How far up can you run the trim on an I/O under power???

[grouser]

New to I/O's and remember the PO telling me something about not to run under power with the outdrive up to high,,, but what's "to high"
thanks

[Tlowry]

Mine isn't an I/O but I watch the GPS and tweek it up until the speed peaks. I gain 4mph at a frog hair under 1/4 trim.

Although I doubt you'll see that kind of gain an a PB, but you may see and slight increase in RPM which would translate to better mileage.

[Bryden24shp]

You should have a trim/tilt gauge on the dash, watch that gauge when trimming. If it goes into the tilt side, drop it down. The reason not to, beside loosing performance is you'll tear your u joints out of the lower units horizontal shaft, that slides basically into the back of the engine. Sometimes when running with it too high, the joints can touch the boots, cutting them, and then water can get into the joint, through the seal and into the bilge of the boat.
You'll hear the motor gain RPM's and loose prop bite when you get too far up.
Play with it. You'll see where it runs best.
Have fun with it!

[grouser]

I do see the gauge,,, is there a point that I should not go over, (1/2?) while looking for the "sweet spot"?
Thanks for the help guys !!!

[Tlowry]

I doubt you would benefit from anything over 1/4. PO was probably warning you about running the drive near full up like you may be tempted to do in shallows.

[grouser]

That is what he was talking about now that I look back,,, in the shallows,,,,, and I appreciate the explanation thanks

[lemans81]

Yeah Trim only changes the motors angle by a tiny amount, I have run our pontoon at 3/4 trimmed up before for top speed although just a hair over 1/2 seems best. But when in trim the engine is still very much down. Now if we beach our stuff then you get into tilt, and tilt is where you don't want to run hard throttle. What I do on our i/o run abouts is tilt the motor up until the exhaust is out of the water, then back it back in a few inchs and then put it in gear and let fast idle in. Then I killed it about 12-14 feet from shore.

[babock]

Out of curiosity, what drive do you have?

[smltooner]

Changing the trim will not only increase your speed, it will also give you a smoother ride.

[grouser]

Yeah Trim only changes the motors angle by a tiny amount, I have run our pontoon at 3/4 trimmed up before for top speed although just a hair over 1/2 seems best. But when in trim the engine is still very much down. Now if we beach our stuff then you get into tilt, and tilt is where you don't want to run hard throttle. What I do on our i/o run abouts is tilt the motor up until the exhaust is out of the water, then back it back in a few inchs and then put it in gear and let fast idle in. Then I killed it about 12-14 feet from shore.

that some good info ,,,thanks for sharing it with me,

[grouser]

Out of curiosity, what drive do you have?

Mecruiser Alpha I

[grouser]

Changing the trim will not only increase your speed, it will also give you a smoother ride.

prevent porpoising right?? and ruff water by diving the nose a bit?