3.0L to 4.3L Swap

[Fleetwin]

Hello All,

I have a 2009 Larson 18' Fish and Ski. I love the boat. It is very well built but a bit heavy. This will probably be the last boat I ever own.

It has a 3.0L GL-PJ with an SX Drive (32 hours). While adequate, the 3.0 is a bit cold blooded, noisy and generally just very old school. I've never been a fan of the old GM Industrial pushrod fours. I have some experience with 4.3's and they are an entirely different animal as far as noise, etc.

The same boat was availble with a 4.3L/same SX drive w/different ratio. I verified, with Larson, that the boat was the same regardless of engine choice.

I am seriously looking at upgrading to the 4.3L. Again, the boat is perfect for me and my needs. Money is really not the issue as I figure I can regain some expense by selling my perfectly good 3.0L Bobtail. Plus, I bought the boat far below value. I have a freind that can get me a good deal on past model V-P 4.3's. Either 190 HP (carbed) or 220 HP (EFI). Both of those would be Bobtails. I do realize that I will need a Y-pipe with connecting hardware, etc.

With all that, I have some questions:

1. I realize the drive ratios are different. Can I overcome that with Prop? I currently run a 19". It is the perfect pitch for the current 3.0 set up (decent hole shot and 4600 RPM WOT) with 40 MPH indicated GPS.

2. Are the engine mounts in the same place? My engine compartment is HUGE so there would be no issue with clearances or redoing a few things.

3. Are the two engines; 3.0 vs. 4.3 basically "plug and play" electrically? I can get a hold of the 4.3 installation manuals.

4. Other issues I may encounter?

Thanks.

 

[Bondo]

Re: 3.0L to 4.3L Swap

Hello All,

I have a 2009 Larson 18' Fish and Ski. I love the boat. It is very well built but a bit heavy. This will probably be the last boat I ever own.

It has a 3.0L GL-PJ with an SX Drive (32 hours). While adequate, the 3.0 is a bit cold blooded, noisy and generally just very old school. I've never been a fan of the old GM Industrial pushrod fours. I have some experience with 4.3's and they are an entirely different animal as far as noise, etc.

The same boat was availble with a 4.3L/same SX drive w/different ratio. I verified, with Larson, that the boat was the same regardless of engine choice.

I am seriously looking at upgrading to the 4.3L. Again, the boat is perfect for me and my needs. Money is really not the issue as I figure I can regain some expense by selling my perfectly good 3.0L Bobtail. Plus, I bought the boat far below value. I have a freind that can get me a good deal on past model V-P 4.3's. Either 190 HP (carbed) or 220 HP (EFI). Both of those would be Bobtails. I do realize that I will need a Y-pipe with connecting hardware, etc.

With all that, I have some questions:

1. I realize the drive ratios are different. Can I overcome that with Prop? I currently run a 19". It is the perfect pitch for the current 3.0 set up (decent hole shot and 4600 RPM WOT) with 40 MPH indicated GPS.

2. Are the engine mounts in the same place? My engine compartment is HUGE so there would be no issue with clearances or redoing a few things.

3. Are the two engines; 3.0 vs. 4.3 basically "plug and play" electrically? I can get a hold of the 4.3 installation manuals.

4. Other issues I may encounter?

Thanks.

Ayuh,.... #1,... I doubt a 23" or 25", if ya could find 1, would be big enough,...
So,... Ya, change the gear ratio,....

#2,... Nope, the 4.3l mounts are on the side of the motor, not the front,....
New motor mount blocks will need to be glassed in,...

#3,... I'm guessin' the cannon plug changes with Vintage, over motor styles, but donno for sure,..

 

[Fleetwin]

Re: 3.0L to 4.3L Swap

Thanks Bondo.

I figured the drive issue would be just that. However, I can get someone to go through the drive and change the gears, if need be. I understand it's not that hard on an SX. Just $$$ for parts and set up.

Electrically, that can be figured out. I think.

Fortuneately, Larson does a very nice job mounting their engines. They sit on a "Starboard" mount. Larson told me that their "Starboard" mounts are all they use. The mounting areas, underneath, all go into fiberglass stringers and supports. I think that is doable.

Anyway, thanks again.

I think it's a matter of getting the drive ratio right, wiring and placing new mounts. I am told the V-P "bobtails" come with mounts.

Since my drive is spotless, I may be able to arrange some sort of an exchange. Off to hunt for that possibility.

 

[Scott Danforth]

Re: 3.0L to 4.3L Swap

you may be able to sell your whole setup and use to fund a new drive

here is a place to look for parts that I know of. many out there New - Used Outboard Motor Parts - Marine Parts Outlet

 

[Fleetwin]

Re: 3.0L to 4.3L Swap

Thanks Scott!

 

[Bondo]

Re: 3.0L to 4.3L Swap

Thanks Bondo.

I figured the drive issue would be just that. However, I can get someone to go through the drive and change the gears, if need be. I understand it's not that hard on an SX. Just $$$ for parts and set up.

Electrically, that can be figured out. I think.

Fortuneately, Larson does a very nice job mounting their engines. They sit on a "Starboard" mount. Larson told me that their "Starboard" mounts are all they use. The mounting areas, underneath, all go into fiberglass stringers and supports. I think that is doable.

Anyway, thanks again.

I think it's a matter of getting the drive ratio right, wiring and placing new mounts. I am told the V-P "bobtails" come with mounts.

Since my drive is spotless, I may be able to arrange some sort of an exchange. Off to hunt for that possibility.

Ayuh,.... that's the definition of a Bobtail motor, Complete, 'n ready to drop in, no extra parts necessary,...

 

[Fleetwin]

Re: 3.0L to 4.3L Swap

Ayuh,.... that's the definition of a Bobtail motor, Complete, 'n ready to drop in, no extra parts necessary,...

Ayuh!:joyous:

I've seen actual pic's of the engines. NOT sales images. Everything is there for mounting.

I like the fact that I don't have to break the transom assembly seal. The boat is 100% dry.

Do you see isues with going EFI over carbed? As I understand, all of the EFI components are engine mounted. Just plug in a fuel line and convert the electricals. Agree?

Thanks.