engine coupler adapter from 81' 3.0 to 91' 3.0

[mattyrich]

Hello there. maybe someone has conquered this problem before.

trying to drop an older 1981 mercruiser 3.0 into a 1991 bayliner whick previously had a 1991 mercruiser 3.0. I am aware of all of the other compatability issues, but this is the last obstacle that im facing.

Both motors have a 12 3/4" flywheel. older motor has the coupler that bolts to studs on the crankshaft and in turn holds the flywheel on.

newer coupler that i need to get on there to match up with the alpha one yoke (drive shaft) bolts to the outer edge of the flywheel.

The only real problem that i have getting the new style coupler to fit is that the studs from the crankshaft, coming through the flywheel come out about 1/4" inch too far for the new coupler to fit flush on the flywheel like it needs to to have clearance from the flywheel housing...

I am wondering if i can make a spacer plate that looks like the base of the older style coupler to hold the flywheel on, then cut about a quarter inch off of the studs so that they will not interfere with the back of the newer triangle style coupler. That way I could use the newer style flywheel housing with the correct mounts to match up with my gimbal.

Ive seen a bunch of different styles of aftermarket couplers on line but im not sure if any of them will work. Anybody solved this problem in the past?

My under standing is that the older style coupler will stick out too far from the flywheel so that the drive shaft from the outdrive wont be able to go in far enough because the splines are not long enough. Could I replace the yolk? What do you guys think I should do??? Thanks, Matt

 

[fishrdan]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Remove the studs from the 81 crank and use the crank bolts from the 91.

 

[mattyrich]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Thanks for the tip, i was thinking that i may be able to do that but wasn't sure if i could get those studs out. Do you know how to do that or if it's possible for sure? i dont want to mess anything up. Have you done this before? any help would save me alot of hassle, money, stress, and this engine...

THANK YOU VERY MUCH,
Matt

 

[mkast]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

http://buy1.snapon.com/catalog/item...&group_ID=1247&store=snapon-store&dir=catalog
This is the expensive way.
The cheap way is to use a double nut arrangement.

 

[Bondo]

Re: mercruiser 3.0 crank shaft, changin studs?

Re: mercruiser 3.0 crank shaft, changin studs?

i would like to change them to bolts so that the newer style (post 1991) engine coupler will fit onto the flywheel.

Ayuh,... That coupler, I Believe, won't fit inside the flywheel cover on an 81 vintage drive/ motor combo...

I think iboats sells the Sierra conversion Coupler for what you're doin'...
It's the old style coupler for the new 3" crankshaft bolt pattern...

Btw,... Yes, the studs just screw into the crankshaft....Double nut 'em to get 'em out...

 

[Don S]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

I merged the two threads on the same subject together, and removed the duplicate info.
Please just post one time an a subject, even with different titles, it's still the same question.

 

[mattyrich]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Thanks Don, sorry about that mistake...

So... does anyone know how to find the sierra coupler conversion from early 3.0's to late style triangle coupling?

I think i know what was meant by the "double nut solution", but the studs from the crank will still be a bit too long, and therefore hold the triangle coupler off of the flywheel which inhibits it from spinning free from the flywheel cover. Should i just make a 5/16th's spacer with six holes drilled in it to hold the flywheel on to the crank and compensate for the non-threaded part of the studs (left from the removal of the old style coupler), and cut a bit off of the end of the studs so it doesn't hit the back of the triangle coupler that mounts flush to the flywheel? This would probably ruin the crank in terms of converting it back to the old style coupler, but I dont think i would ever need to do that. whats the best/cheapest solution here?

P.s. The LENGTH of the studs are the only thing holding the triangle style coupler from mounting flush to the flywheel. therefore, its slightly rubbing on the inside of the flywheel/motor mount cover?

Do the studs come out, and if so, How?
Thnks guys

 

[Bondo]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Thanks Don, sorry about that mistake...

So... does anyone know how to find the sierra coupler conversion from early 3.0's to late style triangle coupling?

I think i know what was meant by the "double nut solution", but the studs from the crank will still be a bit too long, and therefore hold the triangle coupler off of the flywheel which inhibits it from spinning free from the flywheel cover. Should i just make a 5/16th's spacer with six holes drilled in it to hold the flywheel on to the crank and compensate for the non-threaded part of the studs (left from the removal of the old style coupler), and cut a bit off of the end of the studs so it doesn't hit the back of the triangle coupler that mounts flush to the flywheel? This would probably ruin the crank in terms of converting it back to the old style coupler, but I dont think i would ever need to do that. whats the best/cheapest solution here?

