Frequent cause of inboards running hot?

softdown

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Apr 2, 2017
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Other than a bad thermostat?

The previous owner of my S2 quit sailing when the Yanmar 10hp started running hot. Hyacinth are a huge problem in the area. I suspect that plant material got pulled in and clogged stuff up. Is that likely?

May be the heat exchanger? How tough and expensive might that be?

Friend has similar problem with Volvo inboard.....gas motor. So I rushed to the guess that motors may be prone to sucking up junk that clogs the works?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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raw water impeller is number 1 issue
plugged cooling passages from debris is number 2

thermostat is like number 37
 

softdown

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Thanks guys, just ordered a service manual and impeller for my '57 Mercury Mark 55. Am getting into fixing broken outboards, replacing the impeller and lower gear fluid is automatic.

Do I need a 1978 Yanmar service manual? Is the impeller difficult? Good affordable source?
 
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softdown

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Have the main water hose with iron fitting. The left photo also shows calcium deposits in the smaller hole that is a couple inches below the main water hole. Appear to be missing that part.

Yanmar 2GM 13hp
Engine# 08876
Approx. 600 hours on the San Fransisco Bay.....briny to saltwater.conditions.
 

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softdown

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Does anybody know if the motor posted in the above images is:
1) Missing the entire heat exchanger assembly?
or
2) This motor does not use a heat exchanger assembly?

I emailed the seller yesterday and have not heard back yet. Nervous since not having a heat exchanger assembly = boat anchor.
 

Bondo

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Ayuh,... The 1st picture looks like an exhaust port, not a water port,....

If that's the case, yer lackin' the exhaust manifold,...
 

softdown

Petty Officer 2nd Class
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Apr 2, 2017
Messages
102
Ayuh,... The 1st picture looks like an exhaust port, not a water port,....

If that's the case, yer lackin' the exhaust manifold,...

Think I have it. Pretty sure really. Curious that after the big iron elbow, it turns into a big rubber hose. Would have thought the exhaust would be too hot for the rubber hose.
 

Bondo

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Curious that after the big iron elbow, it turns into a big rubber hose. Would have thought the exhaust would be too hot for the rubber hose.

Ayuh,..... Usually inside the big iron elbow is where the water is injected into the exhaust stream,.....
 
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