Outdrive failure?

[candiaoh]

I have a 1989 4Winns with a Alpha One, Gen One outdrive. Bought it the summer before last. Took it our for a spin this past weekend and after about 20-30 minutes of operation (mostly at WOT) I made the turn to begin heading back to the marina and I got a big bang, engine revs and loss of propulsion. I immediately shut it down. I did a restart, slipped in into forward and the engine died. Same with reverse. If I was a little more aggressive with slipping it in gear, the engine reved. Once towed back to the marina and on the trailer, when the boat was placed in the forward position, the prop clicked when turned CW, and would not turn CCW. I did not do a reverse test. One other note. When we were idling out of the marina in the no wake zone I swear I felt more vibration than usual...but I have not had this one out much this summer and it wasn't enough (I thought anyway) to cause alarm, even attributing it to a rough idle since the engine was not to temp yet and had not been run much this season.

I did not run the engine much after the incident, so I cannot tell if the water pump was running. I did note at the time it was at normal operating temp.

 

[racerone]

Prop clicking one way in forward is normal.----They all do that.-----Check gears in upper part of the drive.

 

[Scott06]

Agree pull the top cap on the drive. On the gen ones with out the lube bottle if the input shaft seal leaks into bellow the upper drive gears run low on oil with predictable results.

As outlined above the gear test you did is normal. Likely pull the top cap look for metal in the lube if those are ok pull the drive and check coupler u joints and gimbal bearing

 

[candiaoh]

If the input shaft seal fails does that mean the entire outdrive is ruined or just the upper unit?

 

[Scott06]

If the input shaft seal fails does that mean the entire outdrive is ruined or just the upper unit?

Usually when you grenade the upper or lower the other unit is ok, but... metal pieces will get in the other half of the unit as they are connected from a lube stand point.

So while the bearings gears etc in the lower may be ok it will need to be disassembled and cleaned. Of course there are specialized tools (mercruiser Alpha drive specific not higher end mechanics tools) required... as well as a lot of experience doing this type of work.

you still have some diagnosis to do but in the event it is the drive not the coupler, generally the most cost effective way to get back on the water is a used good condition drive or a SEI aftermarket drive. With basic mechanical skill and tools you can bolt on a new to your drive and get back on the water

 

[candiaoh]

Thank you for the responses. Let's say it's the coupler, which I understand is an engineered failure point. A failed coupler would indicate another issue, such as engine alignment, gimble bearing, or an issue in the outdrive, correct?

 

[Scott06]

Thank you for the responses. Let's say it's the coupler, which I understand is an engineered failure point. A failed coupler would indicate another issue, such as engine alignment, gimble bearing, or an issue in the outdrive, correct?

most likely. they tend to last the lifetime if alignment is ok. Alignment can be off from sagging engine mounts , gimbal, bearing going bad or rotten stringers and transom.

Would think the bang would be more indicative of drive exploding but could be splines on coupler too. Take a look and see what is going on

 

[candiaoh]

Drive was pulled. It appears prop seal failed. Both upper and lower units were destroyed. Good news is coupler, gimble and bellows are in good condition. My plan at this point is a used outdrive. I know I need to get a drive with the appropriate gear ratio and with the V8 it appears that is a 1.5 to 1.47. I understand that can be verified by counting the teeth in the upper drive? Beyond that, any buying advice on a used outdrive?

 

[Scott06]

Drive was pulled. It appears prop seal failed. Both upper and lower units were destroyed. Good news is coupler, gimble and bellows are in good condition. My plan at this point is a used outdrive. I know I need to get a drive with the appropriate gear ratio and with the V8 it appears that is a 1.5 to 1.47. I understand that can be verified by counting the teeth in the upper drive? Beyond that, any buying advice on a used outdrive?

Buying used would be nice to see what comes out with the gear lube- water / metal pieces vs clean gear lube. Would pop the top cap see what it looks like, and should pass a pressure test.

Look on the side of your current drive ratio should be stamped in it if not legible yes count teeth in upper. Gear charts can be googled...

Some of the larger V8s (5.7) used 1.47/1.50 ratio, while in my boat the 5.0 came from factory with a 1.62 drive. If you match what was there you you will have the same performance.

 

[kenny nunez]

I Have rebuilt many mercruiser drives that burned up the upper gear set. I just pulled the rear bearing carrier and flushed out the housing. New seals and upper gears, good as new.
What ever you do be sure that the drive can hold 10-15 psi. If the seller cannot show that keep looking.