Mercruiser 3.0L 140 hp alpha 1 running temperature

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Cold whack

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Can any tell me what the running temp should be on this motor(1991 Mercruiser 3.0L 140 hp alpha 1). It has a 140 degree t stat which I have replaced, also replaced impeller and housing. Today I will remove elbow and inspect for any clogs. When I run it on muffs it runs about 150 when I took it on maiden voyage it got up to around 185 so I shut it off let it cool and put it on trailor. Bought ths boat from a guy who let it sit for 3 years. When I got it home it wouldnt turn over So I replaced ignition, changed oil and filter , new fuel filter, flushed old gas, rebuilt carb, new t stat, new water pump/impeller. So again I am not sure what safe running temp should be.
 
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ENSIGN

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Welcome to iboats!185 degrees seems a little high,I would run the boat again and verify the temp with a infared temp gun to make sure the gauge is reading correctly.
 
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Cold whack

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

This is the flapper I removed. Was still in place but not in to good of shape. How important is this can I remove it completely or do I need a new one
 

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Don S

Don S

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

You need a new one. They keep water from sloshing back up the exhaust and into the engine causing a hydrolock.
But that is not your temperature problem.
 
tazrig

tazrig

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Cold whack said:
Can any tell me what the running temp should be on this motor(1991 Mercruiser 3.0L 140 hp alpha 1). It has a 140 degree t stat which I have replaced, also replaced impeller and housing. Today I will remove elbow and inspect for any clogs. When I run it on muffs it runs about 150 when I took it on maiden voyage it got up to around 185 so I shut it off let it cool and put it on trailor. Bought ths boat from a guy who let it sit for 3 years. When I got it home it wouldnt turn over So I replaced ignition, changed oil and filter , new fuel filter, flushed old gas, rebuilt carb, new t stat, new water pump/impeller. So again I am not sure what safe running temp should be.
Click to expand...

If those are the original elbows they are probably due to be replaced. If the boat sat for 3 years and wasn't properly flushed prior to sleep you probably have some rust floating around in your cooling system too. When you replaced the t-stat did the t-stat housing passages look clear? (not all filled up with rust)
 
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Cold whack

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

tazrig said:
If those are the original elbows they are probably due to be replaced. If the boat sat for 3 years and wasn't properly flushed prior to sleep you probably have some rust floating around in your cooling system too. When you replaced the t-stat did the t-stat housing passages look clear? (not all filled up with rust)
Click to expand...

Don't really recall but I do notice rust coming out in the water when I drain the manifold
 
Don S

Don S

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Rust coming out of the manifold drain is normal. Still need to know if you have an Alpha I or an Alpha I gen II as I asked up in reply #3.
 
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Cold whack

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Don S said:
185 is too hot, with a 140? stat, you shouldn't be seeing over 170?.
Do you have an Alpha I or an Alpha I Gen II drive. Being a 91 boat, it could have either. Go to this link http://forums.iboats.com/mercruiser...cellaneous-mercruiser-information-329915.html and scroll down for some pictures if your not sure.
Click to expand...

I'm sorry it is a 90 not a 91 and is alpha one
Thanks for the link although I could not find the correct serial number
SN from my engine is oc761599
 
Don S

Don S

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Now we are getting somewhere. That is actually your engine serial number, and an 89, not a 90. Model # 430B0009S
It is an Alpha I, NOT Gen II.

When you replaced the impeller, did you also replace the gaskets and wear plate? If not, they could suck air when you get on plane and the pump is up out of the water.
 
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Cold whack

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

I removed the whole out drive this past weekend and went over water pump again and there was a gasket under the base plate that I had missed I replaced it as well as the two gaskets over and under wear plate got the flapper replaced and put it back on the lake very pleased to say boat ran all day at about 120 to 145 hottest it ever got was 150 so I thank you guys so much for all your suggestions
Now motor is shaking quite a bit and I noticed a little movement in carb just above the base plate where the gasket is and a little fuel leakage so I guess the guy that rebuilt my carb didn't get it tightened correctly
Do I need to remove entire carb to tighten this section (Rochester 2 barrel) or could it be spark plugs
 
achris

achris

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Cold whack said:
...Do I need to remove entire carb to tighten this section (Rochester 2 barrel) ..
Click to expand...

Yes. And no, spark plugs won't make the carb leak fuel.... But as they are 3 years old and not an expensive item, replace them anyway....

Chris.....
 
Don S

Don S

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Re: Mercruiser 3.0L 140 hp alpha 1 running temperature

Now motor is shaking quite a bit and I noticed a little movement in carb just above the base plate where the gasket is and a little fuel leakage so I guess the guy that rebuilt my carb didn't get it tightened correctly
Do I need to remove entire carb to tighten this section (Rochester 2 barrel) or could it be spark plugs
Click to expand...

Yes, you will need to remove the carb, and since it's that loose and leaking, it may need to have a new gasket installed between the loose parts, and absolutely you must replace the gasket between the carb and manifold.
Your engine could very well need a complete tuneup as well.
 
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