Using the Trim Properly

[ninjah]

This is a super boat 101 question so please bear with me. I just got a Mark II with a 40hp Mercury with automatic trim. I tried to do some research online but couldn't find anything specific to ribs.

Problem, I don't really understand how the trim is intended to work, when to adjust it, and what adjustments to make in different scenarios. I realize I can control the bow, etc.. with it but when I bought the boat I was told the bow normally raises up until it starts planing. Then someone else told me I should use the trim to control that and remain confused. I don't want to do something stupid and flip my boat. Also, the trim allows the motor to come all the way up (obviously) but also down pretty far. Thanks for any help on this.

[Nos4r2]

Automatic trim? Not heard of that one! Post a pic of the motor and controls please.

[ninjah]

Sorry, didn't mean automatic trim! I mean the trim is electronic and operates via switch as opposed to manually moving it up and down. I have a switch on the motor and on the console shifter.

[henryfreston]

Basically you can use the trim to obtain optimum fuel economy and performance.

When moving from rest onto the plain it is best to have the engine trimmed all the way down (so the energy from the prop forces the boat at an angle up and out of the water)
As you get onto the plane, trim up until the outboard is at a 90 degrees (in flat conditions) to the transom. You will notice a change in speed and RPMs when trimming out. But trimming out you are allowing the bow to drop so the boat moves more efficiently through the water.

Henry

[captnjack]

I'd suggest taking a basic boating course like those hosted by the power squadron. United States Power Squadrons® Safe boating fun thru education

They can help you understand trim.

The proper use of the trim will depend on the sea state, the number of people and load aboard, and the distribution of that load. Its not something which can be learnt very well via the internets.

[Nos4r2]

Originally Posted by henryfreston

Basically you can use the trim to obtain optimum fuel economy and performance.

When moving from rest onto the plain it is best to have the engine trimmed all the way down (so the energy from the prop forces the boat at an angle up and out of the water)
As you get onto the plane, trim up until the outboard is at a 90 degrees (in flat conditions) to the transom. You will notice a change in speed and RPMs when trimming out. But trimming out you are allowing the bow to drop so the boat moves more efficiently through the water.

Henry

Henry, you need a lesson in using trim.

Set off with the motor trimmed at 90 degrees to the keel. Increase the trim angle (trim out) til you're skimming along nicely when you're planing. You'll feel the 'sweet spot'.
On an inflatable, be careful of trimming out too far, specially if it's windy as you can flip the boat. You'll know if it's too far as the boat will start to feel 'loose'.

If you're heading into the waves, trim in to keep the bow down to stop the boat coming over backwards.

A pretty good guide to being trimmed correctly is that if it's right, your comfort level will be noticeably better. You'll get the minimum of slamming and the tendency to 'double slam' and porpoise will be less-specially when you're trimmed out too far.


As Capnjack says, take the course-you'll learn it far better with experience and training than just trying it.

[henryfreston]

Originally Posted by Nos4r2

Henry, you need a lesson in using trim.

Set off with the motor trimmed at 90 degrees to the keel. Increase the trim angle (trim out) til you're skimming along nicely when you're planing. You'll feel the 'sweet spot'.
On an inflatable, be careful of trimming out too far, specially if it's windy as you can flip the boat. You'll know if it's too far as the boat will start to feel 'loose'.

If you're heading into the waves, trim in to keep the bow down to stop the boat coming over backwards.

A pretty good guide to being trimmed correctly is that if it's right, your comfort level will be noticeably better. You'll get the minimum of slamming and the tendency to 'double slam' and porpoise will be less-specially when you're trimmed out too far.


As Capnjack says, take the course-you'll learn it far better with experience and training than just trying it.

I did a pb2 in swansea bay and that was what I was taught

maybe I should go elsewhere to a more reputable place

Problem is they are so expensive and after paying for one....well I have always fancied a garmin 451s

[Nos4r2]

Originally Posted by henryfreston

I did a pb2 in swansea bay and that was what I was taught

Trimming out makes the bow rise, and some motors will trim right in , pushing the bow right down making the bow 'plough' if the trim limit pin is too far in.

Originally Posted by henryfreston

maybe I should go elsewhere to a more reputable place

Might be a recall problem?

Originally Posted by henryfreston

Problem is they are so expensive and after paying for one....well I have always fancied a garmin 451s

More experience is all you need Get the boat out

[henryfreston]

Originally Posted by Nos4r2

Trimming out makes the bow rise, and some motors will trim right in , pushing the bow right down making the bow 'plough' if the trim limit pin is too far in. Might be a recall problem?

More experience is all you need Get the boat out

Once exams are over

[ninjah]

Thanks everyone, very helpful.

[HUMBER P4VWL]

Originally Posted by Nos4r2

Trimming out makes the bow rise, and some motors will trim right in , pushing the bow right down making the bow 'plough' if the trim limit pin is too far in. Might be a recall problem?

More experience is all you need Get the boat out

Agreed, was panicking then Henry!

To be fair, once you have played around it becomes quite obvious. If you Trim out when moving from rest the bow goes too high. trim in on the plane and you feel the bow drop too much and create more drag as it ploughs through the water, rather than trimming out and skimming along with the least amount of boat in the water, too much though and the engine loses grip eventually.

Also on relation to to much the unit is normally geared. From fully out/up, when you lower it it will move quite quickly, then hits a point where it keeps going but much more slowly, from here to fully in is usually the min and max position of trim whilst underway. The fast bit is the "tilt" the slow bit is the "trim" when engines have "power tilt and trim".... Logically.

Hi res Anglesey pics

Alex Whittaker / Shedpix Donations for Round Anglesey Macmillan 2014 https://www.justgiving.com/Rib-net

[jyasaki]

Nos said pretty much everything I was going to.

One other note: I often adjust trim to get a smoother ride over chop or tight swell. If you notice the boat rocking and pounding, you can often adjust trim either in to keep the front from leaving the water, or out to get it to land more stern-first (which will lessen the shock on landing.) Mostly practice and experience to know how to handle whatever conditions you're in.

jky

[9D280]

+1 to Nos & Henry's descriptions.

To add to the soup, I trim in (but not fully) to get from 0 -> plane, then trim out until either the prop starts ventilatiing at the slightest excuse or the waves are getting too hairy.

Sounds wolly & imprecise? Yep it is, BUT as also said above, when it feels & sounds right, it probably is. As you trim out (slowly at first until you get the hang of it) you will hear the engine note change from labouring to "free singing".

To put this in perspective I retro-fitted PT to mine, and never got round to fitting the trim gauge sender to the engine -my gauge is still not connected & I trim purely by feel & audio.

So there's your excuse to go & play!

[jyasaki]

Originally Posted by 9D280

To put this in perspective I retro-fitted PT to mine, and never got round to fitting the trim gauge sender to the engine -my gauge is still not connected & I trim purely by feel & audio.

Mine came with a gauge, but the only time I look at it is when I'm verifying that the motor is up for skinny water or trailer recovery, or making sure I'm not doing something [else] visibly stupid. Usually when running I just go by how the boat is performing.

jky