raising your lower unit for more performance?

[YOUNG]

I am pretty new to the whole boating thing. I have been very serious into the off road with rockcrawling and have never owned a boat until this year. I have been reading in several magazines and seen in catalogs where you can buy spacers to raise or lower your lower unit for more performance. My boat is a 99 Baja Boss Hammer with a MPI 7.4 and a Bravo one lower unit. Any answers or suggestions on this would be a big help. I have been wanting to squeeze as much oerformance out of my boat that I can with out really doing anything to the motor(cast pistons) and this is one of the things that I was wondering about. What actual part of the lower unit does this raise or lower? Are there for sure MPH gains or acceleration gains? Thanks Bryan

[Havasu Hangin']

I think you are talking about IMCO lower units?
For top end speed, the higher you can run the propshaft (relative to the bottom of the boat, or "X" dimension), the less outdrive you will be dragging in the water, and, in theory, more top speed.
Normally, to accomplish this, you would have to re-glass the transom, and cut a new hole (higher up on the transom) along with raising the engine mounts.
IMCO makes bolt-on lower units that raise the propshaft in 1" increments, so no need to change the engine location if you want to change the "X" dimension (for example, a 1" shorter lower unit means the propshaft moves up 1").
Having said that, they are expensive. Also, there are usually handling tradeoffs (such as prop blowout out of the hole and in hard turns), which can make for a not-so-fun boat to drive.
You may want to talk to someone who has done it first, before you spend the money.

[HP350SC]

Originally posted by Havasu Hangin'
I think you are talking about IMCO lower units?
For top end speed, the higher you can run the propshaft (relative to the bottom of the boat, or "X" dimension), the less outdrive you will be dragging in the water, and, in theory, more top speed.
Normally, to accomplish this, you would have to re-glass the transom, and cut a new hole (higher up on the transom) along with raising the engine mounts.
IMCO makes bolt-on lower units that raise the propshaft in 1" increments, so no need to change the engine location if you want to change the "X" dimension (for example, a 1" shorter lower unit means the propshaft moves up 1").
Having said that, they are expensive. Also, there are usually handling tradeoffs (such as prop blowout out of the hole and in hard turns), which can make for a not-so-fun boat to drive.
You may want to talk to someone who has done it first, before you spend the money.
Good advise HH.

[dorC]

The Baja is a production boat that is supposed to look fast. It is not to be confused with a high performance boat. By going to a shortened lower unit, you'll have less drag and higher speeds. A lower with some prop work will be good for around 5mph. You can find a used one for around 2k. Now remember, what I said above. Your boat will be ok into the very low 70's. After that you'll start exceeding the hull's capabilities and things will get dangerous. My advice-play with this boat for a while. Maybe do some performance modifications to it. When you get to the 70mph range, you need to start looking for a new boat. Just don't fall in love with it and get a engine built or something like that. You'll be wasting your money.

[playdeep]

dorC,
Excellent advice...A couple of my friends had Baja's and decided to Motor UP.The results were less than impressive.
One of the guys went from a 502efi (415hp) to a 540(600hp)and picked up less than 5 mph.
The Baja as a speed demon is just not gonna happen no matter how much H.P. you throw at it.
Big power in a 24ft. Hammer,you are still going to get waxed by boats with less horsepower.
I rode in a Hammer with a whipple charged 502,even with BIG trim tabs that thing was a handful....

[bajaboater502]

I will agree with you that baja is a production boat but who isn't unless your talking big money. Even fountains and hustlers are production boats. We have a baja 272 with a whipple running 6 psi of boost spinning a finished bravo one 30 pitch on a 2 inch shorter imco extreme drive running 84-88 mph on GPS. it ran 73 without the whipple. And if I put the 8 psi pulley on it it will run into the low 90's, Granted it is not 120 mph but to me that is fast compared to most boats we encounter. While a step hull would probably see more performance they also come with their own handling quirks. It had touchy handling until the hydraulic steering and now it is just fine, infact it handles just as well as my buddies 27 fountain. The beautiful part is I have a 454 mag that can go with this boat if I ever decide to part with it and my new whippled 500hp can go into what ever else I choose at that time.
As for the shorter drive I don't think it would show you much improvment in speed with your setup. I only gained about 1-2 mph from it before the whipple, and the hole shot and planing decreased in a major way until I switch from a hydromotive clever to a bravo 1 prop, now it is just about as good as it used to be. I would agree that you should enjoy this boat pretty much as it is and look for something else a year or two down the line. Not because it is a Baja but because of limited engine (without a full tear down) and because most hammer owners I know end up buying a larger baja within a few years because of its limited space. Anyway if the boat gets you to the party and you have fun with it then it is a good boat no matter what name is on it.
The general rule of thumb is 1 mph for every 17-20 hp you add, and I believe the Hammer is a 21 foot boat so big power might get a little tricky in rough water. Have Fun all see ya on the water.

[YOUNG]

Thanks for all the help. I agree that maybe I should just leave the lower unit alone and just add a few minor mods to the motor and just see what I get out of it. I do plan on in a couple of years to get a larger boat,hopefully a CAT. The boat however does get us to the party and we do have a blast in it. Thanks again for the replies.