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Discussion Starter · #1 ·
is there anything that one can do to make an alpha (not gen II) stronger. I posted earlier that I would like to make about 350-400 ponies, it looks like the alpha will prevent me from doing this, I could go with a more moderate engine build, say 300 prop hp.

It is my understanding at this point the max hp ratings for the drives is prop hp, is that correct?

Also how much hp loss does the leg have? 20-30%?

I am new to stern drives, please advise.

Higgy
 

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IMHO it is the upper tower shaft bearing that is the weak link, improved oiling is a must do. The bearing now survives by the oil being pushed bu the upper gear set and the RPM's are what kills them (the upper tower bearing is tiny). A drive shower is a must and I have had extremely good luck with Amsoils 75-90 GL5 gearlube (I think it foams less).

Good luck...BTW I have put a few GMPP ZZ4 crate motors in front of early Alpha's and had no problems with the above mentioned mods....But that being said, we prop the hell out of them to keep the R's at or under 5K.

GT :)hand
 

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Discussion Starter · #3 ·
Ok, that is a great start.

What I understand you to say is, improve oiling, keep rmp down.

Cool everything.

Which shower do you like there are quite a few, some look better than others, but dressing is not performance.

I also hear you saying keep the wot at or below 4800.

What about power application? easy up through plane then wot?

Thanks for the input!!
 

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Ok, that is a great start.

What I understand you to say is, improve oiling, keep rmp down.

Cool everything.

Which shower do you like there are quite a few, some look better than others, but dressing is not performance.

I also hear you saying keep the wot at or below 4800.

What about power application? easy up through plane then wot?

Thanks for the input!!
We have seen them spun at 5000-5200 for short periods without issue, as far as out of the hole, I really don't think the holeshot is too big of a deal unless you're doing it over and over again, the prop slippage should keep from shearing parts off, heat is the main killer IMHO.

As far as showers go, we used to make ours from a Vee drive cav plate water pickup and a few AN fittings and some hose, the early Alphas have a cavity around the top gear housing and we plumbed the water to the left side of the area and out the right, simple but very effective.

Most of the showers are pretty much based on the same principle, the biggest difference is in how they pick up water pressure.

GT :)hand
 

· 21' Bahner Sport
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Ok, that is a great start.

What I understand you to say is, improve oiling, keep rmp down.

Cool everything.

Which shower do you like there are quite a few, some look better than others, but dressing is not performance.

I also hear you saying keep the wot at or below 4800.

What about power application? easy up through plane then wot?

Thanks for the input!!
GT Jets is right on the money, I am currently running approx 375HP to an MR drive (pre Alpha but looks just like an Alpha). An old timer that was an Engineer at Mercury told me the MR drive is a great drive, also the first Gen Alphas and you could put up to 400HP to it no problem, BUT keep good oil in it and keep it cool. I run a 21 prop on it most of the time as my "ski" prop but I also have a cupped 23 that I run on it . This winter I am building a 383 Stroker for it and I do plan on using my MR drive.

Good luck and have fun
 

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When I called Mercury on this subject I got a different story.I was told the #1 drive,MR,and Alpha can withstand high RPM up to 7000.
I was told not to put big props on them because the shafts could not take the torque.They cautioned me not to be hard on the drive out of the hole and not to get the boat out of the water at speed.Which by the way is the same with a bravo that has excessive HP.
As stated before using good gear oil and changing it every 25 hours will help considerably.
I have run in excess of 400 HP on merc one drives a couple times successfully. Currently I have a Spectra 20 turning a Revolution 21 that GPS at 64 mph.
The key is to be easy on the drive,keep it well lubricated and keep it cool.I have seen people blow drives with stock 260 motors because they drive them too hard same with Bravos.I also know people with 1000hp and Bravos that have been reliable for over 10 years.They run small props big rpms and never abuse them.
Now that I have said this I will probably scatter my drive next time at the lake.
 

