The big powered LS platforms use blocks like the LS Next block that are not skirted. The skirted block is just a windage issue that needs to be solved. To me it's all about the efficiency of the combustion chamber.

How is the valve train geometry of the LS compared to the BBC?

Are the ports laid out better or is that part taken care of with the aftermarket BBC heads?

I think its been mentioned before but the bigger and heavier the boat the more torque your going to need. For me personally id guess that a 28-31' boat is about the limit for twin small blocks...after that unless you have a light layup 35 race boat i don't think there will be an advantage for a small-block motor. The ONLY thing i can see is lets say you had two boats, lets say they are both brand new 38' offshore race boats...both with lets say twin 800hp engines....ones got LS motors the other is BBC motors.....both are up on plane going 35-40mph and both gun it at the exact same time......i think the LS boat "might" accelerate faster to top end compared to the BBC motor and possibly use a little less fuel.....but is the tradeoff on the lower end and possible savings in fuel economy worth it i guess would be the question. Most boaters dont realy care about fuel economy....if they did they wouldn't be in a go-fast to start with!
To me the small-blocks have a place in the smaller boats but not too much on the larger ones, but i could be way off in my thinking

I wouldn`t throw this out of bed

https://shop.prestigemoto.com/i-3049...d-turnkey.html


Wally you hit the nail on the head !

This would hold if the SB and BB had the same operating rpm.
It would hold even if both had the same power and the same gear ratio, and of course the SB has higher revs.

If both have the same final power and both have the same propeller shaft rpm, at least physically the SB should win because of the lower mass and better design that gives it more even torque throughout the rpm range. This is exactly what can be seen in the comparison between Mercruiser's 8.2 HO and Volvo Penta's 430 hp engine.

The most important thing is the power available at a given moment, not the torque. Torque you get with the correct use of power, and in this case it is thequestion of revolutions of the propeller, and the propeller. Centuries ago Archimedes already said that with a long enough lever he could lift the earth...


Extreme example:

Air and water are both liquids, except that water is a liquid, but the basic laws of propeller propulsion apply to both very similarly.

I am a modeler and in two my models have an identical brushless innruner with 2 Kw at 60,000 rpm.
In the small 2.8 lbs pylon the model is directly driven by a 4.1x6 propeller and the model reaches around 280 mph but has poor acceleration, it is werry tricky for hand start.
In a 6.2 lbs hotliner this motor has nothing to do with direct drive, for so I added a 5.2 planetary reducer and now motor turn 16x16 propeller and the model is a total dragster going 130 mph vertical. It pull from hand with around of 20 lbs.
Same engine both times, but different propeller speeds.

Looking into the RS-X BBC heads, and they really feel like an LS inspired BBC head. Has a separate valley cover with coolant. Appears to raise the runners.

1000hp NA from 632 CID.

There is a lot more potential on those heads.

They seem relatively inexpensive for what they are.

I got on the wait lis for the bare unported heads a few weeks ago. I can’t wait.


Engine labs article

Great stuff and love new tech but the weak link in the I/O setup is the transom assembly. Not sexy but thats where the advances need to be made. The engines alone are reliable.

Subscribed!!!

Looking forward to hearing about the process and results.

What are you thinking for the 70cc chamber? Large D-dish pistons?

What is your HP goal?

Since we would be doing turbo I’d go with a symmetrical dish with a CR in the 8.25:1 area.

HP goal? All of it! 😁😂