Trim Basics

[harbormaster]

Steve Dold (RiverRat) was kind enough to allow me to drive his baby (2000 model 18 classic) last Saturday. I was a stranger to the trim button. Previously I had driven early 70's 18's with Ford/Volvo drivetrain and no trim.

What a difference.

The older model in my opinion was slightly docile compared to the magnum powered 18 with trim.

With the large number of folks frequenting this website that are buying 18s (present company included), I thought it would be a good idea for some of you who are Really experienced to give a tutorial on the tips/tricks of trimming an 18.

Folks who are experienced with newer 18's should speak up first. Are there handling characterics unique to different years? (OMC, Volvo, Mercruiser?)

Please put some thought into it before responding. I think that this will be the start of a new Boat handling forum unique to each Donzi model. What do you guys think?

[RedDog]

18 Classic OMC King Cobra -

Generally I have found that the faster I go, the more I can trim up - the more I trim up the faster I go - up until a point - I can trim too high and bust the prop loose.

If trimmed too high for the speed, porpoising results so either give it more throttle for more speed, trim down, or sometimes dropping the tabs helps stop the up-and-downs.

[Ranman]

My 18 Classic MAG350 / Bravo combination is VERY sensitive to trim. I can pick up several hundred rpm and 5+ mph top end by trimming her out. With the drive all the way down, the boat will handle the rough much better. For speed, as I trim up, I can feel the entire boat loosen up and start to "dance" on top of the water. This can get dicey in the rough and lead to lots of air time (both wanted and unwanted).

The way I look for optimum trim at WOT is as follows: As I trim up I can feel the boat loosen up, pick up speed and the rpm will also go up. This usually equates to the needle being half way up the trim guage. As you keep trimming up, eventually the motor will start picking up rpm, but your speed will decrease. You'll notice the prop slipping and the rpm creeping up too high. At this point you've gone too far. The key for me at least is to get the trim as high as possible while still maintaining a good bite with the prop. If I get it too high I just bump the prop back down a bit and we're all set.