Re: bayliner hotrod project, help w/ top speed!!
just a big of a problem with cam overlap is idle quality. One of the biggest problems with running an alpha drive behind a built engine is having to get the idle consistently below 600 rpms so you don't chip a gear when shifting into gear... a much bigger deal when you're pushing the limits of the drive.
Also, run good grear lube and change it often. I run redline shockproof heavy duty - MUCH better lube for hypoid gears and made to work very well at high temps. There's just about zero lube circulation in an alpha drive...
Your gear ration should work well.
I've not personally seen the problem with overheating one - except where I had a small water intrusion problem and burn an upper gearset up. I sometimes run hard for relatively long periods of time. I don't run any exhaust through the lower unit / drive.
merc exhauts manifolds are the major bottle neck in the exhaust system. You won't see much difference in power between through prop and through hull with stock manifolds. You also won't see the kind of numbers you did on the dyno with your merc manifolds on there - think at least as bad as old factory car manifolds... water jacketed exhaust is expensive, but necessary when you want to make more power. You can get the water further from the engine by adding extension in your risers, but not nearly enough to handle the reversion in the cam you have - although the idle quality issue makes this a moot point... A lot of guys here (including one running a marhia with a blown small block in it) that run larger cams start the engine after they put it in gear... (pushbutton bypass for the neutral safety switch under the dash I think is the way to do that right...)
the cam in my 383 is 226 / 236 (270 / 286)duration, a little more now with the higher ratio rocker arms on it and lashed a little tight. I do have aftermarket exhaust with long risers. I'm likely in the same hp range bomar is especially with the new afr heads.
The only way to be sure about reversion is to run it at idle for a while - IN THE WATER, and then pull a manifold to see if you've got water...
I've had it apart the past week or so. Spent much of today gettign things back together from swappign heads, changing motor mounts, drive and transom service, some interior work, putting engine back in, and adding a few other "minor" upgrades... I just painted the boat in the past few weeks... Good luck with your toy. Cheers!
