Mercruiser 5.7 (1993) Alpha 1 problem with overheating and RPM

uto70

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Aug 25, 2003
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Hello people<br />My name is Luis, I´m from Panama, Rep. of Panama<br />I own a Bayliner Trophy with a single 5.7 Mercruiser with a Alpha one. It has salt water cooling system. Since a time ago, the gas consume have been increasing, it has problem to start and sometimes overheats at cruising speed with the boat at full load.<br />I changed, new sparks plugs and wires, new coil, did a maintenance to the distributor(sensor and rotor), new fuel pump, new impeller and thermostat, clean the elbows and raisers fron rust deposits. It is with good timming (8°)<br />Please advise
 

crazy charlie

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May 22, 2003
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Re: Mercruiser 5.7 (1993) Alpha 1 problem with overheating and RPM

Is it salt water cooled and how old are the manifolds and risers.Did you back flush the power steering cooler?? Charlie
 

uto70

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Aug 25, 2003
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Re: Mercruiser 5.7 (1993) Alpha 1 problem with overheating and RPM

The manifolds and risers are two years old.<br />I did NOT back flush anything yet<br />Just take out the elbow and risers and clean it up from rust deposits and instaled it again, they seens to look pretty good and put new gaskets<br />Thanks<br />Luis
 

fwas

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Aug 13, 2003
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Re: Mercruiser 5.7 (1993) Alpha 1 problem with overheating and RPM

Luis I had a similar problem, did you check your thermostat housing unit, and thermostat? Also what you might want to check is if your fan belt going to your puly on the water pump is fairly tight, i realized on my engine that once the engine idled I began to notice my temp. rise and fall, removing the engine cover while crusing, then look at the fan belt from the front of the engine, they(fan belt) should not any up and down play between the pullies, at most they should have 1/2 inch of play.
 

metwrench

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Aug 16, 2003
Messages
86
Re: Mercruiser 5.7 (1993) Alpha 1 problem with overheating and RPM

Luis, when you describe the "Starting" problem, Exactly what happens ? Does it seem the Motor LOCKS and then spins freely and starts ?
 

goleft24

Cadet
Joined
Aug 30, 2003
Messages
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Re: Mercruiser 5.7 (1993) Alpha 1 problem with overheating and RPM

Hi Luis, New to this site ,but not these godforsaken motors.Salt water cooled motors are the most difficult motors to determine where the problem can exist because there are so many possibilities.First determine impeller in drive is pumping-sitting at dock with motor running isnt enough.Even a pump that looks and pumps well at idle doesn't mean it's good.Next is Circulating pump on motor.Does your temp gauge move suddenly up and down?Try moving belt pully side to side with your hands. Any movement could mean a pump going bad.Next is Thermostat, Is it correct? Fresh water and raw water cooled thermostats can be different depending on motor. Next is Manifold to exhaust elbow gaskets.If you have "4 risers in between, the gaskets are different.Gaskets with no risers have 2 long slots front and back opposite each other to allow water to flow through with 2- 1/8 inch holes side to side.Gaskets with risers have 4 long slots on each side. MAKE SURE water and exhaust stay seperate, ANY water that makes its way down into the exhaust manifolds due to inside chamber leakage or cross blowing of gaskets,can cause water in cylinders and oil pan causing motor to be hard to start!Check for oil that may look like coffee with cream-NO SUGAR! Hope any of this helps. Mark
 
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