Basic Sterndrive Configuration Questions

[76SeaRay]

Ok, so before I embark on buying parts. I need to make sure I know what I am looking for/at and don't make mistakes in buying... After feedback here, I plan to go with the Mercruiser 5.7L carbureted and the Alpha 1 Gen 2 as the budget won't allow going farther than that. I know a thing or two about engines (can rebuild chevy's all day long) but not on sterndrives. Please see if I have this right (my past boats have been sail or outboard)...

For the whole sterndrive assembly I assume this is the sequence. Inside the transom is the gymbal "ring", on the outside on the transom is the gymbal housing, followed by the gymbal assembly, then the upper drive assembly, then the lower drive assembly, and then the prop. Inside the stern is the "lift" hydraulic pump for the outdrive.

Are the gymbal ring, housing and assembly the same for Alpha Gen 1 and Gen 2? I assume it is different for the Bravo series. Are these parts the same for all engines, that is, V6 and V8. Is the lift pump assembly for the Gen 1 and Gen 2 the same?

I found the topic on indentification of Gen 1 and Gen 2 upper and lower drive assemblies so I think I know how to tell the difference there. From a drive train standpoint, it appears that the gears are different ratios but the housings and shafts are the same for different engines. I see a lot of listing for gear ratios. Are these gears set up in the upper drive unit, lower drive unit, or both? What would be the correct gear ratio for the 5.7L Mercruiser for this boat (22ft and 3600lbs)?

Are the throttle and shift cables and connectors the same for Gen 1 and Gen 2? Are they generally a standard length or do I need to get something from a similar length boat?

And lastly, what would be an appropriate prop for this set up given that most of my boating will be cruising lakes, nice speed but not a gas hog??

Thanks...

 

[Bt Doctur]

Alpha 1 to Alpha 1 and/or MC1
Alpha GEN II to Alpha GEN II ONLY
Trim pumps and cylinders are compatable
the 5.7 260 Hp uses the 1.50/1.47-1 gear ratio
Cables are standard unless you have the newest control box`s
14 x 19 or 13 3/4 x 21 More of being in the correct rpm band

 

[Scott Danforth]

all boats are gas hogs. they burn 0.4# of fuel per hp per hour. so depending on how much power you need, that is your burn rate

 

[76SeaRay]

Great, thanks. So, everything has to match from the gymbal ring inside all the way to the lower unit on the outside, Gen 1 to Gen 1, Gen 2 to Gen 2. Does that also include the bell housing on the engine or is it the same for Gen 1 and Gen 2?

 

[Bondo]

Ayuh,.... The Gimbel ring is outside the boat, part of the gimbel assembly,...

The Transom Assembly basically consists of, the exhaust y-pipe, 'n inner transom plate, Inside the hull,....
Outside the hull is the transom housin', the gimbel ring, 'n the gimbel housin' inside the gimbel ring,...

The upper unit of the sterndrive bolts to the gimbel housin',...
The lower unit of the outdrive bolts to the bottom of the upper unit,...

I just typed this out for somebody else, somewhere else, but it sure applies to you as well,...
If yer doin' a pulleys to prop re-power,... Don't buy it by the piece,...

If yer lookin' for a different driveline, pulleys to prop,...
The smartest way to go 'bout it is Not to buy pieces,....
You should be able to find a rotten hull boat, probably up into the '90s, with a Merc driveline, pretty darn cheap,....
'n ya get ALL the pieces, even the little bits that tend to cost a fortune,...

The Gen.II Alphas came out in '91,....
Bravos came out in '87 or '88,...

Whatever ya do, go with Chevy base power,...
Chrysler has been outa marine since the '60s as I said,...
Ford left the marine biz in the early- mid'90s,...

Mercs are so popular, they're a dime a dozen,...
Volvos much less so,...
Parts both new, 'n used are high, because there's less of 'em,....

'n stay away from anything that says OMC on it anywhere,...
They're Dead, 'n Defunct,... Few parts, 'n No help available,...

 

[tpenfield]

+1 to Bondo's advice in terms of buying a complete outdrive/ transom assembly rather than cobbling bits and pieces together.

Your question seems to infer that you might not be looking for a complete setup, which will only be a nightmare for anyone without years of specific knowledge.