· 21' Bahner Sport
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When I called Mercury on this subject I got a different story.I was told the #1 drive,MR,and Alpha can withstand high RPM up to 7000.
I was told not to put big props on them because the shafts could not take the torque.They cautioned me not to be hard on the drive out of the hole and not to get the boat out of the water at speed.Which by the way is the same with a bravo that has excessive HP.
As stated before using good gear oil and changing it every 25 hours will help considerably.
I have run in excess of 400 HP on merc one drives a couple times successfully. Currently I have a Spectra 20 turning a Revolution 21 that GPS at 64 mph.
The key is to be easy on the drive,keep it well lubricated and keep it cool.I have seen people blow drives with stock 260 motors because they drive them too hard same with Bravos.I also know people with 1000hp and Bravos that have been reliable for over 10 years.They run small props big rpms and never abuse them.
Now that I have said this I will probably scatter my drive next time at the lake.
How do you like that Revolution prop? I have been looking at an Enertia prop but I hear good things about the Revolution.
 

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It is similar to a Bravo.Good hole shot,very good mid range,great handling adequate top end.Out of 5 props tested on my boat nothing else came close to the overall performance of the Revolution.
Probably the best part is stabbing the throttle at 20/25 mph.The boat throws you back in the seat.If you didn't know it you would swear it had a big block.First time in chop I ripped the Bimini right off.My buddy and I laughed for five minutes.
 

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Discussion Starter · #9 ·
ok now I am starting to get some ideas.

I have been told by others that turning 5k or more will kill an engine, I know better than that, it will take some time off but not kill it.

The prop that you are talking about, what are the specs.

Thanks for helping, looking forward to learing as much as I can.

Thanks.
 

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ok now I am starting to get some ideas.

I have been told by others that turning 5k or more will kill an engine, I know better than that, it will take some time off but not kill it.

The prop that you are talking about, what are the specs.

Thanks for helping, looking forward to learing as much as I can.

Thanks.

You will have to look up the specs.on the Mercury web site.
Remember that props work differently from boat to boat.Any decent prop shop will let you try different props till you get it right.
Mercury has more R&D in props than anybody.They may be more expensive than others but you normally get what you pay for.A good propeller is the best bang for the buck purchase you will make in my opinion.
 

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Discussion Starter · #11 ·
There is no shop around here anywhere that will let you try/demo tweak. They are all, buy it and own it before you put it on.

It is very frustrating.:)st

I would even pay shipping back and forth to try some of the props one reads about.

Will get there in the end.
 

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Discussion Starter · #13 ·
I live in Idaho (Close to Burly) at about 4300 feet. I have a '87 21 foot Sea Ray Sorrento S21 with a merc 260 and alpha one.

When I got the boat it had a 21" prop 14.75 inch dia.

5.7 liter 260 hp
alpha one with a 1.5:1 ratio
al prop 21 pitch 4878122 A40L 21P (dia 13.75")
centerline 20'8"
beam 96"
dry wt 2820
gal full 40
WOT is listed as 4200 to 4800 RPM

Other info:
I live at 4300 feet
2 adults (well by years anyway) 2 kids

Tech info as I know it:
given approx 3% hp loss per 1000 feet 12% loss (approx 31 hp) 260-31=229 hp

As far as I know the carb has not been rejetted

I am getting a WOT of 3000 rpm, engine is running well.

I then put a 5.7 liter 260 hp
alpha one with a 1.5:1 ratio
al prop 21 pitch 4878122 A40L 21P (dia 13.75")
centerline 20'8"
beam 96"
dry wt 2820
gal full 40
WOT is listed as 4200 to 4800 RPM

Other info:
I live at 4300 feet
2 adults (well by years anyway) 2 kids

Tech info as I know it:
given approx 3% hp loss per 1000 feet 12% loss (approx 31 hp) 260-31=229 hp

As far as I know the carb has not been rejetted

I am getting a WOT of 33-3400 rpm, engine is running well.

