engine not spinning prop hub good coupler good

[thestigmach1]

I have a 1985 searay 19ft with 230 mercruiser. Replaced coupler and prop last year. While out yesterday cruising the engine suddenly went high in rpm and lost forward motion. No forward no reverse noticed at that point that the engine temp was a bit high. Got towed in messing with it on the trailer checking for bad hub or coupler. Had someone spin prop while in gear while I watched coupler and the shaft does not spin. Took prop off and marked it, put it back on and spun it. Marks did not move and output shaft spins fine. Prop is fairly easy to turn even though it's in gear. There is a rubber rubbing noise when spinning prop. What could be the problem?

 

[Bt Doctur]

either a broken lower driveshaft , or the upper unit ran very low on oil and melted the gears

 

[thestigmach1]

Upper unit has plenty of oil. I took the top cover off to see what it looked like in there and it came off explosively which I thought was weird. But it looked ok in there. What's the best way to verify? I didnt think a shaft would just break because it felt like it.

 

[Bt Doctur]

Yea, it would just break. drain the oil and shift into Fwd, drop the lower unit and I`m sure you`ll find the top splines sheared off

 

[thestigmach1]

Wonderful. Dont have time to mess with it today. I'll post back with what I find later in the week.

 

[thestigmach1]

Is it normal for the top cover to come off with such force that it flew up, smacked the swim deck, and ricocheted to land 4ft away? I've never taken the top cover off one

 

[thumpar]

The rubber you heard was probably the impeller. If he upper gears look good then the shaft probably broke.

 

[Grub54891]

Is it normal for the top cover to come off with such force that it flew up, smacked the swim deck, and ricocheted to land 4ft away? I've never taken the top cover off one

Never had that happen. Was it just after running it on a hose?

 

[nola mike]

Usually it takes a bit of prying to remove the cover

 

[thestigmach1]

Never had that happen. Was it just after running it on a hose?

No this was the next day after it broke. Scared me half to death. I figured it would pop off but not explosively. I found a prealpha drive off a 4cyl cheap. I know the lowers bolt together and the whole thing will bolt up to my alpha 1 gimbal. I remember years ago when I swapped a 6cyl out for a v8 and I put the 1.5 ratio drive on the shafts were different lengths though. Would this 4cyl drive be the same length as my alpha 1? Or is one longer than the other?

 

[nola mike]

Uppers on the mc-1s have the shorter input shaft.

 

[thestigmach1]

Uppers on the mc-1s have the shorter input shaft.

So I wont be able to do my original plan of swap the whole thing?

 

[nola mike]

I think it will work, you just need to change out the yoke. Someone will correct me if I'm wrong

 

[thestigmach1]

I think it will work, you just need to change out the yoke. Someone will correct me if I'm wrong

The yoke part is what I coupdnt remeber if it was different. Does anyone have a 1.5 ratio alpha one laying around to measure the shaft? Before I go and yank this one off the boat.

 

[nola mike]

The yoke is different on the mc1. It isn't dependent on the drive ratio

 

[thestigmach1]

The yoke is different on the mc1. It isn't dependent on the drive ratio

The reason why I say that is when I went from the 1.92 ratio to the 1.5 ratio with an mc1 the yokes were different length and i had to swap them out. Seems like the 1.92 ratio was longer but have them reversed. But one was a lot longer than the other.

 

[nola mike]

Then I guess I'm not sure. Mid 70s I think some things changed on the mc1 with the trim sensor location, but idk if that affected the outdrive or just the bell and/or gimbal housing. Either way, a later mc1 will bolt up. If you need to swap the yoke it's NBD. Not sure how you went from a 1.92 gear ratio to a 1.5 though...

 

[nola mike]

Just rereading your post--did you plan on replacing your alpha 1 1.5 ratio drive with a 1.94 or similar mc1? You probably wouldn't be able to prop around that.

 

[thestigmach1]

Just rereading your post--did you plan on replacing your alpha 1 1.5 ratio drive with a 1.94 or similar mc1? You probably wouldn't be able to prop around that.

Yes my plan was to just swap out the entire alpha one for the mc1. I know it's not right ratio but I'm over propped, wot is 3500, so figured that would get it up right and it all work. The reason I'm wanting to do the whole thing is I'm afraid to get the lower apart and find that it destroyed the teeth in the upper where the lower slides into. Is it common for it to destroy the teeth in the upper? I also dont want to pull the whole thing off to find that the yokes are different. Someone wants to trade a bigger boat for this boat so time is short on getting it back together to just order new ujoints to swap out the yokes. I dont want to do it so that I'm screwing the other guy, that's not my thing it all comes around in the end. but I also want to do it with the least amount of work as possible. To get it running for the trade on hopefully sunday.

 

[thestigmach1]

So as you guys said the yoke is shorter by roughly two inches on the mc1. My understanding was that the mc1 lowers will go in the alpha 1 uppers. However this on will not. Much less splines than on the alpha 1. Also found that the shifter shoe turns the wrong direction on the mc1 to just swap out the yokes and be done. Did I misunderstand that all of these things are supposed to work?