What all did I just break???

[justthisguyyaknow]

73 Starcraft with a 120hp 4cyl, and a pre-alpha sterndrive. I was in the water ready to ski, and my daughter had trouble starting it. I said give it a little gas when you start it.

Well, she proceeded to start it and immediately PUT IT INTO GEAR while it was still at a rather high rpm.

Surprisingly, the boat pulled me up on skis. Unsurprisingly, it stopped after about 2-3 seconds.

I got towed back in (I owe someone a case of beer), and back at the house have found:

1. While the engine runs, the impeller apparently isn't turning (no water is being pumped)

I then removed the outdrive and found:

2. Metal shavings in the grease around the engine coupler.
3. Moderate spline damage on the input shaft (not sure what it's called, but the driveshaft going from the engine coupler to the top half of the outdrive).
4. I found that turning the prop does turn the input shaft, and that forward/neutral/reverse does work.
5. Turning the input shaft, even in neutral, results in a horrendous noise from the lower section of the outdrive.

Now, in my mind this points to two independent problems, both damage to the lower half (the noise I'm hearing), and also damage at the engine coupler.

I'm beginning to question whether the boat is worth it if I have to pull the engine (which is tedious), replace the coupler, and rebuild the outdrive. Not to mention a bellows job and new shift cable which I'm at it.

I'm open to any opinions as to the best course of action at this point.

 

[jimmbo]

It is your boat, and your money, but unless the boat is immaculate, and has major Sentimental value, I wouldn't be willing to spend much money to fix a 46 yr old unit.
The impeller is located in the outdrive, so if the input shaft is turning and the upper gears are intact along with the vertical drive shaft, the impeller should turn.

 

[justthisguyyaknow]

Agreed on the impeller. I've inspected the coupler on the back of the engine as best as I can without pulling the engine (which is tedious), and it appears to have lost its splines. That would explain the no water pump.

As I mentioned, the outdrive does transfer the power as it should if turned by hand, but with great resistance and noise.

It's probably not worth pulling the engine, replacing the coupler, having the outdrive rebuilt, etc., to be honest. Thank you for the input.

 

[Rick Stephens]

Pop the top cap off the drive and look at the upper case gears.

Yeah, a stripped coupler means a pulled engine. That is just your (tedious) labor and the cost of a coupler. At least it doesn't have to come all the way out, just far enough to spin it and pull the flywheel cover.

 

[justthisguyyaknow]

I've found a complete 120/140 outdrive, which the seller says is in good condition, and should be pre-alpha for under $100 (and a 3 hour drive), so I will definitely pull the engine, replace the coupler, and bolt up the replacement outdrive. Will post back my luck.

 

[tank1949]

I've found a complete 120/140 outdrive, which the seller says is in good condition, and should be pre-alpha for under $100 (and a 3 hour drive), so I will definitely pull the engine, replace the coupler, and bolt up the replacement outdrive. Will post back my luck.

That's one good thing about MCs. They been around for a long time and plenty of used parts can be found.

 

[achris]

Any drive up to 1990 will bolt up. That includes MC1 (what you're calling pre-Alpha ), R, MR and Alpha One.... Just make sure you get 1.98:1 drive ratio. And make sure you have the short yoke (shaft that comes out of the front of the drive)...

Chris....

 

[thumpar]

If you can do the work I would fix it. Those 120's are good engines and super easy to work on. It sounds like you are on the right track for what needs fixed.

 

[stonyloam]

One thing to consider, you probably don’t need to pull the motor OUT of the boat, just lift it a bit and move it forward enough to be able to get on the coupler bolts, so it might not be all that bad.

 

[justthisguyyaknow]

Well yeah, there's a problem...

 

[tank1949]

Well yeah, there's a problem...

Ouch!

 

[justthisguyyaknow]

As a followup, I finally found the time (and a large Catalpa tree) to pull the engine and install the new coupler. I used the proper hardware for the rear mount (old style with the double-wound lockwasher and fiber washer).

Now trying to align it, I need to lower the front of the engine more than the front mount hardware allows. As I lower it, the alignment bar is clearly starting to engage into the back of the coupler, but then gets hung up. The lower I drop the front (ie- raise the coupler, since it's behind the rear mounting bolts), the closer the alignment bar is to being able to fully enter the coupler.

I feel like the gimble bearing is positioned properly, and the alignment bar is not getting hung up there.

Since I know not to mess with the rear mounting and to leave it as Mercruiser designed it, I'm stuck with only the front adjustment.

See picture: Is it permissible to remove the bits of hardware above the adjustment nut and replace with a single washer in order to get the front slightly lower to achieve alignment?

 

[justthisguyyaknow]

I hate to followup to my own post, but I'm looking at "12-892619A01 Rear Engine Shim Mount Kit for Mercruiser Engines", which appears to simply allow the rear of the engine to sit higher, and is a genuine Mercruiser/Quicksilver part. It comes with small stainless steel washers, which I guess are meant to sit below the double-wound lockwashers(?)