3.0L to LS engine?

[matt167]

I'm talking purely hypothetically.. What all parts are needed to swap to an LS type engine from a 3.0L. I would be thinking a garden variety 4.8L truck engine as they are $250-400

I know manifolds and the outdrive, but I know I'm missing more.. I have a Gen 2 transom assembly with a locked up 4.3 in my junker boat. It's missing the trim pumps and the 4.3L manifolds but complete otherwise

 

[Scott06]

You are missing more ... complete marine rated fuel delivery and ignition system.

Non hypothetically what are you trying to do? Swap a 3.0 for something more powerful?

 

[Rick Stephens]

Switching to a 4.3L from a 3.0 is not very hard. Build new front motor mounts and acquire the needed Merc parts.

 

[matt167]

You are missing more ... complete marine rated fuel delivery and ignition system.

Non hypothetically what are you trying to do? Swap a 3.0 for something more powerful?

IGN-1A coils for the LS are Mercury marine rated coils. That and the plug wires is the extent of the ignition system. Most of the rest of the stuff crosses over to marine ratings. Needs marine rated fuel pump, spark arrestor, starter and a few other things.. Holley Terminator X ECU is marine rated.

3.0L is a pretty heavy old thing. A 300hp smooth running aluminum ( fresh water only ) V8 would be quite nice... Just seeing if this might be possible... This is in a Starcraft Offshore 18' Tinny so anything heavier than the 3.0 might throw off the balance. Hence the aluminum v8 which weighs about the same while offering a lot more hp

 

[matt167]

Switching to a 4.3L from a 3.0 is not very hard. Build new front motor mounts and acquire the needed Merc parts.

4.3L may be too heavy for my boat though

 

[Scott06]

IGN-1A coils for the LS are Mercury marine rated coils. That and the plug wires is the extent of the ignition system. Most of the rest of the stuff crosses over to marine ratings. Needs marine rated fuel pump, spark arrestor, starter and a few other things.. Holley Terminator X ECU is marine rated.

3.0L is a pretty heavy old thing. A 300hp smooth running aluminum ( fresh water only ) V8 would be quite nice... Just seeing if this might be possible... This is in a Starcraft Offshore 18' Tinny so anything heavier than the 3.0 might throw off the balance. Hence the aluminum v8 which weighs about the same while offering a lot more hp

It more than just the coils , you need a different spark advance in a marine application vs truck or auto.

your best bet is a 4.3 that you have just need a new longblock and exhaust from your comments.

Bondojasoutside several members have done 4 cyl to 4.3 conversions on older tin starcrafts , I missing one can’t recall name of guy who redid it. They all swapped in newer v6engines. So don’t sweat the weight

 

[Rick Stephens]

4.3L may be too heavy for my boat though

3.0L bobtail engine 638 lbs. - alpha 1 package
4.3L bobtail engine 848 lbs - alpha 1 package


Adds 200 lbs. I did the same math before doing my upgrade. I also went to the boat manufacturer's options list and determined there was upgrade for my 17 ft hull available with an 4.3L instead of the base model 3.0L motor. The added weight on my 2200 pound boat did change the way it comes up on plane. I have added trim tabs to compensate for the tendency to run a bit nose high. But in general, adding 200 lbs and doubling the horses was all positive. Best part is, not only faster but a LOT quieter.

I'd bet that you will find your model Starcraft had an option to power with a 4.3. Be lots cheaper than inventing your own.

Rick

 

[Scott06]

Best part is, not only faster but a LOT quieter.
Rick

that really amazed me as well. Even running on the hose on the wagon, my 5.0 is quieter than my old 3.0! so much nicer for a sunset cruise

 

[matt167]

It more than just the coils , you need a different spark advance in a marine application vs truck or auto.

your best bet is a 4.3 that you have just need a new longblock and exhaust from your comments.

Bondojasoutside several members have done 4 cyl to 4.3 conversions on older tin starcrafts , I missing one can’t recall name of guy who redid it. They all swapped in newer v6engines. So don’t sweat the weight

the spark advance is all done in the tuning. Holley Terminator X will control it all and is marine rated.. I know that there have been 4.3L swaps on the cabin boats, and they also came that way later in the production runs. but I've also read here that the 4.3L will be too heavy for my open bow 18'. Same hull as Islander 18 though so possibly not.

 

[matt167]

3.0L bobtail engine 638 lbs. - alpha 1 package
4.3L bobtail engine 848 lbs - alpha 1 package


Adds 200 lbs. I did the same math before doing my upgrade. I also went to the boat manufacturer's options list and determined there was upgrade for my 17 ft hull available with an 4.3L instead of the base model 3.0L motor. The added weight on my 2200 pound boat did change the way it comes up on plane. I have added trim tabs to compensate for the tendency to run a bit nose high. But in general, adding 200 lbs and doubling the horses was all positive. Best part is, not only faster but a LOT quieter.

I'd bet that you will find your model Starcraft had an option to power with a 4.3. Be lots cheaper than inventing your own.

Rick

My boat is too old to have been optioned with a 4.3L and I know it never came with the straight 6.. It's a '71. I have a junker parts boat with the 4.3 Alpha Gen 2 stuff which is a 2000

 

[Rick Stephens]

My boat is too old to have been optioned with a 4.3L and I know it never came with the straight 6.. It's a '71. I have a junker parts boat with the 4.3 Alpha Gen 2 stuff which is a 2000

Easy test, have a 200 pound buddy sit on the doghouse and go for a spin. Or drop in a few bags of sand. That is if the boat is in ready to float condition.