convincor 251
 

Good morning. I recently purchased a 1986 convincor 251. stepping up from a chris craft scorpion 230. Haven't had a chance to have it out on the water yet. In the process of putting engine in. I purchased it without a engine. I am putting in 450 hp 454 with factory ex manifolds with silent choice and 4.5" thru hulls. It has a alpha one out back. Not sure what prop to start out with. I have a ss 21 and a 23. From what I have researched about this boat it appears to be a pretty fast hull. Any info about handling or what to expect out of the boat would be greatly apprec. With that motor set up what should I expect for a top speed. Thanks in advance.

Congrats on your new purchase. Before you install the engine just remember it`s an alpha drive they don`t like to be abused easy on the take off and don`t go blasting thru waves with the prop coming of the water. I have one on my Formula with only 350hp 454 and I have had 300 plus hours of great use. If you budget can handle it look for a bravo drive. Look in the swap shop you will find some deals. Good luck with your project.

I would anticipate speeds in the mid 60's if your 454 is putting out 450hp. The Alpha drive is faster through the water than the Bravo but the Bravo will handle more abuse than the Alpha. Mercury did package the 454 Magnum (365hp) with the Alpha drive back in 1987/88. I'm running a Checkmate 2800SX outboard with twin Mercury 2.4L 200hp outboards and running 71+mph...similar hull bottom as your Mate..

Actually, in 1987 merc packaged a 330hp 454 and the alpha but had constant complaints of blown up drives which prompted the release of the bravo in 1988. The 365hp 454 mag was released along with the bravo in 1988. The base 454 was renamed 7.4 litre (rated at 330 hp) was released at that time.

so let me ask you guys this. On my 450 hp build I was going to use ported oval port bbc heads. I now have access to Brodix heads. They are alluminum with 2.25/1.88 valves. 300cc intake runners and 132 exhaust. I know there will be a huge weight savings, but I am concerned about losing to much bottom end with having such large intake runners. But I think I can compensate for that because I am using a predator carb set up for marine. Let me know what you think. The heads are practically being givin to me so I would like to use them.

In my opinion unfortunately the heads are going to be alittle too large for your application. There are a lot more knowledgeable people on here then me though. If you post in general forum about it you'll get more responses.

I know this post is a few years old. I'm rigging a 251 Convincor I bought. It came with a 30" Armstrong bracket, and supposedly left the factory uncut for an IO. I will be powering with Mercury 25" 2.4 225's. What props and gear cases did you run on your 2800? Thanks!

You may want to start a new post in the checkmate section to get some more responces. Not sure how many convincors we're rigged with outboards... But I'm sure someone here has a setup close to yours.

^^^ plus 1