Are 7.4 L engines too much for Alpha drives?

[heatz1express]

Considering purchase of boat with twin 454 7.4L engines. the drives are Mercruiser Alpha drives. My question is, are the engines going to tear up the drives? I have been advised, by both a surveyor and a marine mechanic, to walk away for this reason. I don't want to!!! Really like the boat. Any input would be appreciated.

 

[Bt Doctur]

Re: Are 7.4 L engines too much for Alpha drives?

you dont list the boat size but generally Alpha`s will tolerate up to 300 hp. big blocks 330hp need a very gentle throttle hand.
Twin bravo`s would be a better choice.

 

[heatz1express]

Re: Are 7.4 L engines too much for Alpha drives?

you dont list the boat size but generally Alpha`s will tolerate up to 300 hp. big blocks 330hp need a very gentle throttle hand.
Twin bravo`s would be a better choice.

The question is...are the Alpha's a deal breaker??? I think I could learn to have a gentle throttle hand, maybe!
the boat is a 34 foot Baja Express

 

[thumpar]

Re: Are 7.4 L engines too much for Alpha drives?

Mercruiser did it but for only 1 year IIRC. They can't handle the power. If you like the boat just plan on changing the drives to bravos and factor that into the cost.

 

[MarkSee]

Re: Are 7.4 L engines too much for Alpha drives?

In my opinion not a deal breaker if you really like the boat and be overly good about maintenance especially gear lube which is a no-brainer.

I'm not a hp/torque graphing kind of person but isn't it possible to get a spec with those motors on what rpm peak horsepower is reached which doesn't hp build UP TO that rpm? Then if you stay below that rpm if say the engine put out 330 you fine.

Let me say though that on my 2000 model 7.4 it is stated 310 hp, not 330. Which then means you are just barely over max rated.

Maybe depends on the model in the boat you're looking at.


Mark

 

[heatz1express]

Re: Are 7.4 L engines too much for Alpha drives?

Mercruiser did it but for only 1 year IIRC. They can't handle the power. If you like the boat just plan on changing the drives to bravos and factor that into the cost.

Wondered about that. Any idea how much trouble it would be and how much it would cost?

 

[MarkSee]

Re: Are 7.4 L engines too much for Alpha drives?

Wondered about that. Any idea how much trouble it would be and how much it would cost?

I'm not going to begin to know ALL the parts needed especially if a different computer module is needed but if you really want someone to try and answer that question, you probably at least should specify if you are considering a Bravo1 or Bravo3 and new or used.
In case you don't know, new Bravo units just by themselves are around $6k....each with shipping:
http://www.michiganmotorz.com/mercruiser-bravo-outdrive-p-444.html
http://www.michiganmotorz.com/mercruiser-bravo-three-outdrive-p-344.html

Certified pre-owned won't save much:
http://www.michiganmotorz.com/mercruiser-bravo-outdrive-p-937.html
http://www.michiganmotorz.com/mercruiser-bravo-three-outdrive-p-3582.html

Mark

 

[Don S]

Re: Are 7.4 L engines too much for Alpha drives?

Wondered about that. Any idea how much trouble it would be and how much it would cost?

You change everything but the engine.

 

[HT32BSX115]

Re: Are 7.4 L engines too much for Alpha drives?

Let me say though that on my 2000 model 7.4 it is stated 310 hp, not 330. Which then means you are just barely over max rated.

That is the propshaft HP. Back in 87 the 7.4L + Alphas were rated at 330 crankshaft HP........(which loosely relates to approx 300 propshaft HP......my carbureted 1997 7.4L + Bravo III is rated by Mercury at 300 prop-HP)

Mercruiser rolled out the Bravo the following year (88)...and they did it for a reason........ A 7.4L engine won't always break an Alpha and there's plenty of people here and elsewhere that have them and have not had a problem.

I have been advised, by both a surveyor and a marine mechanic, to walk away

Yeah. That's the "conventional wisdom" because a fair number of Alphas have been "broken" by the BBC.

Nowadays, Mercruiser doesn't offer the BB or the 383 (or any engine over 300hp) with the Alphas The newest Alpha might be "ok" with a 454. But I'll bet there's *some* improvement with the newest Alphas over 20 year old Alphas.....

This isn't a Fourwinns 261 Liberator is it? A LOT of them got twin Mercruiser 454/Alphas and twin 460 (340 crankshaft HP) King Kobras

You get away with no problems...........I would plan for a drive replacement budget though....

Wondered about that. Any idea how much trouble it would be and how much it would cost?

Understand that you change both the drives AND the transom mounts. A new Bravo transom mount costs anywhere from $2500-3500. I have seen used ones on ebay for around 500-1000. etc.....

A complete drive and gimbal mount change from Alpha to Bravo would cost a small fortune!


ymmv


Rick

 

[tazrig]

Re: Are 7.4 L engines too much for Alpha drives?

Big blocks with Alpha's just equal trouble. Why start off with a problem. The overall HP and particularly the torque will eventually shred the drive. That is why Mercruiser no longer puts them together or supports them. I just Re-powered with 300hp and that was as high as Merc would support. As far as your case being a deal breaker? Absolutely. It's no different then if you bought that boat that was soggy. Would it run today? Sure. Would it run tomorrow? Maybe. But eventually you are going to have problems. Why start off with something you KNOW is going to give you a problem? Unless it's worth you buying knowing you're going to have to replace "everything but the engine" as Don put it, just walk away. There are plenty of others out there.

 

[tpenfield]

Re: Are 7.4 L engines too much for Alpha drives?

I think the mechanic and surveyor are giving you proper advice. As stated, it is an incompatibility problem that existed for a year back in the day just before the Bravo was released.

The question is, if the Alphas are original (then it would be a 1987 boat ?) or if Alphas were put on more recently rather than replacing the outdrives with Bravos. The torque of the 7.4L will most likely shorten the life of the Alpha drives and the cost to put Bravos on would be $10K+. Additionally, you do not know how those Alphas have been treated up until now; did the previous owner(s) use a light handed throttle :noidea:

So, it is a liability that you are buying and perhaps not worth it, considering that there may be plenty of mid-30 foot boats to choose from.

 

[HT32BSX115]

Re: Are 7.4 L engines too much for Alpha drives?

Additionally, you do not know how those Alphas have been treated up until now; did the previous owner(s) use a light handed throttle :noidea:

I'm with you Ted! The first thing I want to do is "NAIL" the throttle!