Which Engine Should I Use?

[slowpropeller]

I have a 1967 Tollycraft Express. It currently has a 225 or 235 OMC. The engine is a 305. I plan on repowering it and changing to a Mercruiser Alpha One outdrive. After reglassing the old hole and cutting a new one, I am wondering If I should use a 4.3 L V6 or stay with the 305? The boat is 24', 8' beam, and weighs just under 4,000 lbs. Will I lose power and speed with the 4.3, or will power trim and lighter engine make up for the difference with the 305?

 

[achris]

Re: Which Engine Should I Use?

Hello Slowpropeller, and :welcome: to iBoats.

I can only tell you my experience. I have a friend who had a 305 (230hp) in a 23' Cuddy cabin boat (a lot more than 4,000#). We put my old 4.3LX (180 propshaft HP) in... He's 6 knots QUICKER and using way less fuel....

Whenever given the choice of a 305 or the 4.3, take the 4.3 every day!

Chris.......

 

[Fun Times]

Re: Which Engine Should I Use?

Hello Slowpropeller, and :welcome: to iBoats.

I can only tell you my experience. I have a friend who had a 305 (230hp) in a 23' Cuddy cabin boat (a lot more than 4,000#). We put my old 4.3LX (180 propshaft HP) in... He's 6 knots QUICKER and using way less fuel....

Whenever given the choice of a 305 or the 4.3, take the 4.3 every day!

Chris.......

Interesting, but I guess I can see it, bigger is not always better like one would think. What part of this did the gear ratio between the two engine sizes play in helping move the boat faster?

Also it seems this conversation will have to be moved over to the Non-Repair I/O and Inboards Discussions not involving troubles or repair section.

 

[duped]

Re: Which Engine Should I Use?

I'd go 350 if anything. Your boat...but especially at resale time, you'll have a tough time convincing people the V6 is better than a V8 in a 24ft boat... Not saying 4.3s aren't strong engines, but I think most people would consider that a bit underpowered. When my 305 went, I moved up. But in my time spent with the 305 (230 4 barrel) I also found that it was not at all the turd they are made out to be, so if yours is in good condition...cheaper to keep her. If it blows up down the road, all the merc parts you buy for it to swap will bolt to a 350.

 

[achris]

Re: Which Engine Should I Use?

... What part of this did the gear ratio between the two engine sizes play in helping move the boat faster?

I was as surprised as everybody else. The drive ratio for the 305 was 1.65:1, and the ratio for the 4.3 is 1.84:1, but both engines were propped correctly. In my boat the 4.3LX was running a 21" prop (and still going just over the top), so when we went for the water test with it in the 23' I put a 17" prop on, and luckily throw a 19" in the car just in case. Well, with the 17" it was like a startled gazelle! Up on the plan in a blink, but pulled way too many revs at the top end. Put the 19" on and it's still easy up and pulls 4900.... We're happy with it there. .....

Chris.........
Oh, and thanks for moving the threads around. There's one over in the Merc outboards. Title is '1993 Mercury 120hp Outboard - What Lower Unit Oil/Lube to Use?'... It's an Evinrude :facepalm:.... Any chance of a move to the OMC outboard board? Cheers...

 

[achris]

Re: Which Engine Should I Use?

.... it was not at all the turd they are made out to be, ....

Nobody's saying it's a turd... Just that there are better options...

 

[Fun Times]

Re: Which Engine Should I Use?

Oh, and thanks for moving the threads around. There's one over in the Merc outboards. Title is '1993 Mercury 120hp Outboard - What Lower Unit Oil/Lube to Use?'... It's an Evinrude :facepalm:.... Any chance of a move to the OMC outboard board? Cheers...

Handled, Thanks for the notice.

 

[duped]

Re: Which Engine Should I Use?

I was as surprised as everybody else. The drive ratio for the 305 was 1.65:1....

4 barrel 305 (230) should have a 1.50. I suppose if both motors were propped correctly it does not matter. Still quite a surprising difference with the swap nonetheless!

Wont disagree that there are better options than a 305, but also not fully convinced a 4.3 can fill it's shoes in 100% of the applications out there.

 

[achris]

Re: Which Engine Should I Use?

4 barrel 305 (230) should have a 1.50. I suppose if both motors were propped correctly it does not matter. Still quite a surprising difference with the swap nonetheless!

It was a 2bbl 305 in it's early life. The intake got a hole in it and since it's was easier to find a 4bbl intake than a 2bbl, a 4 bbl went on, along with a Quadrajet 4bbl carb, and new centre rise manifolds and elbows. We just left the 1.65 drive on a fit the next pitch up prop. Checked all the specs and everything is the same between the 2bbl engine and the 4bbl engine, including cam, heads, pistons, the lot..

Wont disagree that there are better options than a 305, but also not fully convinced a 4.3 can fill it's shoes in 100% of the applications out there.

Agreed.... I suspect a really big, heavy boat that needs the torque of a pair of 8s would struggle with a couple of V6s....

Chris......

 

[Bondo]

Re: Which Engine Should I Use?

4 barrel 305 (230) should have a 1.50. I suppose if both motors were propped correctly it does not matter. Still quite a surprising difference with the swap nonetheless!

Wont disagree that there are better options than a 305, but also not fully convinced a 4.3 can fill it's shoes in 100% of the applications out there.

Ayuh,.... I have a 4.3l,.... If goin' to a V8, the 350 is really the next logical step,....

The 4.3l V6 puts out nearly the same horsepower as the 305, 5.0l, V8,....
The V6 is nearly 100 lbs Lighter, so the 4.3l is absolutely Better than the 305, hands down, in My book,...