T stat and gauge question

[carcraze]

Hi all

I have a new used boat I have been going through to get ready to go. 88 Merc 350 mag with alpha drive. I ran both engines on muffs and the left heated up and stabilized the right read cold with no temp rise mind you the motor felt warmed up and so did the water exiting.

Long story short it seemed to be the lack of a grounding gasket under the housing. I tore it down and it was the wrong gasket and the Tstat seems to work fine but in tearing it down it looks like the sleeve is in upside down. The service manual seems to confirm this but thought I would ask the question.

The tab on the sleeve was lined up to the key in the housing but the tab was on the bottom and must have been hammered in, the window cuts in the sleeve did not line up with the hose ports I assume feed the manifolds. Fliping it over puts the tab at the top when lined up with the key and the port windows now line up to the hose ports in the housing is this the correct way it should go in?

Also I have not had it out this way but if it was ran this way what other damage may have incurred, guess I should check the other side as well?


I so hate finding these kinds of mistakes.

 

[jtmarten]

Re: T stat question

Re: T stat question

Grounding gasket??
The gasket for the t-stat housing is a plain gasket. I don't think I even replaced the gasket on either of mine, just used permatex. I had to replace both t-stats and sleeves last year (first year with this boat). The sleeves aren't worth saving/re-using. I'd just replace both sets and have peace of mind. Impellers/WP housings too if you don't know when they were replaced.
Does the temp gauge work? Does it peg if you ground the sending wire?

 

[fossill]

Re: T stat question

Re: T stat question

There is indeed a "grounding gasket', if you want to call it that on some models.
It's there to provide a ground for the temp sensor that sits in the thermo housing on some units. Mine has it too.

 

[jtmarten]

Re: T stat question

Re: T stat question

Interesting. Wouldn't bolting it to the block provide a ground??

 

[fossill]

Re: T stat question

Re: T stat question

Not according to the merc service manual.
Pg 6A-23, manual #25 among others for those who don't believe me.

 

[carcraze]

Re: T stat question

Re: T stat question

SInce the bolts come in from the top of the housing and there is a gasket there as well as a gaslet under the upper housing there is no ground path, so the sensers so not function. This is on the housing with the flow restriction balls as other housings are different. This model has a bottom gasket that has 4 small copper eylets that produce a ground to the upper housing the sensors sit in, even using a gasket cement can render them useless.

My question pertains to the sleeve being upside down though and any other damage maybe to the manifolds?

 

[fossill]

Re: T stat question

Re: T stat question

The service manual shows the proper way to install.
As for any damage being done prior, I don't know.
Not sure if you sea trialed it or not prior to purchase but if there was a problem it would have showed then.

 

[carcraze]

Re: T stat question

Re: T stat question

Or if you want to look at service manual 9 6a-14 where it says if the gasket has continuity rivets do not use perfect seal.

 

[carcraze]

Re: T stat question

Re: T stat question

Yep looked through the service manual and I think I have it correct just wanted to verify as the picture is rough to see. I did not sea trial as it was a local boat that I knew of but now I am sure wishing I had.

Lesson to be learned there for sure, mind you all this started diagnosing a gauge not reading right.

 

[jtmarten]

Re: T stat question

Re: T stat question

Well, potentially then everything was functioning properly as far as cooling, you just may have needed a ground for the sending unit to function.

 

[carcraze]

Re: T stat question

Re: T stat question

Thanks for the help I knew something was up when the gauge checked out and the sender looked new in the housing so I checked the ground VIA an ohm meter. The biggest concern I have now is with this stupid sleeve which appears to be brass, which also appeared to be in upside down if I am reading the blow up in the manual right. When in wrong it blocked the two hose ports in the housing. There was enough wear in the housing they got some water from folw behind the sleeve I think.

My worries now is if the manifolds were running with reduced water to these ports could the manifolds be damaged, that coupled with a gauge screwy just wondering if I should be checking something else before my upcoming first run?

The compression check on that motor was quite good though.

 

[carcraze]

Re: T stat question

Re: T stat question

A quick update in case it can help someone in the future.

The new gasket with the copper rivets along with a housing and block clean up solved the gauge issues. The sleeve was in wrong and now I have good flow to the manifolds and it runs okay, temps look good.

1 manifold does run hotter that the other one but this appears on both engines so I assume it is a non issue as they are not overly hot. May look into new manifolds in the fall as they are probably due to be replaced.

Now on to the next screwed up system in the thing, got to love used boats.

Thanks