Hot Boat

I have a 28' Scarab Excel that I am repowering. I am waiting for the motor to get finished but we are looking to see 575 - 600Hp. The problem is that I have a 1988 bravo 1 that had a leak in it a few years back. It still runs fine but I am worried about it with the new upgrade in power. I talked to a few places and they said I was better off looking to get a newer unit to rebuild than that one because of some internal upgrades over the years.

If I am going to get a newer drive should I look to get one with a shorter lower unit??? Would this give me any kind of benefit??? And if I decided to install a drive box extension in the future what would I want then, a standard drive or a shorter drive??? Am I going to see any real big increase on this hull with all this or should I just stick with the factory setup?????

With my luck I know I am going to blow the drive mo matter how careful I am. I'm just looking to plan ahead before she blows up on me.

Paul

Scarab28

Paul - I'm pretty sure my '89 excel has the same drive parts yours does. It made it through the first season (knock on wood) with the blower on it. Just take it easy out of the hole

Hot Boat

Scarab 28 What Hp are you running. would you have any idea what size prop and speeds I will see when this prodject is finnished????

cobra marty

Hot Boat, What are you running now. Tell me your boats weight, hp, wot mph and rpm, prop and pitch and I will figure your new speed and prop.

Hot Boat

Unfortunately I never got a true speed reading. but I think it was around 68 - 70 , The boat weighs 4600lb, That's the factory weight and I presume that is dry with out any equipment and fuel. It had 400 hp and was spinning a 15.25 x 22 p 4 blade @ 5000 rpm , It had a 23p mirage on it in the past and that spun @ 5300-5400rpm. I hope this info will help. Thanks Marty. This will be a great help.

Paul

B.R.S.

Hot Boat I'm running 547 horse through my original 1988 bravo's and so far no problems. Take it easy out of the hole and work the throttles when air borne. I use synthetic oil and change it often. 27 props at 5400 rpm and 81 mph but I do have to keep my fingers crossed.

Mr Gadgets

Hotboat,
I know of a friend that is running over 700hp thru one of the 88 drives. You would be better off to run a three blade prop rather than a four. A mirage will allow a bit of slip on acceleration and be easier on the drive. The four blade will give you too much bite and could cause problems. There are a lot of older drives holding up. Seems the newer ones fail if you sneeze at them..
Good luck... and enjoy it till is does let go.
As far as the shorter drive or stand off box, you need to look at your drive height,, too high (shorter lower) you will have trouble getting on plane or cavitation in cornering. A standoff box usually needs a four blade prop to help with hook up when coming on plane. Then you are back to more load on the drive. If you want to go to a stand off box, external steering is required. The newer "X" drives will handle your power level and four blade prop, then you could consider the standoff box. Will you go faster with the box, depends if you have trouble drying out the bottom. The box will give you more leverage to hold the bow up, allow you to run a bit higher drive height and keep the drive trimmed in some to get more forward thrust. If that is what your hull needs then you will see some increase in speed. If it works great without the extra leverage, well then a bunch of money is spent, but it will look cool with all the new hardware..LOL!!

Dick

cobra marty

HotBoat, Predicting the future is allways difficult but in your case You could probably see 78mph at 5450rpm with a 3blade Mirage prop and 77mph at 4950-5000rpm with a 4blade bravo prop. Good luck.