using trim?

[rtgnyg]

I have an 18 foot with a fl115la with electric trim. In my area i have lots of shallow water to contend with and am wondering how high I can trim the motor. My rule of thumb i've been using is to trim the motor up and try to watch the water stream from the engine. When doing this the engine sounds WAY different. Sounds like its really working hard and really kinda roars when you move the throttle. My question is is it ok to run like this? For how long? Ive hit bottom when trimmed down a few timesin shallow areas, not hard but very unnerving when it happens.

 

[Chris1956]

The motor must have the ability to pull enough cooling water, so that is the limit of your trim. If it is shallower than that, it is time to push the boat. Remember the motor is not under a normal load when trimmed high, so be careful with the throttle.

 

[southkogs]

And just so it's said (you may be all set with this): trim and tilt are not the same thing. Trim is for adjusting the motor angle to the boat to effect how the hull is interacting with the water. Tilt is for bringing the motor depth up shallow or for trailering. Generally, there is a trim range where you can apply full power and a tilt range where you really are only supposed to operate at low RPMs.

I'm used to having to keep low RPMs for shallow water use.

 

[JimS123]

Put the boat on the trailer and then trim up until you see that the prop and skeg are above the bottom of the boat. Note the position on your trim gauge so you can get back there when you're in the water. If you don't have a trim gauge, install one.

Once you're in the water and at that setting check for proper cooling water intake. If all is good you found your sweet spot.

 

[Watermann]

Sounds like you should think about a jack plate or a jet LU even.

 

[Silvertip]

The motor sounds different when trimmed high because the exhaust is very close to the surface of the water so the muffling action is lost. You really need to be careful so the engine does not lose its ability to take in cooling water.

 

[Texasmark]

The motor must have the ability to pull enough cooling water, so that is the limit of your trim. If it is shallower than that, it is time to push the boat. Remember the motor is not under a normal load when trimmed high, so be careful with the throttle.

Yes and no. If you have a low water intake on the LU like most current production engines, too high is when the prop is so high that the boat speed starts falling off and the revs start increasing disproportionally, assuming you are at WOT or thereabouts. However since you mentioned rocks one can assume you mean at slow speed where you are dodging the boulders and there Bro. Chris has it.

On the different sound, at slow speed, you can hear the exhaust exiting as Silvertip said, but at WOT you can hear the blades beating the water and the engine humming.