4.3 mercrusier

1

1452pf

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Jun 20, 2011
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What is the normal operating temp of this engine. After a extended trolling with this 4.3 it seem to be foulded out, takes a period of time to operate correctly. It sputters, coughs, has no power, if I stop, set in neutral rev it, then it will under power resume to run correctly. Is there a hotter plug to kept from fouling out?
 
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badcarma58

Seaman Apprentice
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Nov 15, 2010
Messages
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Re: 4.3 mercrusier

I was told to use a 165 degree thermostat if you troll alot. If using the 165, don't use WOT for very long periods though.

The normal operating temp is 143 for freshwater applications.

I have twin 4.3 engines, and was being told various temps depending on what manual I was looking at. I logged onto here and got the scoop on 143 vs. 165.
 
Don S

Don S

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Aug 31, 2004
Messages
62,321
Re: 4.3 mercrusier

Does your 4.3 have a year or better yet a serial number since year doesn't really mean much on boats.

Sounds to me like you have carb problems, not temperature problems.
When was the last full tuneup? With compression test? Have you replaced fuel filters lately? Is the choke working and adjusted correctly? Idle mixture adjusted for your engine?
 
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1452pf

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Joined
Jun 20, 2011
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Re: 4.3 mercrusier

Don S said:
Does your 4.3 have a year or better yet a serial number since year doesn't really mean much on boats.

Sounds to me like you have carb problems, not temperature problems.
When was the last full tuneup? With compression test? Have you replaced fuel filters lately? Is the choke working and adjusted correctly? Idle mixture adjusted for your engine?
Click to expand...

The engine is from 1990 bayliner, it starts fine runs great, except after trolling, its seems to be fouled out, applying throttle it sputters, hesitates, coughs, in idle and neutral its OK, once its revs up, then it will have power to get on on plane. The only thing I noticed is that the water temp never goes over 125-130 degrees.
 
1

1452pf

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Joined
Jun 20, 2011
Messages
3
Re: 4.3 mercrusier

badcarma58 said:
I was told to use a 165 degree thermostat if you troll alot. If using the 165, don't use WOT for very long periods though.

The normal operating temp is 143 for freshwater applications.

I have twin 4.3 engines, and was being told various temps depending on what manual I was looking at. I logged onto here and got the scoop on 143 vs. 165.
Click to expand...

Thanks for the information, what doy you mean by WOT for long periods.
 
Don S

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: 4.3 mercrusier

The thermostat for the 4.3 is a 143? stat, but that is not the normal operating temp.
At idle in gear, there is no load on the engine, and with all that cold water, it may not get up to temp. When you get on plane, you should be seeing around 170? on your temp gauge. Even if you change to a 160? stat, it will still run in the 170? range and will not hurt anything, even at WOT (Wide Open Throttle). The lower temp stat is mostly there incase the engine is used in salt or brackish water. If in fresh water, no problems using the 160? stat.
If it's loading up, you still need to adjust the carb mixture and tune the engine up and make sure the choke is fully open.
 
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