mercruiser 4.3 1999

[highrollerskip]

always had a problem since I bought this boat with it dieseling when turning it off while it was hot from cruising but would shut off after letting it cool down the timing is dead on merc specs. has 182 psi in all cylinders. Any help appreciated. Thanks!

 

[Master mechanic]

Carbon on the top of the cylinders. Letting the motor idle for 3-4 minutes before shutting down might solve the problem.

 

[guyjg]

Remove the carbon w/Merc's product or Seafoam. Step the octane up a grade until it stops.

 

[highrollerskip]

Remove the carbon w/Merc's product or Seafoam. Step the octane up a grade until it stops.

Will try that. Thanks

 

[bondo]

Remove the carbon w/Merc's product or Seafoam. Step the octane up a grade until it stops.

Ayuh,.... Runnin' the motor at hi-idle, say 1500 rpms, 'n pourin' a soda bottle of plain ole Water down the carb slowly does the same exact thing,...

It leaves the pistons, 'n heads, Spotless....

 

[highrollerskip]

I used sea foam and octane boost and it solved the problem. Thanks for your help.

 

[guyjg]

I used sea foam and octane boost...

Octane booster is a lousy product...it will foul the spark plugs w/a red carbon ash very quickley...been there and done that.

 

[highrollerskip]

Octane booster is a lousy product...it will foul the spark plugs w/a red carbon ash very quickley...been there and done that.

didn't think I had a choice knowing that I had 70 gal. regular gas already in tank will use middle grade on future fill ups

 

[guyjg]

Well, if it starts to run rough check the spark plugs. Next time you need the octane increased get 5 gallons of Racing or aircraft gasoline...100 octane will rejuvenate old fuel just don't use it straight.

 

[highrollerskip]

Well, if it starts to run rough check the spark plugs. Next time you need the octane increased get 5 gallons of Racing or aircraft gasoline...100 octane will rejuvenate old fuel just don't use it straight.

Do you know what the cylinder compression psi should be on the 4.3 mercruiser?

 

[bondo]

Do you know what the cylinder compression psi should be on the 4.3 mercruiser?

Ayuh,... Over 100 psi, 'n under 200 psi, within 15 psi, from highest, to lowest...

 

[highrollerskip]

How do you know when to change manifolds and risers 4.3 1999 mercruiser