Heavy Alpha One????

[Windykid]

Is it possible to convert or rebuilt an Alpha one to handle a big block motor?

 

[Haut Medoc]

Re: Heavy Alpha One????

You could put 1.32 gears in it, but Merc only put the BBC's in front of Alpha for a year or two because they won't hold up.....
The Alpha is only rated to 300 HP.....
You can get a Vortec that will get close to that.....
If you want a big block, get a boat with one & a Bravo drive....​

 

[Windykid]

Re: Heavy Alpha One????

Problem is I bought a 1985 Chris Craft Scorpion 230. The PO swapped out the 350 for a 454. I havent had a problem yet but I am wondering if it is going to hold. Also nedd to test speed by GPS because it is running 4100 RPM at WOT, The speedometer reads 50 MPH. You would think that it would run atleast 65. It could be proped wrong?

 

[Windykid]

Re: Heavy Alpha One????

Also how do I check for the 1.32 gear?

 

[paulrfrancisco]

Re: Heavy Alpha One????

Sounds propped wrong, rpms should be closer to 4400-4600 on the 454ci, also 1.32 ratio can be checked either by looking up the serial number and posting to this board, or the manual way, by marking a point on the prop and on the harmonic balance (maybe use a large socket wrench while the engine is off and turn it to the 0 degree timing mark...) then mark the prop at the top with a marker. Next, you need another person, put it in fwd gear, and using the large socket wrench, turn the motor unlit the prop turn around back to the top again. No note when the timing mark is. It would be about 1/3 more than one full turn aroun on the crank to be 1.32:1 ratio. if its 1/2 more than one full turn, then is a 1.5:1 ratio... etc, etc... this is best done out of the water...

 

[Windykid]

Re: Heavy Alpha One????

Thanks paul. The serial number will probably tell what used to be there, according to the PO the out drive has been modified.

 

[SuperNova]

Re: Heavy Alpha One????

There are actually two different sets of 1.5/1 gears. One is the normal duty for small-block v-8's and the other is a heavy duty version for big-block v-8s. An alpha with the correct upper gearset in it will hold out fine behind a big-block. Others will contradict me, but this is a case of "been there done that".

 

[HT32BSX115]

Re: Heavy Alpha One????

Don't believe your performance numbers until you verify with GPS and a known tach. Tachometers can easily be up to 500 rpm off at the high end.

With big block you are pretty much at the higher end of the capability of an Alpha.

Mercury changed to the Bravo for a reason. Yours probably will "hold" as long as you don't "Straight Arm" the throttle a lot and you do not do a lot of WOT running. (why have a BBC in it then?)

Your other choice could be to run it until it blows and replace the whole mess with a Bravo I or III (I would vote for the III) Of course if you do that you won't have much to resell....

My Best choice (if just cannot turn loose of the boat) would be to pick up a used Bravo drive/transom/raw pump etc, and swap it out and sell the alpha stuff. There's always someone needing an Alpha.


By the way once you know the "numbers" you can use a Prop Slip Calculator to determine where you are with performance. You need acurrate speed and RPM though for it to be useful.


Cheers,


Rick

 

[Windykid]

Re: Heavy Alpha One????

Super Nova is there any way to check that? Also anyone have a thought about the WOT speed?

 

[Windykid]

Re: Heavy Alpha One????

Don't believe your performance numbers until you verify with GPS and a known tach. Tachometers can easily be up to 500 rpm off at the high end.

With big block you are pretty much at the higher end of the capability of an Alpha.

Mercury changed to the Bravo for a reason. Yours probably will "hold" as long as you don't "Straight Arm" the throttle a lot and you do not do a lot of WOT running. (why have a BBC in it then?)

Your other choice could be to run it until it blows and replace the whole mess with a Bravo I or III (I would vote for the III) Of course if you do that you won't have much to resell....

My Best choice (if just cannot turn loose of the boat) would be to pick up a used Bravo drive/transom/raw pump etc, and swap it out and sell the alpha stuff. There's always someone needing an Alpha.

I will look in to that, Thanks!

 

[SuperNova]

Re: Heavy Alpha One????

Super Nova is there any way to check that? Also anyone have a thought about the WOT speed?

You have to remove the drive, remove the cap and the input shaft, then you can get the gears out and you have to look at the shoulder on the gears, the heavy duty units are much thicker than the regular versions and use a thinner roller bearing. It sounds more difficult than it actually is to do. If you are at all mechanically inclined you can do it. But without a set of gears to reference I don't know if you'll recognize the difference. I have a set of the regular-duty gears laying around here somewhere. If I can find them I'll measure them for you and post. Other than that there is no way to know. The 1.32's would be a mistake I think and you may have a set in there which would be why you can't hit your rpm window. With a 21 pitch prop on there and 1.5's you should hit 5000 rpm easily unless the boat is waterlogged or soemthing is wrong with the engine.

 

[Windykid]

Re: Heavy Alpha One????

You have to remove the drive, remove the cap and the input shaft, then you can get the gears out and you have to look at the shoulder on the gears, the heavy duty units are much thicker than the regular versions and use a thinner roller bearing. It sounds more difficult than it actually is to do. If you are at all mechanically inclined you can do it. But without a set of gears to reference I don't know if you'll recognize the difference. I have a set of the regular-duty gears laying around here somewhere. If I can find them I'll measure them for you and post. Other than that there is no way to know. The 1.32's would be a mistake I think and you may have a set in there which would be why you can't hit your rpm window. With a 21 pitch prop on there and 1.5's you should hit 5000 rpm easily unless the boat is waterlogged or soemthing is wrong with the engine.

Thanks again, I think that it is proped wrong. I think it has a 23 on it. I will check this week and get back to you.

Also am very mechanicaly inclined, was a diesel tech for 20 years. I just dont know &^^%$% about outdrives

 

[180shabah]

Re: Heavy Alpha One????

Also anyone have a thought about the WOT speed?

Top speed is a function of HP not cubic inches. All we know is that you have a BBC. How much power is it actually making?

 

[Windykid]

Re: Heavy Alpha One????

I believe the 454 min HP is 330, But I am probably wrong about that>

 

[45Auto]

Re: Heavy Alpha One????

Mid 50's is probably about the best you're going to see on a 23' Chris Craft with a stock 454.

The Stingray website has a big list of boats and test data, they show 54.9 MPH for a Chris Craft 230 Limited with a 454, and 46 MPH for a Chris Craft Scorpion with a 454.

http://www.stingrayboats.com/produc...fuel=OFF&showstingray=0&onetokeep=&tocompare=

 

[jaxnjil]

Re: Heavy Alpha One????

I believe the 454 min HP is 330, But I am probably wrong about that>

WK;thats what our 7.4 is rated at,330 hp.
here is the part # for the 1.50 heavy duty gear set 1841OA4

 

[Windykid]

Re: Heavy Alpha One????

Thanks for all the info!

 

[1976SRV190]

Re: Heavy Alpha One????

SHoot, if you want to see 65mph out of that hull, you'll need a blower on that 454......realistically 55 is tops with that setup for sure. My little Sea Ray SRV 190 pulls only about 51mph at 4550rpm with a 888/888 combo.

 

[chaddemler1980]

Re: Heavy Alpha One????

i have an alpah for a big block... i need one for my 350, u interested in a trade? mine is fine and came off a working unit.