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Just to set the stage, I KNOW NOTHING, basically.

I picked up an SST60 tunnel from Mercrazy last spring and have been running it with a 1991 Evinrude short 40 which is fun for figuring out how to drive it. For this year I have the parts to turn it into a ‘50’ (I hope) including a 50 intake, head, and a set of carbs off an ’81 Evinrude 75.

So, next on the list I have a couple of long shaft 3 cylinder motors, the 1981 Evinrude 75 and a 1986 Evinrude 70 that I hope to either cut down or modify to a short shaft.

Has anyone had any success using the stock long shaft clamp and trim on a short or cut down mid?

..and..

Has anyone had any success cutting and welding drive shafts?

All advice welcome…

Thanks!

The key part of your project and the most costly is finding a GOOD! nitro or SST60 lower unit.
You can find the correct mid and clamp brackets......Top Gun has 15 inch mids with 75 hp running powerheads on this site for $400.00 for example.
viewtopic.php?f=27&t=4102
For a well used lower unit you will pay over $700.00 Canadian.....to freshen it with new gears will cost you another $1000.00 Canadian,
A tired used nitro and a tunnel has a very short life......it has to be fresh!
You could run the large lower unit with the shortened drive shaft and shift rod and a 25 to 27 pitch prop. Less initial cost but the less resale value and poor performance compared to the nitro.
I suggest you start by getting the lower unit.
https://www.screamandfly.com/attachment ... 1401718728

I know that boat has always had OMC engines on it but VISA88 has sst90 Mercs for sale. The two stingers Top Gun had have sold.

Here is an example of a nitro for sale
https://www.ebay.ca/i/253905286789?_trk ... noapp=true

Guys,

Thanks so much for the awesome advice. I will keep my eye open for a nitro that doesn't break the bank. For now the large cases seem to be self-propagating in my shop, so I'll start with those and swap it out when a nitro comes up.

My son is a welder so I was hoping to trim the driveshaft back on the lathe and weld the splined section back on. I am a bit worried about balancing it

Looking at the 20" clamp and trim, it looks like with a bit of gentle surgery I could preserve most of the steering range.

Thanks!

Here is a post where the fellow shortened a 20 inch 70 hp mid section and used the clamp bracket.
http://www.boatracingfacts.com/forums/s ... lv-trailer

That's some serious surgery! I was hoping to trim the stock clamp just ahead of the trim mount and just relieve it enough to allow the lower engine mounts swivel without interfering with the side of the clamp.

That way I was hoping to keep the stock trim unit.