omc engine coupler

[m2hunt]

help on my 1990 3.0 140hp i found a short block but it is a older block with a 2 pc rear seal what i need to know is witch engine coupler do i use merc or omc for the cobra outdrive when i had the 1990 running i felt a viberation when i took the motor out i saw why the rubber in the coupler was bad can u help
thanks mark

 

[Don S]

Re: omc engine coupler

If your outdrive is an OMC, get an OMC coupler. IF it's a Merc outdrive, get a Merc coupler.
While the splines may be the same and the bolt pattern for the crankshaft, as I recall, the OMC coupler was longer

 

[m2hunt]

Re: omc engine coupler

what about the diff in the years the old motor has a 1 pc seal and the new motor i just got has a 2 pc seal does that matter

 

[Don S]

Re: omc engine coupler

You need a 983902 OMC coupler for your older engine. The newer engine with the one piece rear seal takes a 986917 coupler.

 

[m2hunt]

Re: omc engine coupler

thanks for your help is the fylwheel diff too since this bolts to it

 

[Don S]

Re: omc engine coupler

Go to the link below and compare part numbers, the 87 had the 2 part rear main seal, and the 90 has the single piece. IF the part numbers are different, the parts are different.

http://12.2.215.22/pub/default.asp?SessionId=79ffdcc7e0474510b258198ab44956dc&Lang=EN&brands=EJ

 

[m2hunt]

Re: omc engine coupler

may i ask how u got the part number i looked on the sight u gave me and it shows 73-76 140 is 982511 for the coupler

 

[Bondo]

Re: omc engine coupler

it shows 73-76 140 is 982511 for the coupler

Ayuh,....

That's Too Old,... The Outdrives were Totally Different back then....

 

[m2hunt]

Re: omc engine coupler

if i get 982511 couple will this still work even tho they are diff

 

[Bondo]

Re: omc engine coupler

if i get 982511 couple will this still work even tho they are diff

Ayuh,.....

Why would you want to buy the Wrong 1..??..??

You need a 983902 OMC coupler for your older engine. The newer engine with the one piece rear seal takes a 986917 coupler.

 

[m2hunt]

Re: omc engine coupler

i put the wrong number in. i dont like doing things twice i have been told that even if i find a coupler for the 2pc seal block that my outdrive wont work with it i dont know what to do i was told the 140 merc was the same as omc then i find out 86-93 block is what i should of been looking for i dont like spending money for no reason i just want to get this motor back in and working right if the number u gave me would work with the new stile outdrive thats fine i dont want to buy it and find out it wont work
my self i have been turning wrenchs for over 25yrs and the boats are diff very diff but thanks for all the help i have been getting here i am just stuck between a rock and a hard place

 

[Don S]

Re: omc engine coupler

i am just stuck between a rock and a hard place

You are creating the rock and the hard spot, there really isn't one. I've already done the research for you. As Bondo stated, the 70's models were for stringer drives, and completely different.

You need a 983902 OMC coupler for your older engine. The newer engine with the one piece rear seal takes a 986917 coupler.

So that leaves you with 2 choices. Either follow the above advise, or listen to your "i was told" source. It's up to you.

 

[m2hunt]

Re: omc engine coupler

but when i pull that part number up it shows 86-90 and those have the one pc seal the bolt patterns are diff older block has the bigger bolt pattern on the crank

 

[Bondo]

Re: omc engine coupler

Ayuh,....

While I don't Do OMCs,.....

I looked in the Serria catalog at the Merc listings,...
There are couplers listed for both crankshaft bolt patterns,....
18-2171 is the older bolt pattern of, I believe 3,1/4"...
18-2172 is the 3" pattern for the late model Chevy crankshaft pattern....

I guess the Question is,....
Are the OMC crankshaft mounted couplers the same Length as the Merc crankshaft mounted couplers,..??..??..??

Now,.... I've Seen 1 Once,.....
And,...
I know the bolt pattern is the Same,...
And,..
The Spline count,+ diameter are the Same,....
But,...
I never measured to see if the crankshaft to driveshaft lengths are the Same......

Did the little 3.0l go to the smaller bolt pattern at the same time as the V6s,+ V8s,..??

Where I've been looking, they go by serial #s,.. Not the Year....

 

[m2hunt]

Re: omc engine coupler

I konw what u mean on the OMC this is my first and last from what i found out it is a good thing it isnt the older omc i have always ran merc last couple of boats had 165hp and those were great motors and still are
but i am glad u see the problem i am having the coupler for the 1975 merc
the 18-2171 does have the 3 1/2 bolt pattern but isnt long enough and is used with the 2pc rear seal
and the 18-2172 is the converson from 3 1/2 to the new 3" bolt pattern but what i have seen so far is the length is the problem merc is 4 1/4 and my omc need to be 5 9/16 thats over a inch diff and i dont want to play with that
i have been looking at crowley marine in the parts they show a complete parts digram and for my 1990 it goes by model numbers witch mine is 302-bmrpws and it shows 3854032 and when i try to run that it comes up volvo
now when i run the 75 merc they go by ser. number for that year and that coupler is 76850a2 and is replaced 18-2171 ser. on it is 4481999
so what i am getting at is their is a converson from 3 1/2 to 3 but were is it at for 3" to 3 1/2 with the length i need and if i have a spacer made and use longer studs the coupler will bottom out
i know some one has had this problem befor just need to know how the solved it

 

[m2hunt]

Re: omc engine coupler

i found a man that crossed some numbers for me and it came up as a 18-21751 this one has the 3 1/2 bolt pattern and is 5 1/2 long i want to thank you guys for all the help
and note i will not buy or trade a nother omc from here on out its merc i have never had problems finding parts or working on them
thanks mark

 

[Bondo]

Re: omc engine coupler

have been looking at crowley marine in the parts they show a complete parts digram and for my 1990 it goes by model numbers witch mine is 302-bmrpws and it shows 3854032 and when i try to run that it comes up volvo

Ayuh,....

OMC,+ Volvo did a Joint venture, Just before OMC went under....

I gotta believe that Volvo # is the coupler you Need....