Probably the same goes for the engine portion of the propulsion system.

 

[Scott06]

These guys sells fresh water tear outs, seem a pricey vs finding a Craigslist trashed boat, but not compared to piecing it together.

http://www.ebay.com/itm/MERCRUISER-...ash=item2ef73fea06:g:YuEAAOSw9mFWML4G&vxp=mtr

 

[76SeaRay]

Thanks for all the info. It's not that I necessarily am looking to piece one together, rather, that when going into a mechanical project I like to educate myself for two reasons. First, I like to do as much of the work as possible and second, making sure I am not getting taken on part purchases. That said, I have been searching a lot over the past week and unfortunately most of what's out there are pieces and parts. But, I won't be ready for an engine and drive for quite a while yet so unless I find an outrageous deal on complete subassemblies, I don't have to rush into anything.

Next up will be pulling the OMC short block out and cleaning the inside to see exactly what I have to work with to mount in a Mercruiser set up. By the way, I will be rebuilding my first automatic transmission this weekend so not afraid to tackle things I haven't done before.

 

[tpenfield]

I think the parts diagrams that are available online are good references to understand the parts and how they all go together.

 

[76SeaRay]

So, I have now seen Alpha One Gen One, Alpha One Gen Two, and Bravo. Alpha One Gen Two is desirable as well as Bravo, however, as I search more, I see Bravo and Bravo 3. I know the Bravo's are newer but what is the difference in them. Is there a 1, 2, and 3 or just Bravo and Bravo 3?? Someone suggested a 7.4L with Bravo 3 but does an Alpha Gen Two handle a 7.4L??

Thanks..

 

[Rick Stephens]

It is usually a piece of cake to find a cheap(ish) boat with the power package you want inside it. Craigslist is how I did it. In the end, it was just about a wash going from a 4 cylinder Alpha 1 to a V6 Alpha 1 Gen II. I sold everything from pulled 3.0L motor and sterndrive to parts boat trailer, hydraulic pump, seats and windshield. You take the time to look, there is just about anything for sale out there to your hearts desire. With the boat itself water logged, or otherwise damaged making it a great way to purchase the power and sterndrive.

I would recommend that anything over 300 HP be a Bravo of one sort or another. You start talking spendy as the drives are twice as much to start with. But they can handle the added torque that will break an Alpha drive. 7.4L belongs on a Bravo, IMHO. Early on Mercruiser shipped a 7.4 with a Alpha - it didn't always work out well.

 

[Bondo]

Someone suggested a 7.4L with Bravo 3 but does an Alpha Gen Two handle a 7.4L??

Ayuh,.... In a nutshell, the Alpha 1 switched to the Alpha Gen.II in '91,.....

Bravos came out in '88 I believe,....

The Alpha series is smaller, 'n lighter for SBCs, 'n smaller motors,...

The Bravos are for SBCs, 'n especially BBCs,...

The Bravo I is a single prop drive, the Bravo II is a single, but Massive prop drive,...
The Bravo III is a dual prop drive,....
The upper gear cases are the same, only the lower units are different 'tween 'em,...

 

[tpenfield]

Bravo outdrives are for the big boy boats. They are designed to take lots of power. Bravo 1 is for the go-fast boats . . . Bravo 2 is for the big cruisers . . . Bravo 3 has counter rotating props and is designed for day boats and cruisers.

 

[76SeaRay]

This 76 Sea Ray specs at 3,600 lbs. I assume that's dry weight. It has a 60 gal gas tank and 9 gallon water tank so guessing that loaded operational weight is upwards of 4,500 lbs. Is the Alpha One Gen 2 with a 5.7L going to be enough to push it around with good performance? Looking for the right combination to make sure I don't have any troubles with it and get good performance out of it. Also, if the 5.7L is enough is there any benefit to going to Bravo 1 with a 5.7L?

 

[Rick Stephens]

My very humble opinion, minimum 383 stroker motor on a Alpha1 with that much weight. It would be a much better responding boat with a 7.4 and a Bravo.

