a little confused about trimming

[greenwell001]

hey guys


ive had my boat for 1 season and getting ready to get it out of storage, it is a 21 foot runabout.....onlu had ot out 5 times last season and was wondering about trimming up after you get on plane....how far do it trim it up and should that raise the rpm a little, i dont trim it up more than 1/4 of the guage soley because the guy that sold it to me (dealer) said thats where he runs his at.....i think maybe i could gain more speed and a better ride talking to couple buddies at work that have boats and they suggest to trim it up until i cant see the wake over my shoulder....how do you guys decide how much you trim up

 

[bruceb58]

Re: a little confused about trimming

I trim based on my fuel economy. I have a fuel flow meter.

 

[okboating]

Re: a little confused about trimming

In my experience, I trim until it porpoises and then back down. On my current deck boat, it really does not ever porpoise so I go by the rpm, it has a point were the rpms will sky rocket so I back down a fair amount from that. Trim is something that really takes some play, each boat is different and vary greatly. If you pull skiers or tubes, the best cruising trim will not give the hole shot that they need, so it is one of those things that you really have to figure out depending on the circumstances. One good thing about reaching a nice trim position is it allows you to scim over the waves instead of them smacking the front of the boat.
Trial an error my friend!
Dave

 

[woosterken]

Re: a little confused about trimming

green,
have a look at this article....................

http://www.clubmarine.com.au/internet/clubmarine.nsf/docs/MG19-2+Technical

woosterken

 

[Boatist]

Re: a little confused about trimming

On a day without a ripple on the water. I bring it up on plane then set the speed I want to run.
Next without moving the throttle I slowly adjust the trim while watching my GPS speed and adjust for best speed. If the boat porpoises at that point then trim back down until just stops. This will be your best fuel mileage for that speed and likely you highest RPM at that throttle setting.

This will be where the thrust from the motor is pushing the boat foward and not using power to raise or lower the stern.

A day with chop on the water or lot of boats and wakes then I trim for best safe ride.
This means I trim the boat where the bow comes down a little lower and has some contact with the water. How much contact depends on the size and type of chop and swells.
I want the deep V of the bow to help cut thru the wave instead of the a flater part of the hull farther back to just bounch over the wave.

Also running into the waves or swell you will trim the bow a little lower than when running with the waves or swell. You looking for the best ride for your boat and Crew.

 

[JoLin]

Re: a little confused about trimming

On a day without a ripple on the water. I bring it up on plane then set the speed I want to run.
Next without moving the throttle I slowly adjust the trim while watching my GPS speed and adjust for best speed. If the boat porpoises at that point then trim back down until just stops. This will be your best fuel mileage for that speed and likely you highest RPM at that throttle setting.

This will be where the thrust from the motor is pushing the boat foward and not using power to raise or lower the stern.

A day with chop on the water or lot of boats and wakes then I trim for best safe ride.
This means I trim the boat where the bow comes down a little lower and has some contact with the water. How much contact depends on the size and type of chop and swells.
I want the deep V of the bow to help cut thru the wave instead of the a flater part of the hull farther back to just bounch over the wave.

Also running into the waves or swell you will trim the bow a little lower than when running with the waves or swell. You looking for the best ride for your boat and Crew.

Me too.

 

[kyle f]

Re: a little confused about trimming

AH adjustring trim... Well when I had an I/O, I can tell you it was not a precise science and was situation dependant.

On calm water, I did it by feel and sound. Basically, accelerated about 3/4 throttle with trim in, and as I planed out would roll the throttle back a bit and start trimming out. I did it until I got a nice constat spray breaking off the front of the hull.. you can hear it.

Now, making a shar turn or pulling a tuber around in a lot of turns and back over chop... kept it almost completely in. ROugh water, about 1/4 out... see a big wake coming I will have to bust throug... trim in back in.. etc.

My Sea Ray was about 1/2 way on the gage would cause cavitation, this was apparent by the sound of the water coming out of the back of the boat, RPMS taking off, and speed slowing down. So, normal driving at about 25mph was with the trim just shy of this and about 1/4 ro 1/2 throttle... and otherwise it was adjust per situation almost like selecting which gear to use in a manual shifted car.

Best I can tell you on this, is give it as much trimout as possible that doesn't cavitate the prop, doesn't cause an uncomfortable ride in the boat, or cause horring handling. You may always need to trim in for a tight manuver, but you will get your best economy trimming out as much as possible.

 

[bruceb58]

Re: a little confused about trimming

but you will get your best economy trimming out as much as possible.

This should not be a blanket statement. Will depend on the boat and engine. Have you measured with a fuel flow meter?

My boat gets worse fuel economy past a certain trim. I measure mine with a fuel flow meter that is hooked up to a GPS which calculates MPG.

 

[greenwell001]

Re: a little confused about trimming

wow
thanks for all the usefull info

sounds like i could benfit from a fuel flow meter....does it have to be hooked up to a gps like bruce's setup

 

[bruceb58]

Re: a little confused about trimming

It doesn't have to but harder to calculate. For example, your fuel flow dropped but so did your speed. Would just have to do a calculation on the fly to be able to tell what was the most fuel efficient.

