Engine Swap

Not that I plan on doing this soon.. but if its possible it may be in the cards.

I currently have a 3.0L Merc with an Alpha One. If I were interested, how much work would it be to drop in a 4.3L?

The boat had options for the 4.3L orginally, so I would assume it would be possible to mount it up with the current space limitations..

Anyone ever done it? Have some pics?

Thanks!

SB

Re: Engine Swap

A lot of times even when its and option they do not glass in the mounts to support all the different engines.

The 3.0 has a compleatly different front mount and they glass in a different support for it

It can be done but it would be a big ? as to the work for the front mounts


Tommays

Re: Engine Swap

I've had to repower a few boats from 3.0L to 4.3L. As tommays mentioned the mounts are different. They usually have the stringers installed, that is needed for whatever engine is there, but the pads for the engine mounts aren't there.
Other things you will have to do is change the exhaust tube on the transom shield to a Y, and change the gear ratio in the drive ........ No just changing props won't do it.
Depending on the year of the 3.0L, locating parts shouldn't be a big problem.

Re: Engine Swap

Thanks guy, just somethin I might consider in the future when I get this boat running in top shape and realize it doesn't have enough power (inevitable, I know)...

What can I say, I'm a glutton for punishment just like the rest of us..

Re: Engine Swap

something else to think about.....

if your going to go through the trouble of messing with stringers and engine mounts anyway......

try a 5.0 or 5.7. odly enough, the small block base V8,s are cheaper than the V6,s. the alpha drive will easily handle 200 to 250 hp also.

Re: Engine Swap

Resurrecting this thread..

To re-illustrate my situation:
I've got a '89 Sea Ray 180 with 3.0 Merc Alpha One. Boat and engine are in good shape and I'm just lookin for a little more power.
I've come across a pretty good deal on a 1991 boat with a Merc 4.3L and Alpha One. The boat is crapped out, but I am only interested in the driveline anyway.

The owner stated that "motor ran fine until the upper outdrive gear stripped". I haven't looked at the IPB for the housing, so I'm not exactly sure what this means. If the engine is okay, I don't think I'm concerned with the upper housing.

What I plan on doing is switching out the engines and related exhaust as Don noted. I would then use the upper housing from my current Alpha One and the lower unit from the newer Alpha One.

A couple of questions I was hoping to get answered:
1. The gear ratio is created in the lower unit, correct?

2. If I use the upper unit from my current Alpha One (1989) and the lower unit from the newer Alpha One (1991), will I be okay? The only difference I am aware of is the lack of an o-ring groove on the newer shaft design.

3. I know the upper drive shaft is different in the newer A1, but that should be irrelevant in my situation, right?

Although it rarely turns out this way, I think this would be a relatively easy conversion. Of course there will be things to pop up along the way, but I figure I can handle them if everything else is okay. Any other comments/suggestions?

Thanks,

SB

Re: Engine Swap

If the 91 is a Gen II drive then you cannot use your lower.

next, the gear ratio is set by the gearing in the upper half of the drive.

If the gears in the upper sheared off, where do you think all of the metal buts went. I would not use any portion of that drive.

Re: Engine Swap

Re: Engine Swap

Guess I shouldn't assume anything..

In that case, I can get the gears to change my current A1 to 1.81 gear ratio for about $200. How much work is it to change the gears and are any special tools needed?

EDIT: Decided to take a look at the IPB. 1.81 ratio is for 4.3 V6 right?

This is a bit beyond me at the moment, so I will have to do some reading up. Do I need to change the gearing in both the Upper and Lower? Or is the forward/reverse gearing in the lower not related to this? I'm assuming it is not related and is dependent upon the drive, not the engine. Oh wait, I was gonna quit assuming things.... damn.

Re: Engine Swap

The lower gearing is "fixed", it is the same for all engines.

There are several special tools required for changing gears in your drive. It would be cheaper to replace it. You can get a new one with warranty from SEI for like $600. you would still have your old one to sell and regain a good chunk of that. The 1.81 ratio is correct for a carbed 4.3.

The easiest approach (for a swap) would still be to locate complete running donor to swap everything from.

OR

sell what you have and get a boat with a v6 or v8 already. It will be cheaper in the long run.