5.7 mercruiser 1988 engine runs fine to working temp

spoymenov

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Aug 27, 2013
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Hi, I got a doral citation 88 with a 5.7 mercruiser. Now my problem is that engine works great to when reaches operating temp and then runs like crap. No overheating, carburetor rebuild completely, new plugs ,wires, coil, rotor and cap, good gas. Now me and neighbour thinking might be pickup coil or vacuum leak. Any sugestions? Quick help would be apriciated as long weekend is this weekend
 
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84EdH

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Apr 30, 2011
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Re: 5.7 mercruiser 1988 engine runs fine to working temp

Welcome to IBoats. You'll get best results here with inclusion of your engine serial number and drive serial number. So many diff. 5.7setups etc.

that being said, I would first watch the choke plate to insure full open as the engine went from cold, and running good, to operating temp. and running bad. If choke plate doesn't open fully, then that's the problem. If it does open fully, maybe the mixture is too lean, so that when choke opens, carb setting needs enriched.
 

spoymenov

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

Well I had mechanic rebuild the curb and then fully adjust it to run, I had all 4 barreled open and Reving great until gets to operating temp then runs like crap
 

alldodge

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

Well I had mechanic rebuild the curb and then fully adjust it to run, I had all 4 barreled open and Reving great until gets to operating temp then runs like crap

As 84EdH mentioned we sure.... could..... use ..... a.... serial .... number

Sounding like it's starving for fuel. Does it have a mechanical or electric fuel pump (thinking Mech)?
How did you have all 4 barrels open while reving?
 

Maclin

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

"Runs like crap" is pretty vague. We are not there, your best observations and descriptions of what happens and when is all we can work from.

Look at the spark plugs. They will show if it is too rich or too lean. Too rich and I would suspect the choke is working backwards somehow. Too lean and we are looking at fuel delivery (float level, filters clogged, fuel pump output not in spec, air leaks on suction side, yada yada).

Could also be clogged gas tank venting.

Has the mechanic been out on the boat and witnessed the engine's performance at operating temp? It is one thing to set the carb in the shop, quite another to verify the operation at temp.

Observations: Can you smell raw fuel? Does a lot of smoke come out the exhaust? Have you looked at the carb with the spark arrestor off to verify the choke plate is totally vertical?

Does the engine spit back thru the carb? Does it backfire out the exhaust?


Enquiring minds need to know... :cool:
 

spoymenov

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

Hello to everyone again, I will get serials tonight as I had to go back to city for a few hours and going back to cottage soon.
yeah the mechanic tuned the carb on the boat while running and getting to optimal temp. After it reaches working temp it starts to die out and eventually dies, cannot restart until gets cold again, the interesting part is that when it starts to die if you turn key to crancking it working fine as long as the key is turned but as soon as I let go it starts to die again. This morning I had gone to start her up to check the choke again but it wouldn't start. turns over good but no start have to wait to neighbour to come back to help me get it started again. Yeah all 4 barrels opened when we raved it up and it was sucking all the water in so that's all good. Its been a pain in my ... for the past year. well hope that helps and ill get serials as soon as I can
 
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hivoltg

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

Hello to everyone again, I will get serials tonight as I had to go back to city for a few hours and going back to cottage soon.
yeah the mechanic tuned the carb on the boat while running and getting to optimal temp. After it reaches working temp it starts to die out and eventually dies, cannot restart until gets cold again, the interesting part is that when it starts to die if you turn key to crancking it working fine as long as the key is turned but as soon as I let go it starts to die again. This morning I had gone to start her up to check the choke again but it wouldn't start. turns over good but no start have to wait to neighbour to come back to help me get it started again. Yeah all 4 barrels opened when we raved it up and it was sucking all the water in so that's all good. Its been a pain in my ... for the past year. well hope that helps and ill get serials as soon as I can

When the key is turned to the start/cranking position, the coil is fed 12volts again as it bypasses the resistor circuit. I would check if the coil is correct or bad, the distributor, and ignition grounds.
 
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spoymenov

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

well last year just before winterizing, I changed the cap the rotor and the coil. but my neighbour saying it could be a bad new coil from the start so go get one more which I will do today its not too expensive, also changed the spark plugs and the wiring for spark plugs.
 

Bondo

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

well last year just before winterizing, I changed the cap the rotor and the coil. but my neighbour saying it could be a bad new coil from the start so go get one more which I will do today its not too expensive, also changed the spark plugs and the wiring for spark plugs.

Ayuh,.... Welcome Aboard,.... I suppose that's Ok, if ya like throwin' away money alittle at a time,...

We like to Diagnose the problems, by Testin' things out, insteada just throwin' parts at it,...

That's why all these Questions are bein' asked by the guys,...

Dig out yer toolbox, 'n test light, 'n See what's workin', 'n what Ain't,....
 

spoymenov

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

ok I got some serials from my neighbour he said the block serial is not readable but I got the drive and the transom
drive is oc341741 and transom - is oc423473
hope that helps
it said on engine mcm 5.7 350 that's the best I can do unless I go there and maybe find the engraving on block for serial
 

alldodge

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Re: 5.7 mercruiser 1988 engine runs fine to working temp

After it reaches working temp it starts to die out and eventually dies, cannot restart until gets cold again, the interesting part is that when it starts to die if you turn key to crancking it working fine as long as the key is turned

Yeah all 4 barrels opened when we raved it up and it was sucking all the water in so that's all good.

As hivoltg mentioned, when the engine starts to die, you can engage the starter and it will continue to run?? Or did we miss something?

What is this all 4 barrels are open sucking WATER

maybe find the engraving on block for serial

You should be able to find the S/N on the starboard side above the starter

Next time it dies run through this troubleshooting section and let us know what you find.
TB4 troubleshooting.jpg
 
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