Omc overheating

Hildebrand

Petty Officer 2nd Class
Joined
Mar 29, 2016
Messages
129
So, agin I wanted to bring this post back up. If I need to make a new one I will. It was 90 here today in Michigan so we took the boat out. Dropped boat in water and fired it up. Ran boat for a few minutes or so and everything was good. We started to out destination, and everything was still good. Once we were getting close to it the boat started creeping past 160 or so. Once we got to out spot to swim I let it idle and it slowly started dropping. I turned boat off and swam for a bit. Started bait back up and all was good agin, once we stated getting to the channel for the boat dock it's started creeping up agin. I would say 15 minute or so boat ride. We hit the channel at slow speeds and the boat started to cool down agin.
Any ideas ? I did pull the raw water hose at the dock and had good stream of water coming out
 

Hildebrand

Petty Officer 2nd Class
Joined
Mar 29, 2016
Messages
129
I will also add this. We are probably in the channel 3-5 minutes to get out to the lake , and then I would say on plane for 10-15 minutes. It doesn't just get high supper quick it's like a supper slow creep up and it will hit 150 and then just supper slow creep up after that.
My temp gauge is 100 then a white line, 150, white line and 240. It'll get between 150 and the second white line
 
Last edited:

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,798
OK now I am going to advise you to invest in a tool that will help you 100% with cooling issues with marine engines. It is a simple IR temp gun, that you can use to read the temp of the engine, risers and manifolds. So with an OMC engine with a 160 thermostat, in all the years I have run mine this is what normal is:
​Idle speed, 160-165. Running on plane, it will initially drop, down to about 160 or a little lower, due to the greater volume of cooling water. Then after you come off plane to idle, expect the temp go to up, to about 175 or so, due to the fact that the engine is still hot, but the volume of cooling water is less. Next after idling for about 10 min it should drop back down to 160 or so.

​OK now how to take readings:
​to get your engine temp, I have found that the spot that seems to follow the temp gauge most accurately is on the intake manifold right under the thermostat housing. The thermo housing itself, tends to read too cool. So if my dash gauge says, about 160, right in the middle, the intake will read 150 or so. I also like to monitor the temp of the manifolds and risers. At idle they should be about 90* or so, barely warm to the touch. Then after running on plane, they may heat up to about 125-135, but will cool back down to about 100 at idle. If you are getting numbers like this then don't worry, some dash gauges can be hard to interpret. My temp gauge has 160 in the middle so its easy to tell when its normal and easy to tell when its too hot. I say anything above 180* is too hot. Manifolds, anything over 160 or so is too hot.
 

Hildebrand

Petty Officer 2nd Class
Joined
Mar 29, 2016
Messages
129
I know I made this post last year but didn’t wanna make another post.
To me, I still feel like I’m dealing with a slight heat issue. The Marina installed a new impeller last year when they winterized the boat because the cage was spun I think they said and it would prime. Yet agin, here I am dealing with what I think it just on the hot side. If I take to the dock and drop it in and let it run it will hit 160 and stay. With a ir fun the mainifods will hit 105-110 just idleing and never leveling the dock. I can’t monitor the manifolds why driving but when I’m driving 25-28 mph my temp gauge ready 160-170. If I get to the Speeds of 30-34 which 34 is about max for my boat it creeps up to 180ish and when I come off plane the temp gauge creeps to 190 and starts to cool back down to 160.
I have installed a new stat. The rubber boots after the risers don’t look like they ever got to hot because they still look in really good shape. I don’t know if my gauge is just old and doesn’t read right and my ir gun is cheap and doesn’t read the best,just not sure.
I don’t wanna toast a motor if it’s something I need to fix.
I haven’t take the impeller off this year yet. I did today why on the hose pull the raw water line and the water kinda pulsates out of it and it’s not like a steady steam of water. At first I think I had a prime issue bc no water came out of that nipple and I played with my muffs till it came out.

Also, I did notice the big hose from the circulating was hotter than the manifolds for the longest time. It was hot to hot and I can handle the risers. What else can I do or do I need to have the manifolds pulled and checked ?
 

Hildebrand

Petty Officer 2nd Class
Joined
Mar 29, 2016
Messages
129
Just wanted to add this. I took the impeller off just now and it still looks brand new. I just put some sealent on it and reinstalled it
 

Hildebrand

Petty Officer 2nd Class
Joined
Mar 29, 2016
Messages
129
Today I started the boat on the hose and I had no water coming from the exhaust bellow so I jumped into the boat and checked the raw water line and nothing. I could suck water from the impeller but nothing came out till the boat hit about 160 and that’s when the little bleeder nipple on the impeller housing started pushing water out. Is that how it’s suppose to be ?
 
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