mercruiser 5.7 coupler swap

[rick332]

i am switching engines from a mercruiser1983 350 to a omc 1988 305 the rear crank pattern and coupler are different .is there acoupler for the 305 that will replace my 83 merc.coupler so i can use my merc. bellhousing? i think and have been told everything else willwork if i swap merc. parts to the omc engine. please advise me if i will need other parts for this swap. thanks ,and if anyone knows the best type or place to get the partsi need.thanks again.

 

[Bondo]

Re: mercruiser 5.7 coupler swap

Life will be Much Easier if you just use a Pre-1986 SBC Engine...........

 

[anesthes]

Re: mercruiser 5.7 coupler swap

Spend $100.00 on a crank adapter, and run a old style crank. <br /><br />Drag racers have been going 10 seconds and faster on these setups, so they'll work in your boat. <br /><br />-- Joe

 

[rick332]

Re: mercruiser 5.7 coupler swap

What do you mean by old crank?

 

[rick332]

Re: mercruiser 5.7 coupler swap

What do you mean by old style crank?I wanna run the crank thats in the 5.0 omc 1988 model engine.It is complete ready to go.

 

[Bondo]

Re: mercruiser 5.7 coupler swap

is there acoupler for the 305 that will replace my 83 merc.coupler so i can use my merc. bellhousing?

The Short Answer is....... Maybe.........<br /><br />You can Try an Alpha Coupler, <br />But you Might find the Length is Different...<br />The Mod.1 was Never Built since Chevy went to the Small Crankshaft Pattern......<br />You also Could have a Problem with Flywheel Diameters....... Some thing to Check on......<br />I'm not Sure if the Bravo Coupler is Shorter, or Longer than the Alpha Coupler.......<br /><br />I Still Say,<br />

Life will be Much Easier if you just use a Pre-1986 SBC Engine...........

And, A 350cid at That........<br />Who wants to go Down in Power..??....

 

[rick332]

Re: mercruiser 5.7 coupler swap

ok bondo try to give me something factual or no grease at all... maybe you need more info. <br />i already have both complete engines,that means flywheels starters everything!power isnt the issue either my question was i am installing a 1988 5.0 omc where a1983 5.7 merc. was removed from the bolt pattern on the rear of the crank are obviously different as are the couplers and housings i can see i will have to use the merc housing for mountings to line up it looks like ican use the 88flywheel and starter the couplerseems to be the problem the 83is the smaller round one thatconnects directly to the back of flywheel. the 88coupler is much larger and wont fit through opening in 83 housing is there one shaped like the 83 that will bolt to the 88 crank?

 

[anesthes]

Re: mercruiser 5.7 coupler swap

55-86/87 uses a 2 peice rear crank.<br />88+ uses a 1 peice rear crank. They are different.<br /><br />My suggestion was, use the crank from the '83 and an adapter so you can reuse your old coupler.<br /><br />-- Joe

 

[rodbolt]

Re: mercruiser 5.7 coupler swap

yes there is a coupler<br /> its the large triangle shaped one that mounts to the flywheel where a clutch pressure plate would have been. its a fairly simple swap we repower with one piece seals all the time.<br /> good luck and keep posting

 

[rodbolt]

Re: mercruiser 5.7 coupler swap

a quick ps<br /> in 1985 GM went to the center bolt valve covers and one piece seals on the rear main on the sbc. if your covers are center bolt and the heads actually came with the block its a one piece rear main. merc foresaw the engine update problem and made couplers accordingly<br /> its way to much trouble to swap cranks.<br /> good luck and keep posting

 

[Trent]

Re: mercruiser 5.7 coupler swap

Couplers