Gear housing assembly interchangability?

[ttownthomas]

I'm mid restoration on a 1972 Bertram 25 with twin Mercruiser 165's. One gear housing assembly has a broken skeg and cavitation plate and now that I have striped the paint off I have found a hairline crack about 5 inches long in the housing. How interchangeable are the housings? The one that came off the boat (and it dosen't match the other drive btw) is part number 1623-8950. I found a NOS housing online but it is part number 1623-2406. Will my innards swap into this new case? And how hard is that swap?

 

[Bt Doctur]

Forget the restoration and bolt on Alpha`s There is a old 8 spline and the newer 12-13 spline not interchanable

 

[ttownthomas]

Forget the restoration and bolt on Alpha`s There is a old 8 spline and the newer 12-13 spline not interchanable

Can you please elaborate on this statement? I assume you mean throw out the drives and buy 2 new alpha drives instead? And bolt them up to my gimbal bell housing. Do you mean SEI or actual mercruiser?

Where do you count the splines to see if it is 8 or 12-13

 

[kenny nunez]

Listen to the doctor. While it is possible to swap the internal parts it takes some special shimming tools to get the back lash and pinion height set to specs.
Of course genuine Mercruiser drives are the best but there are a lot of the SEIs that have been sold and appear to hold up.

 

[Bt Doctur]

Count the splines on the lower driveshaft, they match the gears in the upper

 

[ttownthomas]

Count the splines on the lower driveshaft, they match the gears in the upper

13 splines on the top of the drive shaft assembly. Not that it matters I think. I'm Fully leaning towards replacing the drives with alphas. Just watched an 8 part video about dissembling the lower unit. There it a-lot to it. By the time I buy the tools and the case I'm almost at the cost of a replacement. Thanks for the advice.

I think I need a short yoke with 1.62 gears....Can anyone confirm this? What does the 1.62 mean? Is it that the propeller turns 1.62 times for every engine rotation or that the engine rotates 1.62 times for every turn of the prop?

 

[ttownthomas]

I think I need a short yoke with 1.62 gears....Can anyone confirm this? What does the 1.62 mean? Is it that the propeller turns 1.62 times for every engine rotation or that the engine rotates 1.62 times for every turn of the prop?

Found this answer

 

[ttownthomas]

If both my upper units are in decent shape is there any reason to not just replace the lower units instead of the entire drive(s)? Is there a test that can be done or an inspection process to determine the condition of the uppers?

 

[Bt Doctur]

If both lowers are 13 spine, then just the lower need replacement 13 spline are the later MC1`s abd Alphas

 

[ttownthomas]

If both lowers are 13 spine, then just the lower need replacement 13 spline are the later MC1`s abd Alphas

Very good. Thank you