 

[greenwell001]

Re: a little confused about trimming

makes a lot of sense bruce....i have looked a little on iboats for just a flow meter and was wondering if i could just use the tom tom gps on my truck on my boat to see exact speed....i really can afford to spend 600 dollars on a combo unit that reads fuel flow...any suggestions?

 

[bruceb58]

Re: a little confused about trimming

could just use the tom tom gps on my truck on my boat to see exact speed.

Sure..you can use any GPS if all you want to know is speed.

 

[Silvertip]

Re: a little confused about trimming

You don't need a trim gauge, gps or fuel flow meter to tell you what optimum trim is. First, optimum trim varies greatly by speed and water conditions so it is never the same. Next, the load you carry and it's distribution in the boat affects trim settings. The best gauge for setting trim is the seat of your pants and your ears. Once on plane and at the speed you want to run at begin trimming out. When the rush of the water begins to subside and the boat settles into a nice smooth ride you have it. You can feel it. But you will never get this right unless you experiment. You won't hurt anything by trimming in and out. But you will at least learn what too much and too little is. Happiness is somewhere in between.

 

[109jb]

Re: a little confused about trimming

You don't need a trim gauge, gps or fuel flow meter to tell you what optimum trim is. First, optimum trim varies greatly by speed and water conditions so it is never the same. Next, the load you carry and it's distribution in the boat affects trim settings. The best gauge for setting trim is the seat of your pants and your ears. Once on plane and at the speed you want to run at begin trimming out. When the rush of the water begins to subside and the boat settles into a nice smooth ride you have it. You can feel it. But you will never get this right unless you experiment. You won't hurt anything by trimming in and out. But you will at least learn what too much and too little is. Happiness is somewhere in between.

I agree 100% with what Silvertip said. There are so many things that affect trim that setting it by a gauge will set it at non-optimum every time. As far as I'm concerned the trim gauge is only for getting you in the ball park. I never really think much about how I trim, I just do it. If I had to describe it in words I would say I get on plane at speed and trim out like Silvertip said. As you trim, the bow will rise, speed and rpm will increase a little and the ride will smooth out. If the bow starts bobbing it is trimmed out too much. I have an outboard powered boat and my trim gauge doesn't work and probably never will because I don't need it because I can look at the motor to see where it is at. With an I/O the gauge is nice for getting you close since you can't see the outdrive but I would only consider it a reference and would go by the seat of the pants for the final setting.

 

[JimS123]

Re: a little confused about trimming

My I/O doesn't have power steering. When I'm perfectly trimmed the torque on the wheel is just about zero.

 

[H20Rat]

Re: a little confused about trimming

'perfect' trim doesn't exist.

Perfect trim suitable for a single variable does. So if you want to trim for absolute best fuel economy, you need a gps/fuel flow combo. If you want the best ride, zero torque steer, or wake size, that is seat of the pants. Trimming for speed is obviously GPS. (don't go by feel/ear on this one, an engine too high will ventilate a little and the rpms will go up, making it SOUND like you are moving faster than you are. Dropping trim a hair might give you an extra mph. only a gps will tell you that.)

ohh, and all those trim setting vary with load/temperature/water/wind conditions.

 

[GXL205 Deke]

Re: a little confused about trimming

You don't need a trim gauge, gps or fuel flow meter to tell you what optimum trim is. First, optimum trim varies greatly by speed and water conditions so it is never the same. Next, the load you carry and it's distribution in the boat affects trim settings. The best gauge for setting trim is the seat of your pants and your ears. Once on plane and at the speed you want to run at begin trimming out. When the rush of the water begins to subside and the boat settles into a nice smooth ride you have it. You can feel it. But you will never get this right unless you experiment. You won't hurt anything by trimming in and out. But you will at least learn what too much and too little is. Happiness is somewhere in between.

Thanks all for taking all the time you do to explain these things, I have only had mine.. [as in I finally own one] 1 day trip and Labor day weekend last summer, and this whole trim business has been a mystery. This thread is great stuff. I started to play with trim a lot last labor day because we traveled quite a ways from where we put in vs where we were hanging out at the largest lake in Oklahoma, and I understand what you mean by feeling it, with the bow raising a little and the ride getting very smooth and just gliding across the water. Great stuff! I just needed to read you all talking about this.

Great Post Greenwell!

 

[greenwell001]

Re: a little confused about trimming

you guys are the most helpful people in the boating industry.....i actually feel like i have enough knowledge through you guys to not be nervous about owning a boat....i am one of those types of people that have to know every thing about something to be comfortable with it....this is an awesome information highway

thanks iboats

 

[golf101]

Re: a little confused about trimming

I'm on my second boat, and the trim level varies dramatically between the two. I barely trimmed at all (maybe 1/8 on the trim gauge) on my old boat for optimum performance, and go closer to 1/4 on my new boat. Agree that trim is a matter of experimentation and water conditions. Not sure what your friends mean about not seeing the wake over your shoulder, but I have noticed that the trim on my new boat is about right in low wave conditions when I look over the side and see the wake breaking about mid-boat (or about where I am sitting at the steering wheel or slightly behind).

 

[greenwell001]

Re: a little confused about trimming

golf101 (nice screen name, my first love is golf)

i think they meant to trim until the wake is behind you and you are just running on the flatter part of the boat, kinda like it is skipping accross the water .......that seem like less drag, more speed, better ride, and easier on the drive and steering from what i have learned on this thread....am i right guys?