I put on a 15" dia 17 pitch prop.

on plane in 3 to 4 seconds and 50 or so feet.

Top speed 44 miles per hour
5000 RPM.

Most likely could have done a 19 prop but the hole shot would not have been as good.

I would like to get the exact prop in SS either a 3 or 4 blade.

Thanks
 

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It all depends how you beat on it.. Stuffing the throttle out of the hole will kill it !

Ease in and out of the throttle, pick and choose your water and it SHOULD have a nice long life span.

There is a guy who lives on my lake... has a mid 80's 21 ft Baja, Nasty sbc with an alpha, Im going to guess its around 400hp, and he beats that thing to death.. parasails, jumping wakes at 75+ without lifting, runs over sloppy water chine walking WOT. he hasnt rebuilt the drive in over 8 years.
 

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My Dads 23' sleekcraft is running an Alpha 1 behind his blown 350. He has broke gears before but he found some hardened gears for it and went with a little more mild prop. Has been working pretty good for quite a while now he does stay on top of maint. though.
 

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I routinely turn my alpha drive to 5500 or even a little more some days, sometimes for more than a minute or two... as in for 10+ miles. With a 383 making 400+ horsepower.

A well known performance marine engine / boat builder locally (Outstanding shop, did my current 383) told me that the alpha drive would be fine as long as I didn't hammer it out of the hole. He also told me that as long as you run good lube the temp is not an issue, that it needs to run hot to circulate better - they routinely remove the drive showers from the customer boats that come through their shop.

Note that I have a spare drive and probably enough good parts to build yet another.

big deal is taking care of it, not shifting at high rpms (if too much cam, start in gear), can chip a gear putting it into gear and then comes apart later. good synthetic lube, change / check frequently, if you get airborne, get out of the throttle(s) before the prop catches again.

the lower drive shaft is a weak spot. They shear off right at the o-ring groove below the splines.

I actually have an SEI lower (driveshaft issue above) under a merc upper drive on the boat right now.
 

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I routinely turn my alpha drive to 5500 or even a little more some days, sometimes for more than a minute or two... as in for 10+ miles. With a 383 making 400+ horsepower.

A well known performance marine engine / boat builder locally (Outstanding shop, did my current 383) told me that the alpha drive would be fine as long as I didn't hammer it out of the hole. He also told me that as long as you run good lube the temp is not an issue, that it needs to run hot to circulate better - they routinely remove the drive showers from the customer boats that come through their shop.

Note that I have a spare drive and probably enough good parts to build yet another.

big deal is taking care of it, not shifting at high rpms (if too much cam, start in gear), can chip a gear putting it into gear and then comes apart later. good synthetic lube, change / check frequently, if you get airborne, get out of the throttle(s) before the prop catches again.

the lower drive shaft is a weak spot. They shear off right at the o-ring groove below the splines.

I actually have an SEI lower (driveshaft issue above) under a merc upper drive on the boat right now.
I have to agree to disagree on the heat thing..I have seen properly set up Alpha drives literally burn the paint off the top of the upper GC.
With some real simple porting on the oil holes in the upper, oil rotation can be improved so it does not foam the oil, which is what kills the upper bearings eventually killing the upper gearsets.

The later Alphas have no o-ring grooves on the tower shaft ;)

You can pick up an OMC shift interrupt module from the older OMC stringer motors (must match number of cylinders, V8, V6 etc...) and use them on the Mercruiser using the same studder switch on the Merc shift plate if using a tall camshaft, it cuts out every other cylinder in the firing order when activated.....Works bitchen...:)devil

GT :)hand
 

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Discussion Starter · #19 ·
Thanks folks,

I am going to pull the motor this winter and drop this 383 in. I understand that the older 270 like I have is rated at the flywheel and not the prop and is more like a modern 230.

It is my understanding that the 300 hp number that the alph 1 will take is at the prop, giving me some room.

Time to start selecting all of the parts.

When I get a build sheet togther I will post it and seee what you all think.

Thanks
 
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