steel that the entire thing is housed on. Well, mine was corroding and in bad shape. I think that's why my water source was not enough......

....now for the bad news. In trying to get the thing off, the 'collar' of the base that extends into and along the shaft got completely corroded in place. In other words, I got most of the base off, but there is quite a bit of steel left behind on top of the bearings. If I can't get it out (which looks likely), my only other option is a new lower unit.

 

[wvmedic]

Re: Need a Genius for this Overheat Problem

Well I?m glad you figured out the problem, but am equally sorry to hear about the other problem.

Let us know how it turns out.

Jeff.