P.s. The LENGTH of the studs are the only thing holding the triangle style coupler from mounting flush to the flywheel. therefore, its slightly rubbing on the inside of the flywheel/motor mount cover?

Do the studs come out, and if so, How?
Thnks guys

Btw,... Yes, the studs just screw into the crankshaft....Double nut 'em to get 'em out...

Ayuh,... Double Nut 'em, 'n Screw 'em Out...

Is this going into an 81 boat/ driveline, or a 91 boat/ driveline,..??

 

[mattyrich]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Thanks bondo,
this motor is 1981 merc 140 3.0 that is going to be dropped into a 1991 bayliner that had a 1991 mercruiser 140 3.0l and alpha one outdrive. That is why im trying to put the the new style coupler and flywheel cover on the old motor so that the mounts will line up and the drive shaft will slide in uninhibited just like before. So double nut the studs on the 1981 crank, and turn a breaker bar counter-clockwise and the studs will screw out of crank? I assuming, if that works, I can just use the same thread bolts from the 91 to hold on the flywheel so it wont hold off the triangle style coupler and inhibit the flywheel from spinning freely in the housing. Right? Please tell me this will work!!!!! Thanks a whole lot bud,
Matt

 

[fishrdan]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Remove the flywheel from the 91 and see if it fits on the 81, could be the same flywheel, maybe not. Once you get the flywheel off you'll be able to see if it's a 2 piece rear main seal or 1 piece rear main seal. Somewhere along the line, they changed to a 1 piece rear main seal on the 3.0's and the crank bolt pattern also changed at that time.

Heck, you could measure across the studs/bolts and see if they are the same pattern, center to center measurement across the bolts/studs.

If the flywheel fits, just use everything off your 91 engine: flywheel, bolts, coupler rear, engine mount.

 

[mattyrich]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Thanks to Fishrdan, bondo, Don, everybody else, and a little luck, I was able to conquer the issue of swapping the engine coupler and flywheel housing so that the 1981 merc 140 3.0 will mount into my 1991 bayliner with a 1991 mercruiser alpha one outdrive!!! Fishrdan, the flywheel's were both 12 3/4" flywheels, but the bolt pattern was different. 91' was 3", and the 81' has a 3.5" bolt pattern. luckily i had both! I was able to get the studs out of the crank with vice grips, no problem at all. I then used the bolts from the 91' to mount the 81' flywheel to the 81' crankshaft...

I proceeded to bolt on the triangle style coupler to the 1981 motor with no problem, and i installed the flywheel housing just to be sure that it would fit...

Wah lah' it fits now, and I cant see any reason that the motor shouldn't drop right into place of the one i took out. I am so relieved now, but I still have a couple issues to deal with...

For example, exhaust elbow is straight down on this motor and the transom is set up for a exhaust elbow with a 45 degree angle. I have a couple of them, but im not sure how good they are. do they need to be in great shape or what? can i just remove any flaky rust from the inside and use one of the ones that i have?

Also, I have to find a way to put a little extension arm on my Rochester carb to accept the existing throttle cable i have in the boat which was compatible with the 91' 3.0... Any ideas?

Other than that, I just gotta put some gast and water to this thing and hope it runs nice... I have perfect compression and spark, so I hope I dont run into any big problems. Any advice on these subjects would be graciously accepted.

I'll post pictures of the finished flywheel project tomorrow as its to dark now. THANKS TO EVERYONE AND TO IBOATS FORUMS... WOO HOO!

 

[EddiePetty]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

(Referring to Post #1, picture #1)

....check those Welsh plugs (aka freeze plugs, founders plugs, molding plugs) before you close the deal. They sure look ferrous from the pictures.

 

[mattyrich]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

Ok, what do you mean by check the freeze plugs? just make sure they are sealed up good and such.. I am going to take the flywheel off one more time and brush some naval jelly on the block to remove all of the surface rust. I'll rinse it with water and wait for it to dry and then add some good paint to hinder the reformation of rust. Any suggestions? Thanks for the advice, Matt

 

[EddiePetty]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

...assuming your engine is raw water cooled and has the potential of being run in salt water, ideally the 'freeze' plugs should be brass instead of steel.

 

[Eric 3.7LX Alpha 1]

Re: engine coupler adapter from 81' 3.0 to 91' 3.0

...assuming your engine is raw water cooled and has the potential of being run in salt water, ideally the 'freeze' plugs should be brass instead of steel.

Ohhh, that one at say 2 o'clock looks pretty rusty. Use something sharp and cut a scratch into it and see if it's yellow or silver.

Gonna be a lot of work to fix a leaker once she's back in bolted up.