[juttmk]

Recently purchased a Z220 7.4 with a chewed up 21 pitch aluminum prop. After installing a new Mercury Mirage Plus 14.5" x 19 pitch prop I was shocked to only be getting around 42mph out of this setup. How far are most of you guys trimming up on smooth water?

I just repalced the U joint and gimball bearing, which I read that over trimming can put additonal stress on these componets.

WOT: 4700

[ShabahZ280]

There's really no right or wrong trim, it's all based on the conditions of the water, and how comfortable you are with the porpoising from trimming too high.

I usually start off with trim fully down, once it planes, adjust between 1/4 and 1/2 on the gauge. That's pretty much the sweet area.

4700 WOT sounds about normal. The numbers we usually see for WOT on a big block is between 4200 and 4800. Just not sure if the 19 pitch is correct for your prop. Stop by the "Prop Talk" section and talk to some of the prop guru's about what may be best for your setup.

[juttmk]

Thanks for the reply!

[Firestone]

My 14.25 x 17P just took me up to 49 at Powell. I have a smaller boat and smaller engine. Listen to ShabahZ280, he is Da Man

Firestone - 2000 Mariah Z202 5.7L MAG Alpha I Gen II

[scaverly]

I'm running a 17 pitch stainless steel on a 1991 Mariah 2200ZC , getting 50mph trimmed up , I would say less than half, hope this helps. Shawn

[kylakerat]

42 Mph on the speedometer? If so, I wouldn't be too concerned as your WOT is about right. The water pressure speedometers are notoriously inaccurate. A speedo app on your phone using GPS would be more accurate. Mine varies 5-8 MPH from GPS readings.

As far as trim...run it up until it's starts porpoising then back down just a touch. The more of the hull you can get up out of the water, the faster it will run. I don't pay any attention to my trim gauge. I look at the wake behind the boat, and just keep it from porpoising.