Re: 4.3 out drive
Prop pitch, not prop diameter.
The gear ratio in the drive, and the pitch of the prop work together to get your engine in the desired RPM range.
I'm going to try to compare this a bit to a car, so hang with me..
Say you have a car that can have both the 4.3 and a V8 installed. This car has a manual transmission, and is rear wheel drive.
This isn't a perfect comparison, because obviously you can change gears at will in a car. With a boat you can't.
Say for argument sake this car only has 1 forward gear. The cars transmission, and rear gears work together to properly get the correct ratio for the engine to run right in its power band (enough Umph to pull away from a stop, but not geared too low that the engine would over rev on the highway). The transmission would be the equivalent of the drive on the boat, and the rear gears are like the prop.
OK... So the car with the 4.3L engine needs the transmission ratio to be about the equivalent of say second gear to be within the correct power range (not over-revving, and not lugging down the motor).
The car with the V8 needs to have the transmission ratio about the equivalent of say third gear to be within the correct power range for the same reasons as the 4.3L.
Now let's say you blow the transmission in the V8 car, and find a replacement out of a 4.3L car. Remember the transmission gear ratio for the 4.3L is higher than the one used for the V8. That means that the V8 engine will have to spin faster to turn the rear gears (prop) at the same RPM it did before. In fact, it may have to spin faster than what the engine was designed for.
You may be able to compensate by changing out the rear gears to lower the RPMs, but it may never be ideal.
That's what you face with your boat. Placing the engine in front of a drive with a higher gear ratio than needed will require the engine to spin faster with the same prop. You may be able to compensate by putting a higher pitch prop on to drop the RPMs, but it may never be as perfect as using the correct drive.
still so tempting. I was just over simplifying the scenario was looking at it as crank still spins one turn at a time.
