Planetwarmer

Why would you need to aerate the props on take off? Is that to get the RPMs up quicker?

The reason Im asking all of this is, I took a 28 Skater out and the guy that actually borrowed the boat said the owner told him to trim up the motors on take off.

Too Stroked

Too much bite + motors that don't make much power low in the RPM range = need to "slip the clutch" a bit. Aerating the props accomplished this. On a 2.5, it also sounds downright wicked.

A number of years ago, some larger offshore race boats were experimenting with 2 speed transmissions to solve the same problem. It was later outlawed though. Again, it sounded pretty cool.

KEVLARKAT32

Shaun Torrente is in process of building me pair 300 x with 3.2 stroker crank , should be close to 370 hp , they will be installed on my 32 Kevlar Skater , hoping to see 105-110 mph


I know the 2.5 is great engine but for me rebuilding every 100 hrs is a pain . A pair of stroked 3 litres is going to push my boat as fast when it had 3-2.5

waterboy222

Yes and no. The motors need to be trimmed way up when idling so that theres not so much resistance against the prop and causing the motor to bog down. As you take off, you trim it FROM 7 or 8 (at idle) down to 0 or 1 (for planing/running). Trimming it up as you take off would just cause it to porpoise. Trimming it towards 0 as you throttle keeps the props spinning and the bow coming down, or at least thats how he taught me to run it..

RBT

On all Mercs, if the midsection is full of water the motor has a severe exhaust restriction. This is only the case at off plane speeds. The exhaust pressure needs to push the water out before the motor can make any real power.
Add that the 3.0 series motors are famously soft on bottom end power.
I used to run -12 lines to the cav plates on the 300 pro max motors and drill exhaust reliefs in the tuner to help them accelerate faster. (1/2 hole is all it needed)

waterboy222

Very interesting. Ive not seen that in any of the offshore motors. Was this on the drag motors or?

RBT

No not on the drags, they float much higher and have way way more power.
This was on my bigger boats.
To be frank, for the most part there has been zero motor development for the offshore guys, the Torrente 3.2 motors will be COOL. I hope the results will be posted. My only concern with the 3.0 and 3.2 motors is the stock rods are WEAK, the pistons are cast and are not real happy with rpm. Adding the .2 stroke increases the piston speed... meaning you need to keep the rpm lower to maintain the same actual piston speed.
It certainly works, there are just some things that everyone needs to be aware of.

northernoffshore

Happen to me before on a cat with twin . wouldn't idle right. Gene at g force stood on the nose of the boat and everything was great. G force was great with outboards.