Changeout of 3.0 to a 4.3 or 5.0 Mercruiser

[powrguy]

I'm looking at the cost/work involved in a changeout from a 3.0L Mercruiser (1988) to either a 4.3L or a 5.0L Mercruiser. I believe the outdrive would be the Alpha 1, and wonder if the changeout would involve lots of mod's to the outdrive, or would it be a bolt-up, and just a flywheel issue? (I suspect the upper gear ratio/prop issues would be another consideration?)

thanks

 

[Bondo]

Re: Changeout of 3.0 to a 4.3 or 5.0 Mercruiser

and wonder if the changeout would involve lots of mod's to the outdrive,

Ayuh,... Yes it Will...

 

[powrguy]

Re: Changeout of 3.0 to a 4.3 or 5.0 Mercruiser

Ayuh,... Yes it Will...

I take that to mean, yes; lots of mod's to hookup to the existing outdrive? In other words, would I be better off getting a replacement complete engine/outdrive combo, instead of just getting an engine to try to re-use the existing O/D?

The 3.0 in the boat is about 10 hours old, having been completely professionally gone through, and the outdrive has also been completely serviced/checked out. There's nothing wrong with the 3.0 setup, except that I'm concerned about 130hp in a 21 foot, 2200 pound boat!

 

[Shadow66]

Re: Changeout of 3.0 to a 4.3 or 5.0 Mercruiser

I take that to mean, yes; lots of mod's to hookup to the existing outdrive? In other words, would I be better off getting a replacement complete engine/outdrive combo, instead of just getting an engine to try to re-use the existing O/D?

The 3.0 in the boat is about 10 hours old, having been completely professionally gone through, and the outdrive has also been completely serviced/checked out. There's nothing wrong with the 3.0 setup, except that I'm concerned about 130hp in a 21 foot, 2200 pound boat!

Oh man, my boat is 2,200 lbs and it's an 18'. I have a 3.0 Merc Alpha 1 Gen 2 and it's fine. I have a Stingray Bowrider, not sure what yours is...but I do 45 mph with 4 people easy.

 

[powrguy]

Re: Changeout of 3.0 to a 4.3 or 5.0 Mercruiser

Oh man, my boat is 2,200 lbs and it's an 18'. I have a 3.0 Merc Alpha 1 Gen 2 and it's fine. I have a Stingray Bowrider, not sure what yours is...but I do 45 mph with 4 people easy.

I am surprised at that. The boat is a Lund 21 foot Baron, and empty weighs in at about 2200 pounds. I don't know the prop pitch, but I suspect that it would get 35mph with the 3.0, with a couple people on board and 30 gallons in the tank. I don't know if it could top 40mph with a prop change or not. Just seems that 120/130hp in a 21 footer is a little on the weak side. Maybe not. I had a 115hp on an Aquasport 222ccp years back, and I remember how underpowered THAT was. I could get only about 30-32mph, and that boat probably was in the 2200 pound class.

I found that the powertrain is an OMC/Cobra 3.0L, 120hp. I'm trying to decide if I even WANT the OMC, based on lots o' comments regarding parts scarcity.