Trimming....the drive that is!

[Irie308]

Hey all - it seems as if the more I read up on the forum the more I learn (this place is a wealth of info). For example I was not trimming the outdrive while cruising but as I've read trimming will improve gas mileage and give you a smoother ride etc. I tried it this past weekend and I've found there is a sweet spot right before the boat starts to somewhat skip off of every small wave. Can anyone share their knowledge/experience with trimming their outdrives in calm vs rough waters (as i do not have trim tabs). Also is there any benefit in installing hydrofoils on the outdrive?

 

[Gofirstclass]

Good question. Start with the basics....if your trim is set too low you're causing the bow to run too deep in the water which causes a lot of spray out to the sides, uses more fuel and slows you down. With the trim set too high what it's trying to do is lift the bow out of the water. This causes the 'porpoising' that you've experienced, which results in a rough ride even on calm water.

A good way to define the boat's sweet spot (and it changes depending on rpm's, fuel load, where passengers are seated, etc.) is to have the drive fully down when you're ready to go. Once you boat has started to transition from being in the water (at idle or at hull speed) to being up on plane, start trimming up. As the boat comes up on plane and you're pulling back on the throttle, keep trimming up until you hear the rumble noise that's caused when the prop is cavitating. At that point trim it back down a bit and listen to it. You'll hear the rumbling stop and the boat will pick up speed.

As passengers move around (from the stern to the bow in a bow rider) you may have to change your trim a bit, but do it in small steps and listen to the boat as you do it.

As far as trimming in heavy seas, I found it helpful to lift the trim up a bit to raise the bow. Not so much that it starts to porpoise, but just to lift it a bit. That helps to flatten out the waves.

I think hydrofoils help to keep a boat on plane at a lower speed and also reduce the likelihood that it will porpoise. But that part of it can be corrected with your trim. The actual benefit of hydrofoils may be more in your mind that any actual benefit. Some guys swear by them, some think they're a waste of money.

 

[Dave S]

I tell everyone that once you get to know your boat you should be able to trim your drive by "feel". Different boats require different levels of trim but you can always "feel" when you have the right amount of trim dialed in since the boat smooths out and speeds up. The only other thing about trimming the drive I will mention is that it is generally done when you are on plane. Also if the water is rough you may get a smoother ride if the bow can cut thru the waves rather than trying to ride over them. I know that was the case with my 240SD. I boated on an inland lake and on the weekends the waves would come at you constantly. Trimmimg the drive down planted the bow in the water and my boat would slice thru the waves rather than pounding over them if it was trimmed for the speed.

 

[SloBurn]

Every boat is different, so you'll need to learn how YOUR boat behaves to trim adjustments. I know of boats where a hydrofoil made a world of difference, and yet on other boats only slowed them down. I think the rule of thumb for hydrofoils is "if your boat digs in hard and takes a long time to plane, a foil can help" otherwise it's a waste of $.