mercruiser 140 3.0 starting and running motor on the ground

[Goldie627]

Hello all, im almost certain ill be taking out my engine for timing gears and possibly rear main seal. I currently have a manifold vacuum of 14. after the gear replacement i would like to start and run the motor on the ground before i put the motor back in the boat. that way i can compare my vacuum readings before and after the new gears as im hoping that the new gears will solve the late timing issue and increase the vacuum preasure

any and all tips for running the engine outside of the boat are welcome

thank you!

 

[alldodge]

Some kind of blocks to hold motor at rear and front motor mounts. Connect a water hose and battery, fire it up. Don't go crazy reving it and it will sit there. You could use blocks of wood and use carriage bolts at motor mount points to hold it tighter

 

[Goldie627]

thanks alldodge!

right now my intake manifold vacuum is 14, and my timing is 8btdc

before I take the motor out i want to advance the timing to the green area on my vacuum gauge, however, this will raise the rpms significantly and push my timing way out so it's not readable with my timing light

my question is is it ok to time the motor by vacuum gauge and ignore the mark on the pulley? I'm thinking the challenge will be keeping the timing in the green while adjusting the carb down to an acceptable rpm

any input is appreciated

 

[Scott Danforth]

my question is is it ok to time the motor by vacuum gauge and ignore the mark on the pulley?

NO. that is a good way to cause detonation and burn up your motor

 

[Goldie627]

thank you Scott! is there a limit on how high you can advance safely? or just don't do that at all?

my 140 3.0 calls for 6btdc in the manual, but the motor seems much more happy at 8btdc

is it possible that my timing mark is off? or is it unlikely?

 

[alldodge]

You could get away with it but if you don't your rebuilding the motor, Just don't do it at all.

To find out if your timing mark has moved, either use a piston stop bolt or since your going to look at your timing gears, it can be verified then

 

[Scott Danforth]

Base timing of 6 degrees or 8 degrees is fine. Total timing of 28 degrees at 3000 rpm.

More than that you will detonate.

As AllDodge indicated, use a piston stop tool, verify that the outer damper ring has not moved