new drive? bravo or alpha

[Frankiea87]

hey guys i have a 1988 Sundancer 268 with a 454 merc and an alpha one drive with 4 blade prop... i feel as if i should be getting a lot more speed than i am right now.. i cruise 28ish with just myself and half tank of gas. last year i blew my lower end on the drive and mechanic says this boat should have a bravo drive on it.. can i just unbolt the alpha and slap the bravo drive on? or is it more involved then that? or should i rebuild the carb first? different prop? other people with boats exactly like mine say they get almost 40mph out of them.. that would be AWESOME!!!

 

[Lazy Daze]

What's your WOT RPM? What's the condition of the prop and the hull bottom? Is the Alpha still blown or is it working order?

 

[Ididntdoit]

Top speed wise a bravo will slow you down (more drag) you do it for the strength or in the case of a II or III more bite. a stock alpha behind a big block in a heavy boat needs to be babied out of the hole to live any amount of time. You can't just throw on a Bravo as you would have to change the entire transom assembly and enlarge the cut out. If your motor is running up to spec I would try experimenting with stainless props to get the proper balance of holeshot/speed - by all means don't try to push anymore power through that alpha!

 

[Quint4]

Get a Bravo it's a much better match for your engine. No, you can't just bolt it on.

 

[Frankiea87]

yea my WOT RPM is almost 5k... but i just feel i should be getting more out of it.. should i try the rebuild of the carb and maybe itll give it more power?

 

[Lazy Daze]

If you're getting 5K, you've got the power. Could be that the prop is wrong (pitch is too low).

But.... Is that 28MPH according to your dash speedo? Double check it with a GPS.

EDIT: Let me restate the above... you are definitely running a prop that is pitched too low. Someone correct me here, but I think the MAX WOT for your year 454 is around 4500?

 

[Frankiea87]

yea i use my GPS from my fish/depth finder... also i believe the prop is 14.5 x 17 ...

 

[Lazy Daze]

One other variable that we should eliminate is Tach error. Ideally, swap it with a known good one. But, first try this: On the back of the tach is likely a little switch that can be, well... switched to either 4cyl, 6cyl or 8cyl. Exercise the switch back and forth a few times and then make sure it is left in the 8cyl position. Let's see if it's still reading 5K after that.

 

[Lazy Daze]

Oh, one other thing... Has the boat always acted like this... or just since the new foot?

 

[MonacoMike]

Strange coincidence that just about the time of your post I was looking at anothercustomers 268 7.4 w/A1 and my service guys were talking about how the drive didn’tlike the power of the big block and they had a history of failing. They definitely recommend a Bravo???. MM

 

[keokie]

The Bravo won't slow you down in this application. The efficiency of the smaller gear case of the alpha is offset by the taller gear ratio the used with alphas and 454's. I've done the switch. A BIII will give you much better performance throughout the rpm range with no sacrifice in top speed.

A 268 with a good running 454 and BIII will get you in the low to mid 40's.

You have to pull the engine and change the transom assembly to convert to a bravo.

 

[jamesgang]

I had an '88 Sorrento 250 with the same set-up (original white outdrive), blew that one up and another before I learned that the 454 has too much torque for the alpha drive. Sea Ray only paired them for a couple of years. It's true that you should baby it out of the hole. If I'd known that . well, too late now. Sorry I don't remember the tach #'s but she was a sharp-looking boat. Guy I sold her to ran over a barge rope and messed up the new O/D I had put on.

 

[Tail Chaser 661]

Alpha 1 to Bravo drive.
New Bravo transom assembly. Steering ram. Drill two more holes in transom for the Bravo assembly.
cutout is the same. Maybe a new trim pump for the heavy drive? I switched mine out.