Potential Engine Change

[Fleetwin]

Boat: 2009 Larson 18' SEI (This boat WAS offered with the 4.3L)
Engine: 3.0L GLP-J (red)
Drive: SX
Opportunity: 4.3L "drop in".

I have the boat listed above. I love the boat but the 3.0 is adequate. Plus, I don't like the vibrations and noise from the 3.0. I have been in a sister boat with the 4.3L. What a difference. This is the last boat I'll ever own and like it enough to modify it.

I have the opportunity to pick up a great deal on a 4.3L V-P MPI drop in. I realize that I need a y-pipe and tubes, coupler, etc. but that is covered. Otherwise, the swap looks very straightforward.

The gear ratios are different. I believe the 3.0L is 2:1 and the 4.3 calls for 1.8:1.

Questions:

Can I overcome this ratio difference with Prop's? Currently running a 17" pitch (3.0L) and WOT RPM's are right at 4600 (light load)?

Thoughts?

Thanks.

 

[alldodge]

Boat: 2009 Larson 18' SEI (This boat WAS offered with the 4.3L)
Engine: 3.0L GLP-J (red)
Drive: SX
Opportunity: 4.3L "drop in".

I have the boat listed above. I love the boat but the 3.0 is adequate. Plus, I don't like the vibrations and noise from the 3.0. I have been in a sister boat with the 4.3L. What a difference. This is the last boat I'll ever own and like it enough to modify it.

I have the opportunity to pick up a great deal on a 4.3L V-P MPI drop in. I realize that I need a y-pipe and tubes, coupler, etc. but that is covered. Otherwise, the swap looks very straightforward.

The gear ratios are different. I believe the 3.0L is 2:1 and the 4.3 calls for 1.8:1.

Questions:

Can I overcome this ratio difference with Prop's? Currently running a 17" pitch (3.0L) and WOT RPM's are right at 4600 (light load)?

Thoughts?

Thanks.

Yes, you should be able to. Your gaining about 80HP which might have to a 21 to 24 pitch prop. Just a guess. Have a similar issue I have been pondering with increasing HP not engine size

 

[smassey22180]

I agree on the 21 or 23p prop but not sure you can get away with 2:1. I had a 17p on my 190 hp 4.3 and was hitting 5300 rpm. Now with a 19p I still kit 5k. Today the UPS man is bringing me a 210 hp GS 4.3 4 barrel and intake. I will try my 19p prob but expect to go to a 21p. How did you find a MPI? That was my preferred swap. I went from a 3.0 in my previous boat to a 4.3 in my new one and that 3.0 shaking drove me crazy.

 

[Fleetwin]

Smassey, The MPI's are out there. I saw some at Michigan Motors.

 

[smassey22180]

Interesting that the Volvo MPI is less cost than the Mercruiser.

 

[Bondo]

Boat: 2009 Larson 18' SEI (This boat WAS offered with the 4.3L)
Engine: 3.0L GLP-J (red)
Drive: SX
Opportunity: 4.3L "drop in".

I have the boat listed above. I love the boat but the 3.0 is adequate. Plus, I don't like the vibrations and noise from the 3.0. I have been in a sister boat with the 4.3L. What a difference. This is the last boat I'll ever own and like it enough to modify it.

I have the opportunity to pick up a great deal on a 4.3L V-P MPI drop in. I realize that I need a y-pipe and tubes, coupler, etc. but that is covered. Otherwise, the swap looks very straightforward.

The gear ratios are different. I believe the 3.0L is 2:1 and the 4.3 calls for 1.8:1.

Questions:

Can I overcome this ratio difference with Prop's? Currently running a 17" pitch (3.0L) and WOT RPM's are right at 4600 (light load)?

Thoughts?

Thanks.

Ayuh,..... Maybe,..... Maybe not,.....

I've got a 4.3LX Merc, with a 1.65:1 drive, a 20" ssteel prop holds it to 4800 rpms, at 'bout 43mph,....

I slapped on a 1.98:1 drive, 'n even a 26" prop wouldn't control the rpms, 'n the speed loss,...

'n props bigger than 23" are pretty tough to find,...

 

[Fleetwin]

Good to know, Thanks Bondo.

I really do not have an issue with having a basically new drive rebuilt, with different gears, but I'm cheap and exploring options.

The way I drive the boat, WOT would not be an issue. I'll bet a great holeshot! But, right is right. Might as well do it that way.