Engine swap, coupler question.

[Beufort]

So, I’m a sucker who bought something he shouldn’t have, please help before my wife kills me! I have a 85 model montego, 5.7 mercruser alpha 1, its just all bad, but the engine is shot, I secured a 88 5.7, gotta figure out which coupler will fit, looks like I will now need one that looks like a triangle, however seems there are different ones to choose from, anybody know, or better yet, has done this? Thanks in advanced!

[Viper]

All the 5.7 apps of that time and later for Alphas used either 18643A5 or 18643A7 depending on the engine serial number. Do you have the serial number for the replacement engine? Is it a Merc marine engine?

[Beufort]

Thanks! No its not a mercury, I am converting a engine originally in a Chevy truck. It gonna be soooo fun! I just got a A6 coming, we shall see, the coupling that was in the now dead engine was just under 4 inches long, guess I will have to take a few risks going down this road.

[Viper]

Will this be a raw water or fresh water cooled application?

[Beufort]

Fresh water, gonna change the freeze plugs anyway.

[km1125]

You couldn't re-use the coupler from the old engine?

[Beufort]

Source of the post You couldn't re-use the coupler from the old engine?

Nah, the engine that came in the boat is a 1985 gm 5.7, it has a wider bolt pattern for the flywheel than the 1988 i will be using, the original used studs sticking out of the crank, the flywheel and coupler just slid right on the studs and 6 nuts held it all together. I was quite saddened when I took it apart, wasn’t expecting a coupler built like that.

[Beufort]

15943346182397057186979948833675.jpg

got my coupler, not sure what part number it actually is, but the dimensions are spot on, hope to get the engine set in this weekend.