Swapping engines...need coupler advice

[ydduit]

I have an 87 OMC 5.0 Litre with a Cobra outdrive. The engine is shot... I have picked up an 84 OMC 5.7 Litre that was backed by an 800 outdrive that I plan on dropping in. Now on to my problem...

The 87 5.0 has a 1 piece main whereas the 5.7 litre uses the older 2 piece main. My existing coupler (from the 5.0 part # 3858437) has the wrong size bolt pattern to match up to the older style crank on the 5.7.

Does anyone make a coupler that will fit my application?

Also, the 5.7 uses a smaller fly wheel and my current starter will not work. Can the starter be modified ( larger spur gear) to work with the smaller fly wheel?

Thanks

 

[Reel Poor]

Re: Swapping engines...need coupler advice

I don't think so. That style drive did not appear on the market until 1986 which is when the crankshaft design was changed by GM also. :%

 

[Bondo]

Re: Swapping engines...need coupler advice

Ayuh,........

Seirra has come out with a Retrofit for the Mercruisers in this Swap,........
But,.......
I find Nothing for the OMCs......... No Surprizes There......

 

[Don S]

Re: Swapping engines...need coupler advice

Why don't you just use a Merc coupler the splines are the same.

 

[ydduit]

Re: Swapping engines...need coupler advice

I have done some more research and think that OMC part #3853962 will fit. It appears that in 1986 there was a period that the Cobra drives were mated to the 2 piece main 305 and 350 engines. These engines had the prefix of KW and KWB and used the coupler that I listed above. later in 86 they made the move to the 1 piece mains and coupler part #3858437 (which I currently have).

I have found that the coupler (#3853962) was also used on 3.0L, 4.3L, and 7.4L models into the early 1990s.

Please tell me if I am off base hear but I think this is the coupler that I need....I just hate to spend the money and time to find out that it is incorrect.

Does anyone have one of these couplers laying around that they could measure the mounting hole pattern on?? I require the 3 5/8" pattern...

Don,

What merc part number should I look for? I was told that the Merc used different pitches on the splines than OMC and it would be a sloppy fit...was I misslead?

Thanks again...

 

[HT32BSX115]

Re: Swapping engines...need coupler advice

Don is right. The splines will probably be the same on a LOT of drives......... The splines on my 454 Bravo are the same as the ones on the Wonderful, high tech, KING Kobra 460 I removed from my Four Winns....and you cannot buy that coupler anywhere! Except on EBAY (used)....in fact there's one there now!



Regards,

Rick

Why don't you just use a Merc coupler the splines are the same.

 

[ydduit]

Re: Swapping engines...need coupler advice

"I have done some more research and think that OMC part #3853962 will fit. It appears that in 1986 there was a period that the Cobra drives were mated to the 2 piece main 305 and 350 engines. These engines had the prefix of KW and KWB and used the coupler that I listed above. "

Good news!!!

I just took receipt of the new coupler #3853962 and it looks like it is going to work in my application. Everything is matching up now.

Thanks!!