1990 Mariner 40hp very high compression?

[deejaycee_2000]

I recently replaced the block on my 40hp mariner and did everything exactly to the book on replacing the block with all the gaskets etc. I now find that is very very hard to pull the engine with the start rope (i have no electric starter). It is as if the compression is really really high now, the pistons and rings where in very good condition so I didn't replace them, I replaced the block because it was repaired previously but the welding didn't seal properly, and the pistons is the standard size pistons not oversized. Why could this be, and what should I do about this? Any suggestions would be appreciated ...

 

[Moody Blue]

Re: 1990 Mariner 40hp very high compression?

I doubt the compression is so high you are having trouble pull starting it. I'm no professional but it sounds to me more like a mechanical clearance/friction issue. Try removing the spark plugs and turning the motor over by hand. It should spin freely. Does the motor run?

 

[deejaycee_2000]

Re: 1990 Mariner 40hp very high compression?

Well the motor ran before I replaced the block, but even then it was very hard to pull, even when removing all the plugs it is still hard to pull, there is no friction noise coming from the motor. I can't get the motor to run as of yet cause I damaged on of the air screws on the one carb and I am waiting for parts on it. But it still bothers me why this motor pull so difficult, always has .....

 

[deejaycee_2000]

Re: 1990 Mariner 40hp very high compression?

^

 

[MercFan]

Re: 1990 Mariner 40hp very high compression?

Easiest way to know if it's compression or friction you're feeling is to remove the spark plaugs and then pull it.

 

[Moody Blue]

Re: 1990 Mariner 40hp very high compression?

I would remove the lower unit AND the spark plugs. If the motor does not turn over easily by hand then something is wrong in the powerhead itself. When you rebuilt the powerhead, was everything properly lubed before reassembly?

 

[deejaycee_2000]

Re: 1990 Mariner 40hp very high compression?

Yep, I lubed everything, I rebuilt the powerhead 100% to the book, that's why it it strange for me to think there could be something wrong .... Hey MercFan I see you are from South Africa, where you at?