ToMorrow44

Wow 2" below the bottom, thats pretty high! But your boat runs well so I guess it likes it. Is the SC lower a shorty? I have a -2 Shorty and its still 4"+ below the bottom. From what I understand, for fast v-bottoms you can bring the drive height up until it won't get on plane anymore, so as long as it gets on plane without blowing out, it should be fine. I'd be interested to see how yours runs with the box as compared to before.
-Tom

lavey jr

Quent,

as far as I know there aren't any 2750's with a "full" box. There are quite a few out there with a Merc ITS which has about 9" of set back (not exactly sure)... All the 2750's with the ITS run and handle great, Uncle Dave's boat being one of them.

With your set up, 1.75" bellow should be just right. A 5 blade will be your best bet, which if memory is correct you already use one.
I know it's a different style boat but the 28 evo in it's original setup when it ran 105mph the prop shaft was right at the keel, maybe .5" above. We then lowered it 2" and it only lost a couple mph and it handles great!

Hope this helps.

-Jr.

Quent

Here are the dyno sheets from the pull on my 555 by Eric Betty at EB Marine. I was off a little on my numbers in the previous posts. These sheets don't show that the pull went all the was to the rev limiter, 6200, and that is where the engine made 1078 HP at 7 1/2 lbs of boost. Eric programed it fat so a small pulley can help if I ever needed it

Its worth noting that from 3000 to 5500 rpm that the torque was about 950 ish or better. That is a flat torque curve. Additionally, the engine kept making power all the way to 6200. I will prop the boat for 5800 to 5900.

Lavey Jr., thanks for the info on the outdrive. I am with you in that I think we are real close right where we are.

Quent

I picked my boat up Friday after Eric and I rode around and he fine tuned the motor. It is still fascinating to watch this whole process with Eric sitting on the floor of the boat dialing in the engine with a lap top. I suppose I'll have to finally say goodby to my timing light, dwell meter and box of Holly jets and power valves.

The bottom line is that I don't have a prop yet. I am borrowing Eric's 6 blade 32P 15 1/2" diameter Herring. At 5800 we ran 100 mph. The box feels like I have more bow lift and for sure the boat will stay on plane at a much slower speed. We stayed with a 1:5 gear and will prop to that.

Brett at BBlades is sending me a 34 stock Maximus and we can go from there. He feels that the 15 5/8" diameter will work well and he can pitch it up to 35 and deal with cutting the hub and potentially chopping off some diameter after some run time.

The Gibson mufflers are great. We can almost talk in the boat now. All in all, this is a good setup. The engine is by far the best piece that I've owned. I hope to see 105 consistently in hot weather. Time will tell.

Uncle Dave

Sounds like an absolute blast to drive.

Those are some mighty tall wheels you are turning there chief.

Lets see some picts!

Uncle Dave

Quent

So now after getting the box off and going back with the drive on the transom, Eric found that one of the brand new (12 Hours) Morel lifters broke a tie bar and snapped the roller off ruining the cam. At this point Eric doesn't know if there is additional damage.

Eric has done everything above and beyond pulling the motor to get the box off, reinstalling the motor just to find that the lifter was broken. He has the motor back out taking off the pan, removing the top end to put in a new set of lifters and cam. He has done all this in 3 or 4 days. I can't say enough good things about him.

Ain't high performance boating fun? Quent

Uncle Dave

Thats "high performance" for you. Hang in there brother......

UD