MikeW

Ok, I have a few questions. I had posted awhile back that I was looking at a few boats and asked your opinions. Well I ended up buy a 1990 Checkmate Convincor 251 GTX with the Brovo and not the TRS. It has a low Hp (310) Merc. I had a 1999 Liberator 21’ Pickle fork tunnel jet boat with an 850 hp blown 509. I have since pulled the 509 and installed a 502 and sold the boat. My plane is to NA the blower motor and lower the HP and eventually get it into the new boat. Just how much HP will the out drive take stock? Or what mods are needed to make it live at say…500hp or 600hp?

Next I wanted a boat that would pull double duty for us. I want it small enough to run on the Chain o lake here in IL and be able to get out in the rough stuff on Lake Michigan. I have ridden in this model boat and now how well it does. I looked for a long time for one in the right shape and the right price. so on to my next question. It has a SS prop on it now but the chain is shallow. Is it better to run an aluminum prop in the shallow water rather than the SS. Is there a speed or HP that makes the Aluminum unsafe?
Thanks for you helpin advance.
Michael

RLW

It's not what the outdrive will take as much as how nice you are to it. I am sure there are people on this board who run 500,600 and 700 HP thru these things and don't have problems.
I have heard so many different numbers I am not sure what the real answer is.
Here are some numbers. Merc HP500, stock Bravo, 470HP.
I am sure someone else here will post some info for you.

formula31

No on the aluminum prop. The ss one will take a lot more abuse before bad things happen. Id get a spare prop and have the tools to change it with you. Ive chewed thru some amazing things with my mirages and they survived just fine. On the Bravo surviving, its a crap shoot. Some do really well and others have lots of problems. For sure get a good drive shower.

Cord

iTrader: (2)

You have a couple of options. You could keep your blower motor stock and go with a beefed up imco extreme or B max drive. Might actually be cheaper than rebuilding your engine and strengthening the bravo. You will also need to determine how much power the hull can take. If you choose to keep the blower motor, you'll be wanting hydraulic steering and offshore style mounts.

If you decided to redo the blower motor, then the stock bravo should take 500hp OK. 550hp if you are willing to risk breaking stuff and have a good set of oars. The Xr's are good for 600hp. Those numbers are subjective because they're really based off how you drive the boat.

That Checkmate isn't going to be the lightest boat out there. I also hope that you checked the bottom to see how straight it is. I'm thinking that you'll be better served by using the Imco extreme and setting the depth deep and then using the stock blower motor. You'll loose some speed with the deep drive, but the boat will handle and plane out better. Besides, you'll be going more than fast enough with the hp.

Cord

iTrader: (2)

As to the aluminum prop...I know that the river does get a tad shallow. But with the hp the you are putting down, you're going to be stuck with the stainless prop. You could try a cheapie round ear that you'll rebuild once or twice a year, then save a good one for the lake.

Pwrbt33

iTrader: (2)

Mike,
I did a short deck 540 for my friends 25 Convincor with a Bravo 1 drive and it held 750 hp for over 3 years and finally let go. He was easy out of the hole and real easy coming back in. He also only runs Mercury green drive oil with an additive from Pro blend products. With this much power apinning a 29 4 blade Spinelli the boat ran the best of 86 on gps. If you have any questions, feel free to email me.

Pwrbt33

MikeW

Thanks Guys. I dont want to maintenance of the ultra high performance motor any more. It ran 8.5:1 with 9 psi of boost. My plan is to sell off the blower and Dart 345 heads and go with Smaller Aluminums heads Sigle plane intake and 850 DP. The pistons where deep in the hole so i can deck the block and work the head to dring the CR up (along with a different cam). With Eagle H beem rods, Scat 4043 crank, and JE pistons, If wanted more I could slip in a healthy NOS shot here and there. I have done the triple digits thing and after the bad Karma that there was in boats and boat racing this past year, I just want a 65-75mph family boat. I would guess the 310hp should put this tank to 55-60 with a little help. 65-75 is not that far off.
MikeW

MikeW

Mike with Speed Performance over in Wauconda in the best in the area. 847-487-7223

I live off of Redhead lake like over by Freddie's We need to hook up out on the chain this year!