2.5/3.0 early late flywheel identification

Still trying to piece together a "whole motor" have an interest in a rebuilt not yet installed motor. Even used brass core plugs. Still trying to determine if it is a 2.5 or a 3.0 and early or late vintage. Not much to go on as there are NO other parts lying around except an oil pan in OMC blue. My thoughts were with the change to the later style flywheel/crank flange it should be able to be answered there.

What am I looking for? Diameter? number of bolt holes? offset or symmetrical hole patterns? how do you identify a 2-piece rear main from a one piece? Additionally do all these series of engines have timing GEARS as opposed a to a timing chain? The Mercruiser (factory) manual has both shown in places and is this a way to determine vintage?

Thanks again for your help!! It will run again, it will run again, it will run again.....

Re: 2.5/3.0 early late flywheel identification

Ayuh,.....

If you can See the block, it's Quite Obvious whether it's got a 1 piece or 2 piece rear main seal......

And,...
The 2.5l has Only a pulley on the front of the crankshaft,+ the 3.0l has both a pulley,+ a Harmonic Balancer.....

Re: 2.5/3.0 early late flywheel identification

If I understand then the rear main on the later design is visible. Is it pressed into a plate? Have seen many import designs with a similar method. Or is it pressed into the block itself? (with a carrier or bracket to support the lower portion)

Is the cam drive via gears on all these engines?

Thanks again!!

Re: 2.5/3.0 early late flywheel identification

Missed part of the comments.. At this time it is a bare block w/head installed and no pulleys, flywheel, valve cover, rockers or push rods, nothing else to help identify. Thanks

Re: 2.5/3.0 early late flywheel identification

......

Re: 2.5/3.0 early late flywheel identification

Thanks more pieces of the puzzle. The manifold that is claimed to have been on it has a date stamped in the casting of june something 94 and this really confused the issue. Still waiting to find out about the earlier questions. Maybe after I make the 60 miles and look at it again it will be apparent. Thanks

Re: 2.5/3.0 early late flywheel identification

......

Re: 2.5/3.0 early late flywheel identification

curiouser and curiouser... May be that OMC used casting ID that was in 6-xx-94 format. It was apparently not a date as it appeared. Not having the complete OMC history memorized down to the dates it would certainly have appeared to be a date to most I am sure. That's why I come here, to seek out the experts to help with the misunderstood.

Re: 2.5/3.0 early late flywheel identification

Is the cam drive via gears on all these engines?

Click to expand...

Ayuh,...... In-lines are gear driven,+ the V-motors are chain driven.....

If the little motors followed the bigger motors,....
When the rear seal changed,.. the crankshaft bolt pattern for the flywheel went from 3, 1/4" to 3"....