 

[76SeaRay]

Sounds like this boat is caught in the middle between 5.7L and Alpha One Gen 2 and 7.4L Bravo 1 in the power to weight ratio. The original engine was an OMC 351 Windsor which pretty well equates to the 5.7L in performance (I think as I know Chev engines but not much about Ford engines). I don't know what the original performance was like with the 351 though so can't quite make up my mind on which way to go. I assume the 383 stroker falls in that middle category. The 7.4L with Bravo 1 is expensive so not sure that is in the budget.

 

[76SeaRay]

Ok, so back to educating myself more. I haven't been able to find a full set up but want to get on with getting the transom rebuilt and the transom assembly installed since I can find transom assemblies out there. So need to know a bit more about interchangeability. I know I need a Bravo 1 for a 7.4L but may still go with a 5.7L so need to understand the Alpha's as well as the Bravo's.

Is there a difference between the Alpha 1 Gen 1 Transom assembly and the Alpha 1 Gen 2? That is, is the only difference between the Gen 1 and Gen 2 occur in the upper and lower outdrive units? so that I can get an Alpha 1 transom assembly without regard to Gen 1 or Gen 2? Most ads don't specify for the transom assemblies.

Would an Alpha 1 Gen 2 from a smaller engine and boat mate up and hold up to a 5.7L?

I understand the Bravo 1 transom assembly is different from the Alpha but is it the same for Bravo 1, 2 and 3?

Does in make much sense to go to a Bravo 1 if I use a 5.7L?

Thanks.

 

[HT32BSX115]

And lastly, what would be an appropriate prop for this set up given that most of my boating will be cruising lakes, nice speed but not a gas hog??

Thanks...

I think your boat is similar in size and weight to my 1987 FourWinns 211 Liberator.

I would find a 454 + Bravo III. My FourWinns (1.81:1 ratio + 24p props) cruises nicely at about 30 MPH burning 10 GPH, and has spectacular holeshot performance.

In 2006, I paid $5k for my 1997 (120hr since new) Mercruiser 7.4L + Bravo III drive (it all came out of a wind damaged 24ft Bayliner....
(I got everything including the harness and gages)

At the same time, I could have also bought a 2004, 300hp (400hrs) closed cooled, 5.7L MPI + Bravo I for $6500 ......... It probably would have been ok but I think the Bravo III runs much better in heavy boats. ............mine weighs 2900lbs without the engine..... the engine is 1200lbs more, for a total of about 4100lbs and with 44gal of gasoline about 280lbs more (+ people and dogs)

If you put a 5.7L engine in it, I would suggest a newer MPI engine (for the additional HP) plus a 2.00 or 2.20:1 Bravo III

All the Bravo drives will bolt to all the Bravo transoms

Cheers,


Rick

 

[Scott06]

Alpha Gen1 /Gen2 transom assemblies are different, not sure of all differences but there is a gear lube supply to the drive through it, the shift assembly and trim cylinder mounting I'd different.

There is no difference in the lower hp Alfa drives except gear ratio in the upper. A 5.7 will use a 1.47 ratio, 5.0-1.62, 4.3-1.82, 3.0-1.98. You can prop around the ratio to some extent. For example On my boat I repowered from a 4.3 to a 5.0, I kept the 1.82 ratio but had to go from a 19" to 21 or 23" prop. Had I put a 5.7 in it I don't think I would have been able to prop high enough to get around the drive. It's usually more cost effective to find a correct ratio drive than re gear.

Yes a

Bravo transom are the same. A bravo and 5.7 will be fine as long as gearing is correct. As mentioned there are operational advantages to a bravo 3 in a boat your size, but most likely cost you more. A bravo 2 isn't appropriate for your application, these are for large boats that need a huge prop diameter

As far as getting the transom redone all the drives use the same key hole, so being mindful the the x dimension you can redo the transom while still looking for a pulleys to prop drop in. You can also find a junk one for fit up while looking

 

[Scott Danforth]

You need to ask youself......how fast do you want to go and how you intend to use the boat.

A 5.7/alpha combo would be a high 40's WOT boat with an aprox 26mph cruise at 3200 rpm

A 6.2 (383)/ alpha combo would be low 50's WOT with about a 28 mph cruise at 3200 rpm

A stock pork chop motor and Bravo package will push the boat to high 50's or even low 60's.

A built BBC will get you faster.

All of the motors will burn approximately the same fuel under light throttle.