hagstal

Hello,

I'm almost done with a transom repair/replacement on a 1979 Formula 233. The transom has an 11 degree angle so mercruiser recommends an x dimension of 14", that would put the output shaft centerline at 8.25" below the keel. I will be replacing the engine stringers/mounts too so raising the engine shouldn't be a big deal (unless the engine cover becomes a problem). Someone had replaced the original OMC with a 7.4 bravo 1. They had set the x dimension at 14.25.

This has been an ongoing project for quite a few years. I've never had it in the water. I've rebuilt/modified the carbureted 454. Forged crank, 420 pistons and connecting rods, voodoo cam, dart heads (310 runners), performer plus intake, edelbrock 750 carb. I'm hoping for over 400 hp. I'm sure the dart heads are very overkill and will affect my perfomance but I got a good deal on them.

I've read through a lot of x dimension threads but didn't see anyone that raised one on an old formula 233. I'm thinking 2" ought to be conservative enough but what do I know. Looking for opinions....

boatnuts

Unless you just want to go fast, I would go with X plus 1". That hull if I remeber correctly has a rounded over keel. If it is V'd to the heel go plus 1-1/2 to 1-5/8". That get the cavitation plate completely clear of the bottom on the outside corners.

hagstal

Thanks baotnuts,

X + 1 sound reasonable to me. I will be cutting the hole soon, hopefully within a couple of weeks. The keel is pretty rounded. Fast is good but, its main purpose will be fishing. Just want to have fun gettin to the fishing grounds quickly.

Here are a couple of pics of the project, as you can see the keel is pretty rounded:

Itsallgood995

I baught some parts from a guy here on oso a couple years ago who also had an old Formula. His transon looked different than yours but he raised his 4" & was impressed with the results. I'll PM his email if you want to follow up with him.

hagstal

Does anyone have a transom cutout jig I could borrow? If not I'll be cutting the hole using the paper template and a drill jig.

I still haven't decided on the x dimension yet.

Raising the x up 4" makes me a little nervous. I worry about cavitation when starting out with heavy loads (overloaded). I'm sure once on a plane it would be fine but don't want to fight it to get it there. When I go on fishing trips to various cabins the boats are overloaded with people, coolers full of ice, all the gear, full tank of fuel, food, cookware, camping stuff etc.

Still looking for input, seems like someone would have messed with x dimension or keel to prop depth on a 233...

dereknkathy

judging by what you plan on doing with the boat, i would put drive back where it was designed to go. this sounds like a 35 mph boat over 90% of the time.

hagstal

Part of the problem is I don't know what the factory x dimension was. Most likely it the mercruiser recommended 14". Before I ripped things apart it was at 14 1/4" (after someone replaced the old omc with the 7.4 bravo in 1989). I'll be cutting this weekend, still not sure what to go with. After people recommendations probably somewhere between 14" and 15".

stillcrazy26

Use the paper template. Make sure that you layout the centerline verticle and centered.Take your time. Get directions if you do not know how to do this. Use a pilot drill to mark the holes. When I first started installing drives, I had a jobbers length pilot drill and used to have a small piece of 2" aluminum angle that I would put against the transom. I would check it in two directions to confirm I was drilling straight. After that follow up with the hole saws and larger drills, they will follow the pilot. Next step is sawing out the opening. Watch so blade cuts straight. It can be done with a jig saw with a 8T blade. I did a few hundred of them. Seal the cut out.

mcollinstn

The factory X dim was from the era of aluminum 3 blade props. Regardless of which engine option you chose in that hull, the X was the same.

With 4 blade props being the norm these days, I would say you can safely raise the X and not suffer any drawbacks.