Engine overheating at trolling speed

hz293

Seaman Apprentice
Joined
Jul 27, 2015
Messages
46
5.0 heats up when at lowest troll

heat shows great when I'm moving except when it is at its lowest. As soon as I speed up a little it's great. Just got the boat and want to troll for Kokanee using my happy troller plate but need to fix it first. Does this sound like an impeller problem?
 
Joined
Mar 27, 2010
Messages
3,008
Welcome HZ.... .

What Year?

What Drive?

When was the last time the impeller was changed?

We don't need to know what the size of the boat... or the boat manufacture... the engine specs are what we need....
 

Rick Stephens

Admiral
Joined
Aug 13, 2013
Messages
6,118
I'm also a kokanee addict. I tried a happy troller just a couple times and ended up adding a small outboard and dumping the plate. It's hard to keep speeds down enough even with a plate.

The '84 Honda 4 stroke 10HP outboard runs all day on a couple gallons, nearly silent, and gives me backup power just in case (especially nice when I want to head over to the coast and run on the big water) If I went a later model outboard I'd have to get something smaller, 6-8 hp, to still be able to keep the speed .8 mph or lower. Newer 'high output' motors will push you along faster with a smaller engine.

If you do a lot of kokes you're going to want a trolling motor, electric or gas. Running that big engine is not nearly as good.

Rick
 

hz293

Seaman Apprentice
Joined
Jul 27, 2015
Messages
46
Thank for the feedback. Boat is a 1989 Chaperral 198xl with 5.0 merc and alpha 1.
 

hz293

Seaman Apprentice
Joined
Jul 27, 2015
Messages
46
Btw, don't know when impeller was changed. Just got it. I'll go ahead and change it to make sure.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,464
Btw, don't know when impeller was changed. Just got it. I'll go ahead and change it to make sure.

Ayuh,..... Welcome Aboard,.... Great place to start,....

Also, make sure the check-balls are free in the t-stat housin',....
They're in the nipples goin' to the exhaust risers,...
 

hz293

Seaman Apprentice
Joined
Jul 27, 2015
Messages
46
5.0 Mercruiser with alpha 1. Proper temperature when moving but when throttled down it goes almost to 240. This is a seawater cooled. Will replacing the thermostat fix this problem or are there other things I should look at?
 
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