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Swapping two Merc outdrives

D

DWester

Regular Contributor
We have a 1974 Cobalt ski boat with a 6 cylinder Chevy/160 merc, and the outdrive is not well. We also has a boat from the early 70's (a bigger boat) that has the Ford 302/888 merc setup and the outdrive is working. Are those outdrives interchangeable or is there a spline difference at the crank or any other differences that would toss that easy fix?

The serial numbers are 3851871 and 3784669. Are the gear ratios different in the upper, lower or both for these two. I should be able to swap the input shaft shouldn't I?

Money's short and I'd like to get one out of two here if possible.

Thanks for your help!!!​
 
Ayuh,... The gear ratios are different, 'n the input shaft is an inch shorter on the I-6 drive...

The ratio is changed in the uppers,...
The lowers may, or may not interchange, due to spline count changes along 'bout that time....
 
bondo said:
Ayuh,... The gear ratios are different, 'n the input shaft is an inch shorter on the I-6 drive...

The ratio is changed in the uppers,...
The lowers may, or may not interchange, due to spline count changes along 'bout that time....
Click to expand...

If I was to change the input shaft to fit the I-6 and bolt it up, what would be the result. Could I change the prop pitch as mentioned above and maybe get by with that, or will it be to much of a difference in gear ratio for the I-6 to run?
 
Ayuh,.... The I-6 should be 1.84:1,... possibly 1.65:1, but probably not...

If the I-6 is Now runnin' a 17" prop, ya can't buy a small enough prop to get the 1.5:1 down to a 1.84:1...
 
I agree with Bill.
There is no substitute for the correct over-all ratio, and with very few exceptions, the engine always determines the final ratio.
You may be able to swap the shafts, but you'll still have an incorrect ratio.


Changes in prop pitch or diameter to accommodate for an incorrect ratio, never quite work.
It's simply the characteristics of hydro propulsion.
 
Well, you can't blame a guy for trying. Guess we'll have to bite the bullet and find the correct one.

Thanks a bunch for your help guys. Always appreciated.
 
The Merc 165 was very popular, and actually lived a rather long life span within the Merc power trains.
You can no doubt find a good used 165 drive.

In fact, you may be able to e-Bay the 888 drive and come out ahead.
Worth a shot.

Or.... what about over-hauling the Ford 5.0L and using the entire V-8 package?
No one ever complains about having too much power!

.
 
RicardoMarine said:
The Merc 165 was very popular, and actually lived a rather long life span within the Merc power trains.
You can no doubt find a good used 165 drive.

In fact, you may be able to e-Bay the 888 drive and come out ahead.
Worth a shot.

Or.... what about over-hauling the Ford 5.0L and using the entire V-8 package?
No one ever complains about having too much power!

.
Click to expand...

That's good to know there's plenty of them (165's) out there. As far as the Ford, he's wanting to get that one going after we get the ski boat up and running.....hopefully.:) You know how that goes. So many boats, so little time. The Chevy/165 only has 225 hours on it. Not bad for a 74. The motor looks like new. Outta be a good runner when we get it back together.

Thanks Rick.
 
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