1995 volvo 3.0gs mhub over heating

bossp505

Cadet
Joined
Mar 27, 2011
Messages
7
I got my boat last week. Took it to the lake, did great. I took it back out 2 days later about 15 minutes in, it overheated. i did not know I was not to start the motor without water. I got home looked it up and found the impeller on raw water pump might have burnt up. I connected the water to muffs, pulled off the pump output hose started boat for about 10 seconds (more than enough time for water to flow thru). water did not. I pulled the pump off and sure enough the impeller was burnt up. I replaced the impeller yesterday and did the same test, and the water was flowing with real good pressure. I connected it all back together. I made sure everything was tight and started it, About 10 or 15 minutes in the temp gauge almost hit 200 so i shut i off. I pulled the t-stat, It looked old with a little rust , But i put it in boiling water and it opened right up... I put everything back and tried it again and same problem.


I forgot to mention i pulled all hoses except to the circulating water pump to clear out rubber impeller parts... also when the motor overheated, I think its called the exhaust bellow. it was smoking lightly with a burnt rubber smell.

I just wanted to see if theres something else i should look at other than clogged hoses, and t-stat . i know the bellow has flappers, Could they some how melt shut causing water not to flow out. Also there is no water flowing out the prop from what i was told thats where the water and exhaust come out... There IS water flowing out the bottom of sterndrive
 

fcawth

Seaman Apprentice
Joined
Feb 16, 2009
Messages
44
Re: 1995 volvo 3.0gs mhub over heating

Be sure to search for impeller bits everywhere you can. There may be other damage from running dry, but those impeller bits can get everywhere. For one, take off the socket head screw on the thermostat housing at the top (using an allen wrench) and look at the small bypass hole inside. There may be an impeller bit in there. When I bought my 3.0 volvo gs, there were impeller bits (lots) in the hose going to the thermostat housing from the raw water pump(from previous impellers), in the hole I mentioned above, and even in the engine itself in the small passages going down to the block from the head (just found these when I took the head off to do a valve job).

Mine didn't overheat even with some impeller bits in there, so you may have more of an issue.

Others on this forum can give more information about other possibilities (i.e. exhaust flapper (definitely can melt), circulating pump, etc.)

No (or maybe very little) water comes out the prop hub normally when running the volvo on muffs. It comes out other places (there is a plate on the transom shield that may or may not be there so it could come out there or from the other exhaust passages on the drive)

Also make sure that you have the hoses on the raw water pump in the correct order.

I guess they risk something else getting plugged up, but it sure would be nice if there was a screen or something that prevented these bits from going all over the place..
 

bossp505

Cadet
Joined
Mar 27, 2011
Messages
7
Re: 1995 volvo 3.0gs mhub over heating

Thanks for the reply! I think i found the problem today. it was a clogged exhaust riser with liquid gasket in the water port. i ran it for 20 minutes after with the temp never going over around 150. im not sure if thats normal being that the normal running temp is 170?
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 1995 volvo 3.0gs mhub over heating

This is why when you have an overheating problem, you put all the information about the overheating in a single post instead of a seperate post on each item in your cooling system.
This post explains why your engine is running at 150? instead of 170?. Probably a piece of old impeller partially holding the stat open.

Might want to go to the link below and download a owners manual and give it a read. Might find something else you are doing that you shouldn't be. You do lower the drive before starting don't you ???????
http://www.volvopenta.com/volvopent...lication_search/pages/publication_search.aspx
 
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