Newer Chevy 350 coupler for older OMC

[Carsto]

Hi guys, I have an 1985 Bayliner that had a blown 305 engine. I recently built a 350 engine that came out of a 1995 Chevy pickup. It is all ready for install but since the old engine has the 2 piece rear main seal and the new one has the 1 piece the coupler doesn't match up to the flywheel. Is there a new coupler for the newer engines?

 

[Bondo]

the coupler doesn't match up to the flywheel. Is there a new coupler for the newer engines?

Ayuh,..... Welcome Aboard,.... Which drive ya couplin' it up too,..??

Have ya got a new flywheel that fits the motor, of the same outer diameter of the ole flywheel,..??

If it's the little rubber donut coupler that goes onto studs on the crank shaft, Yes, Sierra has a retro-fit coupler, 'n iboats carries the Sierra line of parts,....
Click on the parts link at the top of the page,.....

 

[Carsto]

Thanks! I am attaching to a stringer outdrive. The current coupler is just a steel plate with splines. I have the flywheel that came with the new engine. It is larger in diameter but I have the correct starter for it as well.

 

[Bondo]

I have the flywheel that came with the new engine. It is larger in diameter but I have the correct starter for it as well.

Ayuh,.... Will the larger flywheel clear the flywheel cover for the drive,..?? The mid-section housing,..??

Is the motor's block drilled for the 12" flywheel starter mountin',..??

 

[Carsto]

The larger flywheel will not work I just checked! Also yes it is drilled for the other starter.

 

[Bondo]

Ayuh,.... So ya need the 12" flywheel, 'n starter,..... yer coupler should bolt right up to it,.....

 

[Scott Danforth]

Bondo, most of the OMC's used a button coupler that bolts using the flywheel mouting bolts. the problem with stringer drives, is a coupler doesnt exist for the 1-piece crank seal, except for one aftermarket company that used to spin them up on a lathe.

however you can get the ford coupler and adapt it
http://boating.forumsee.com/a/m/s/p12-56850-016554--one-piece-rear-main-chevy-800-stringer.html

 

[Carsto]

Thanks, if I adapt the ford coupler will I need the spacer for the bell housing as well? If I do doesn't that mean the front motor mounts will need moved?

 

[Bondo]

Bondo, most of the OMC's used a button coupler that bolts using the flywheel mouting bolts. the problem with stringer drives, is a coupler doesnt exist for the 1-piece crank seal, except for one aftermarket company that used to spin them up on a lathe.

however you can get the ford coupler and adapt it
http://boating.forumsee.com/a/m/s/p12-56850-016554--one-piece-rear-main-chevy-800-stringer.html

The current coupler is just a steel plate with splines.

Ayuh,.... That sounds like a flex-plate coupler that bolts to the flywheel, usin' the pressure plate bolt holes used in a truck,....

 

[Scott Danforth]

going to need a picture. most of the OMC couplers are a little plate about 5" round with the small bolt pattern for the crank and a little hub with splines. If it is a flex plate coupler, it will bolt to almost any GM flywheel.

 

[Carsto]

I tried uploading pic but it was too large. The plate is about 5" in diameter with 6 bolt holes and it is mounted to a flywheel not a flex plate.

 

[Carsto]

No Title

I found a picture of what my current coupler looks like. The ford coupler looks like it would work but not sure about using the 3/8 adaptor for the bell housing.. Does it need the adaptor for the bell housing?
Also could I just weld in the old holes of the old coupler and drill new ones? Just a thought.. I'm trying to finish this project as cheap as possible.. Thanks!

 

[Bondo]

Ayuh,.... That looks to mount to the crank shaft studs,....

Not the flex-plate coupler I've seen,.....

I'd probably go with the adapted Ford unit, as it's proven to work,....

Yer's is to big in diameter, 'n the wrong bolt pattern,.... 3, 1/4", vs: 3",....

How square are the splines in that old piece,..??

 

[Scott Danforth]

Could probably drill a new pattern between the existing holes

 

[Carsto]

I figured it out! I bought an adapter for my engine to install the older style 2- piece seal crankshaft. I had an old crankshaft laying around so I swapped it out and now the flywheel and adapter fit!

 

[Scott Danforth]

did you mike or plastic gage the bearings at a minimum?