OMC 3.0 coupler question

[TwoBallScrewBall]

Hi, <br /><br />Well I got the flywheel I needed, now my problem is the coupler. I have an 1988 boat and outdrive that I'm putting a 2002 block into. It's a 3.0 OMC. I have a coupler with the correct bolt circle and splines, but I have a question. On the original engine, the crank had a hollow recession in it that a protrusion in the coupler sat in. The new coupler also has this protrusion, though smaller, but the crank ont he block I have does not have a recession to accept it. The crank is basically flat with the exception of about a 1/2" cone-shaped hole in the center. <br /><br />What coupler do I need?

 

[TwoBallScrewBall]

Re: OMC 3.0 coupler question

I measured and if this coupler did not have the protrusion and sat flat against the flywheel/crank, it would measure exactly the same distance from the back of the block to the end of the coupler as the original one does. Can I just have the protrusion machined off?

 

[TwoBallScrewBall]

Re: OMC 3.0 coupler question

bumpety bump.

 

[akriverrat]

Re: OMC 3.0 coupler question

is this protrusion about like the end of a manual transmission input shaft and whatever the bearing in the end of the crank is called? brain fart. 25 years since i played those games. pilot bearing!! if so, could the crank be drilled to accept this? since the coupler doesn't spin in that hole tolerances wouldn't be critical and hand drilling should be acceptable

 

[Bondo]

Re: OMC 3.0 coupler question

Hi Steve,<br />akriverrat brings up the Question, Why is there No Pocket for the Pilot Bearing ????? <br />Is there, by chance, a plug of some sort in the pocket of the crank ?????<br />If Not, I would rather Grind the protrusion to fit the Crank,<br />Instead of Drilling my Crankshaft.......<br /><br />Either Way,<br />I Can't see Any Real Issues.........

 

[TwoBallScrewBall]

Re: OMC 3.0 coupler question

To clarify, the coupler is aluminum, and on the side that faces the crankshaft there is a protrusion that normally sits in a hole in the crank. The crank on the 2002 3.0 I have is flat, no hole, so the coupler did not sit flush. The crank on the 1988 3.0 has the hole. <br /><br />Here is a picture of the coupler. You can see the protrusion that I'm speaking of. I already took the liberty of band-sawing the thing off and very carefully grinding it perfectly flat on a belt sander. Fits perfectly now and measures out exactly as the original did on the original block. I agree Bondo, I'd rather mess with the coupler than the crank.<br /><br />I just wanted to double check with you guys to see if there was any big reason for the protrusion/hole setup. As far as I can tell with the six crank studs it shoudl be adequately secured and centered. <br /><br />Anyone else please feel free to chime in with your thoughts!<br /><br />

 

[akriverrat]

Re: OMC 3.0 coupler question

mostly just threw that out because your 'bumps' did not seem to be attracting much attention. after seeing the picture i was way off base. looks like taking it off or new crank.

 

[Mark C.]

Re: OMC 3.0 coupler question

Hi Steve, The coupler in the picture looks alot<br />like one I had on an old mercruiser inline 6 cylinder. It was held by the studs only, it didn't have the extra pilot. You may want to talk to a omc dealer, they may have an updated coupler. <br />I changed from a 1988 3.0L to a 2002 3.0L mercruiser in my boat too. <br />I feel your pain. <br />Mark

 

[TwoBallScrewBall]

Re: OMC 3.0 coupler question

Hey Mark,<br /><br />Believe me I've worn out my phone, chopping the thing was the last resort. My Brithday is April 16 and I have given myself a goal of being out on the bay for it so I'm getting down to the wire here. This style coupler for OMC is not available anywhere without the bump on it for the crank hole. The only other option I was offered was to use a different style coupler that bolted to the flywheel instead of the crank, but then the bellhousing I have would not fit and nobody could find one that would. I think the modified coupler will work fine, but I should know for sure in a month or so! <br /><br />Riverkat, I appreciate the suggestion anyway! <br /><br />Thanks again everyone.

 

[TwoBallScrewBall]

Re: OMC 3.0 coupler question

Just an update, I've got about 20 hours on the engine and the modified coupler, and not a hint of trouble. No vibration. So far so good! I think the key was to make sure to not modify the actual mating surgace and to only remove the pilot bump and nothing else. <br /><br />Of course, now that I posted this..... <br /><br />Thanks again!<br /><br />PS - And yeah, I made my April 16th goal (made a trip or two to Boat/US that day, but I was in the water at 3:00pm), and it very well may have been my best birthday yet.

 

[Bondo]

Re: OMC 3.0 coupler question

Glad to Hear it went Well................<br /><br />You get a Gold Star......<br />And, <br />An A+ in "Creative Engineering" this semester..........