Swapping 2.5 mercruiser

[Jeremygr27]

Hey all im new to this site and on my first boat. Somewhat of a project which i dont mind at all. Anyhow i have a 1987 16ft open bow boat i got for free with a cracked block. Father in law has what he says is a 1976 2.5 mercruiser engine tho i believe it may be even earlier than that. Serial number on block is 3284367 which i cannot find any info on. Ive been gathering info for the last 2 months on as much as i can. I have all the components from my old engine and i am just wondering what things will need to be swapped to drop this older but running engine in. So far the bellhousing was different and wire harness is different number of pins and maybe possibly haveto switch exhaust manifold and riser. Any help or thoughts would be much appreciated. I dont mind a little work and doing projects. Just want to make sure i do everything correctly the first time. Also the engine coupler on cracked engine is a triangle shape bolted on the flywheel. Wondering if i should swap flywheels as well. I have the alpha one gen one stern drive outdrive. I somehow cannot get any pics to upload at this time

 

[Bondo]

Ayuh,..... Welcome Aboard,...... Ideally, you'd strip both motors down to the Long Block configuration, 'n put the older runnin' motor together with all the marine dressin's from the motor that came outa the boat,....

 

[alldodge]

I somehow cannot get any pics to upload at this time

Howdy

You have to post three times before you can upload

 

[Jeremygr27]

Ok great! Thats kinda the route i was going to take. Great to know i was thinking on the right track but i always want to double and triple check everything to make sure. I hate having to do things more than once! Thanks for the fast replies..much appreciated

 

[smiles16]

Just out of curiosity, what type of engine came with the boat? If its a 2.5/3.0 I4, all external bolt on's should be the same. I would assume the flywheels should interchange seeing as both engine use the same model of starter. I don't know much about the models before Alpha One, but Alpha One models should have the same bell housing. Mercruiser used 3 different types of manifolds between the 2.5 and 3.0 from the 70's into the 80's. On the mid to late 80's models, the manifolds were the same on the 2.5 and the 3.0.

 

[Jeremygr27]

I actually just went to swap flywheels and they aren't interchangeable. The flywheel on the broken motor has the triangle coupler plate that bolts onto the flywheel. The running older motor just has the round coupler that bolts on the flywheel bolts. The triangle coupler plate would not fit due to the bolts being too long the triangle coupler plate would not be flush onto the flywheel. So just going to leave the flywheel as it and hope that will not make a difference

 

[Bondo]

The running older motor just has the round coupler that bolts on the flywheel bolts. The triangle coupler plate would not fit due to the bolts being too long the triangle coupler plate would not be flush onto the flywheel.

Ayuh,.... Swap the studs that hold on the flywheel with the shorter studs from the other motor,....

I believe doin' it yer way, moves the splines, 'bout an inch, fore/ aft, in relation to the drive,.....