prop shaft height on 38 TG IV SSM rerig
 

Boats a '92 TG flat bottom notched transom and getting rigged with IV SSM's on boxes 1.5 ratio. Locally, I have a friend rebuilding everything and getting some info on shaft height. He's thinking at least 1-1.5" above the planing surface but thats an educated guess as of now. So I guess what I'm looking for is a second opinion so when we get together I already have an idea of were i should be. Also if anyone has experience with this set up, what a good starting point for props would be. I'm only running 500's but down the road will be blown (750-800hp range) so a used set of four blades will have to suffice til then. Thanks

ask Biggus.... He will know, he always knows!

That's a heavy boat, mild thunder will chime in I'm sure, he runs his 4's on a 38 fountain 1.5" below. I'd say with the boxes about even with the running surface. I have a jig for drilling and cutting the transom for Ssm's if you want to rent/ borrow it.

That would be great. Thanks!

I have a 38 topgun with #5 drives the gimbles are 6" from the notch

Send me an email we'll figure something out
[email protected]

Will do when i get a little closer. Thanks again

Boxes or not?

not i have #5 with 950hp with plug in trans

I think it will be difficult to get on plane with 4 blade props. My brother did a flat deck (no notch) with 4s and boxes and put the drive shaft about a 1/2 inch above the bottom. The boat does a big burnout with 5 blade, 17.5 diameter props. For an all around boat I would go around 1.5 below the bottom. At the speeds your going to see with 800s I don't think it will hurt you any.

But you can always space down, going up is tough.

Valid point!

First, think of the notch as an 8" box. Now your adding another box to that which is not a bad thing, but remember the farther back you go without going up is putting the prop in cleaner water but in affect(deeper).

Mercury boxes typically have 3 sets of holes. Neutral 1" up and 1" down. Your "U"joints in the half shaft can take that movement. I would set it at 1" above in neutral position. That way you can go up or down an inch without spacers. 2" above is as high as you'll ever go. And as Kvogt said down is alittle easier.

You will probably end up at least 1 inch below the hull.....especially with the lower HP. Two inches below may even work better with #4's. This will help with leverage to carry the bow. In my experience with #6 drives on a Kevlar Gun, 1" below the hull offered the best all around performance....even with 900 HP. Level with the hull worked better when running over 85 mph. The straight bottom Cigs always seem to like more prop depth.

The next problem will be getting on plane with #4's, since they don't trim in (tuck) nearly as much as a #6. That 1" below the hull will probably turn out to be very aggressive when trying to get out the hole.

Lots of great advice. Thanks everyone

Any guesses on a place to start with props. Definitely new to cleavers

Cool, the 2" spacers I`m getting should work out well then.
Any opinions on spinning the props in instead of out? I plan on trying the spacers first if that gets me on plane better I`m good with that.

Can you enlighten me on how you're set up now? Just out of curiousity?

icdedppl bought the boat from kvogt's brother.

icdedppl food for thought on your boat getting on plane... i rigged a fountian this year that has a notched transom. speedmaster #4s. previously the props ran about 1/4 above bottom of boat without boxes. was horrible to get on plane. took about a week lol. i put boxes on the boat and we set the prop about 1 inch below. boat handled like a ferrari and by 3k rpm the boat walks right on plane. scrubbed 1-2 mph off the top end but the stability on the top end and ease of getting on plane was worth the loss on the top end all day long

^^^^ Thats great news, yes it takes a week to get on plane as is :lolhit:

I think the spacers should make a nice improvement,
thank you.

Sounds like the common consensus is around 1" below hull maybe in bottom setting, can go up with more power, down if i have too with spacers.

Yessir!

Sounds about right. Mine has 6's not 4's, but is right around even with the bottom. It's perfect at speeds above 65 mph, but it requires me to drive it and constantly phuck with it below those speeds unless I want to keep the drives all of the way down. Getting on plane is not an issue for me, but Steve (CignificantOther) already explained that.....

On my boat with the Arneson drives, I tried both ways. My boat handled better with the drives turning out.

Dan's boat has big shaft IVs on 10 inch boxes. The prop shaft centerline is a little over a 1/2 inch above the bottom of the no-notch transom. This is a very aggressive set-up for the boat; the thinking was we would try big diameter 5 or 6 blade props or space down.