engine manual

Hello. i am new here and am a rookie to boating and such. I just bought a 1979 cruiser beachcomber with a 305 mercruiser. and the guy said that the motor was a 305. It says "gm" in a couple places on the engine. i can not find the serial number anywhere on the engine. I found a number on top in front of the distributor - "6269797 GM 13". I am just stumped on where the serial number would be/is. Im thinking that the engine is not original. any help would be appreciated! thanks!!

Joe, the ignition distributor number will not help you.

If the engine is a 1979 vintage, the numbers will be here. These were OEM with perimeter bolt valve covers.




If the engine is post 1986, the numbers will be here. These were OEM with center bolt valve covers.
Note the 5.0 in the casting. This block is a 5.0L or 305 cu in.





Your cylinder head casting numbers will reveal themselves with the valve covers removed.
These numbers will give you info on combustion chamber volume, light -vs- heavy casting, year range, etc.
(example only)





What is it that you are wanting to know regarding the engine block number?
Perhaps you don't actually need this information.



.

ok thanks for the information! I want to get a service manual for it, and would also like just to know what year etc. the engine is.

Joe, unless you are seeing non-OEM components on this engine, a manual for your year model will most likely serve your needs.

The 5.0L and 5.7L engines share the same stroke dimension.
The engine foot print is identical between the two.
Your ignition timing specs will be very similar if not the same.
Either can use the same ignition system.
Any maintenance will also be very similar if not the same.
Starter motor is determined by the flywheel ring gear tooth count.
Exhaust manifolds will be same for either.
Engine circulating pumps are same for either.


.