Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

[JoLin]

I'm looking at a 26 footer with the above I/O mated to a Mercruiser 5.7 Liter carbed Chevy. The outdrive was fully rebuilt a couple of years ago. The owner told me that other than the annual fluid change, the only thing he keeps a close eye on is the waterpump, as this model has a small impeller. Says he changes it every year, also. Otherwise, he says, they work fine.

What's the general consensus? Are these okay units? Do they have any inherent weaknesses I'd be smart to know about?

 

[JustJason]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

nope.... other than the size of the boat it may be a bit underpowered. The power package is about as good at they get. But by all means.... have the boat surveyed by a mechanic before you buy it. See if the owner will split the cost of the survey.

 

[TilliamWe]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

Jolin, I wonder what the owner thinks of the impeller in an Alpha One (gen 1)? The impeller in an Alpha One Gen 2 is larger and much more durable than in the old MR and Alpha drives. But whatever.

An Alpha One Gen 2 drive behind a carbureted 5.7 is not an issue at all. Except that it's in a 26' boat! Depending on a lot of factors, that carbed 5.7 at 250hp might be working awfully hard to move a 26' boat.
Why did the drive need to be rebuilt in the first place? But even if the boat is a "drive killer", brand new SEI drives are $1395, with a 3 year no fault warranty. Just consider that in your purchase price.

 

[JoLin]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

Thanks, guys-

the boat is a 1986 Four Winns, which is a somewhat "upscale" boat. Mfr says it weighs 5000 lbs. The owner is an auto mechanic and says the motor is mildly modified- pumping around 300 horses instead of the stock 260. He also has a SS prop on it that was sized and modified (cupped) by a well-known outfit in the area. Finally, there's a set of hydraulic tabs on it.

According to him, the boat jumps right up on plane, cruises at 23 knots @ 3300 rpm @ 8 gph and tops out at around 40 knots. Do those numbers seem reasonable?

I don't think the boat is necessarily a drive killer. It's just more than 20 years old, and he's only owned it for the last 4 years. The rest of the boat is very clean and seems to have been well taken care of. I'll be making some calls tonite to find someone in the area that can check it out for me

 

[jaxnjil]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

According to him, the boat jumps right up on plane, cruises at 23 knots @ 3300 rpm @ 8 gph and tops out at around 40 knots. Do those numbers seem reasonabl


every thing but the gal per hour for fuel. that sounds more like 5 to 7 mphs flows.
i wouldnt bank on more that 3mpg and thats with fingers crossed on a ideal day.

 

[JoLin]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

His gph figure sounded optimistic to me, too, but I wanted to get a feel for what folks here would consider a reasonable figure.

Even if actual consumption is more like 10 gph at cruise, that's real close to the "mileage" I get from my 21' with 175 hp Johnson on the back. I'd be pleased- this is a lot more boat.

 

[chiefalen]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

I tell you what go for a ride with the person.

Make sure it is full of gas.

Bring your gps go out and find out how fast, how mush gas, and at what rpm, it really runs.

When you come back in make sure you record exatly how long you ran it for and how mush gas it burned bye filling it back to the rim again.

 

[TilliamWe]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

Thanks, guys-

the boat is a 1986 Four Winns...

Okay, first, unless someone changed the entire transom assembly and drive, that is NOT a Gen 2. That is just a plain old Alpha One. And it does have a "smallish" impeller. Not a piece of junk by any means, but not as good as the impellers in an Alpha One Gen 2. Oh, and to replace that drive with an SEI drive (brand new 3 year no fault warranty) is just $1195.

http://www.marinesurvey.org

 

[lkbum]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

A very good rule of thumb for 4 cycle I/O's for determining GPH is to multiply the Horse Power being used by 0.1 which will yield the GPH's. For instance, wide open using 300 HP would give yo a fule burn of 30 gallons per hour. At half power (not necessarily half throttle or half RPM) would yield 15 GPH. The numbers he quoted would yield about 3.3 MPG, this seems high, but for a lightly loaded boat on a "cool" day are not out of the question.

 

[JoLin]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

TilliamWe-

Know what? I think I misremebered that part of my conversation with the guy. I think now that he told me it was am Alpha 1 "Gen 1" and he changes the impeller annually because it's much smaller than a Gen 2. Darn it- sorry about that.

But the older Alpha 1 design is okay otherwise?

 

[TilliamWe]

Re: Mercruiser Alpha 1 / Gen 2 and 5.7 Liter Opinions?

TilliamWe-

Know what? I think I misremebered that part of my conversation with the guy. I think now that he told me it was am Alpha 1 "Gen 1" and he changes the impeller annually because it's much smaller than a Gen 2. Darn it- sorry about that.

But the older Alpha 1 design is okay otherwise?

Every year is overkill, unless you boat in really muddy/sandy water.

And yes, the design is the same in an Alpha One as it is in a Gen 2. The Gen 2 has bigger/stronger gears and that impeller. But nothing inherently wrong with an Alpha One.