Thermostat Housing

[rad1026]

1989 5.7L 260HP Mercruiser. I bought this chaparral last year and it ran great all season. I started it up on the muffs tonight after sitting for the winter and noticed the starboard side exhaust manifold got much hotter than the port side. I removed the hoses coming from the thermostat housing to the exhaust elbows and found these spring loaded balls that sit in the between the housing and seem like they must act as a sort of one way valve. My factory manual does not show anything like this. Does anyone know why they are there? And if they could possibly be why no water seems to be flowing to the starboard exhaust elbow? Thanks for the help.

 

[Bondo]

Re: Thermostat Housing

Ayuh,..... They Are Supposed to be there,.....
And, I'll defer to Don or somebodyelse to explain Why.......

While the starboard-side Shouldn't get Really Hot,....
SBCs water flow patterns Do tend to make the starboard-side run Slightly Warmer than the port-side.......

In other words,....... Your Issue,.... May Not be an Issue at All.......

With the motor Running,....... Are you getting reasonable Water Flow thru those Hoses,..??..??......

 

[rad1026]

Re: Thermostat Housing

The port side yes. When I shut the engine down I pulled the drain plug on the starboard elbow and no water came out at all. I didn't check the manifold, but the hose going to the starboard elbow didn't seem to be flowing at all. Maybe I'm making too big a deal of it but I could put my hand on the port side comfortably. The starboard side was pretty darn hot, I mean it is an engine and when it gets up to 160 degrees I know that's pretty hot to the touch, but there should be some water flow in the elbow and it seems like some water should drain out of it. Does the water settle down in to the manifold after shut down? Is that why I may not see water draining from the elbow. Appreciate your reply.

 

[Bondo]

Re: Thermostat Housing

Does the water settle down in to the manifold after shut down?

Ayuh,...... Atleast as far as the Lowest Outlet......

Try it with the engine Running,+See if there's Flow.......
Pull the Hose to the Riser/ Manifold I mean.....

 

[Don S]

Re: Thermostat Housing

The poppet valves controls the amount of flow going to the elbows. They do need to be there.
That being said, pull the starboad hose off the Riser and start the engine and see if water comes out of the hose. It may very well be the manifolds and risers are old and plugged with rust.
How about your raw water pump impeller? How old is it?

 

[rad1026]

Re: Thermostat Housing

replaced the raw water impeller last season when I purchased the boat. I will pull the hose off and start the engine and see what I find. In the mean time I have my outdrive off to grease the splines and there is water in my large bellow. I probably have a leak don't I? I hear they are a real PITA. Talk to me experts, I want to be able to do this myself. The boat is 1989, who knows when they were done last. I don't have the money to pay someone. I'm very mechanically inclined. Is there a chance water just settled in there when I pulled my outdrive back?

 

[Don S]

Re: Thermostat Housing

Is there a chance water just settled in there when I pulled my outdrive back?

Nope, you have a leak.

Here is a link to section 4A of the OEM service manual that covers changing the bellows.
http://www.boatfix.com/merc/Servmanl/6/6A4R3.PDF

Here is a link to the complete service manual for your drive.
http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf

Click here for a site with the bellows info sorted out for you.

 

[rad1026]

Re: Thermostat Housing

I know I can rent the tools from a local repair shop. Thanks for all the info. I'll let you know how it goes. I'll probably be back with questions. I won't get in to it until next weekend. How many people tackle this job, and what level of ability is necessary?

 

[Don S]

Re: Thermostat Housing

There have been lots of guys here that have changed those bellows before. There is nothing technically difficult about the job, it's just a real PITA to do.
It takes me about an hour and a half to change one, but I do at least a dozen or more per year. First timers usually spend a weekend doing the job with frequent stops for bandaids and a cold drink and negative comments about everything on the back of the boat and in the boat, boats in general, and boat designers and engineers specifically.
Just take your time, and don't let it get the best of you.

 

[rad1026]

Re: Thermostat Housing

I appreciate the pat on the back. I know what you are saying from years of wrenching, so as far as the patience goes I'll do fine. I have the factory manual and was reviewing it tonight. It really doesn't look too difficult. I'm sure there are little tricks of the trade that come with experience, but you have to do it the first time to get the experience. Wish me luck. Thanks again.