Trim Question (new to boating)

[ChrisWalsh]

This is going to sound dumb, but i just got my first boat and i want to make sure i know everything about operating it before i just go out and drive it. I recently replaced the Tilt motor on my boat it is an 3.0L OMC I/O i know the tilt is for actually lowering the outdrive to the boat, but i noticed the trim actuallt lifts and/or lowers the motor and the outdrive both at the same time, what is the trim exactly used for? thank you.

 

[The Fifth Lady]

Re: Trim Question (new to boating)

Just got my first boat this Spring and my learning curve has increased 1,000%! Welcome! Trimming is very important in getting your boat up on plane AND for maximing fuel efficiency. You want to increase throttle while trimming to get bow down initially and up on plane...then you want to trim so bow goes up to maximize speed, fuel, and comfort of ride. You will want to watch your RPMs and keep them the same while trying to increase speed.

If you have Trim Tabs, this is easy.

In any case, NEVER tilt the outdrive out of the water when running, as the water intake keeps the engine cool.

I recommend checking/ getting an Owner's manual, which will help you with lots of general usage type questions and more technical stuff also.

Also, get a buddy to brief you and go out with you the first few times, esp if you are in more than a lake.

GOOD LUCK

 

[wire2]

Re: Trim Question (new to boating)

On an OMC Stringer, (up to '85) the tilt is used to lift the outdrive for trailering. When running the boat, it should be in the full down position. If not, the ball gears wear VERY fast. The only exception is when navigating in very shallow water, it's ok to bring the tilt up a bit and drive it at low rpm's, (idle).
Trim on any I/O is to obtain lift on takeoff by having the prop push the boat up to get on plane, then trim out for more speed & efficiency. You will get a feel for it quickly.

 

[Don S]

Re: Trim Question (new to boating)

Here is a Mercruiser Owners manual that explains the basics of trim and tilt.
http://www.boatfix.com/merc/Owner/gas/86017101.pdf

Since this isn't an engine or drive mechanical problem, moving to Boat Topics and Questions (not engine topics)

 

[studlymandingo]

Re: Trim Question (new to boating)

i noticed the trim actuallt lifts and/or lowers the motor and the outdrive both at the same time

Could you explain this a bit more?
Is the engine inside the boat moving when you adjust the tilt???​

 

[wire2]

Re: Trim Question (new to boating)

Could you explain this a bit more?
Is the engine inside the boat moving when you adjust the tilt???​

Not the tilt, only the trim. In the tilt down position, the outdrive is held solid against the transom assembly of an OMC stringer. Operating trim "in" lifts the front of the engine, the swivel point is at the transom, and the outdrive trims in. Trim "out" lowers the engine. The transom assembly is not bolted to the boat's transom, but allowed to pivot on a rubber "boot"
It was done mechanically in early models, hydraulically in later years.
Trim and tilt were 2 separate and unrelated functions in a pre-Cobra OMC.

 

[ChrisWalsh]

Re: Trim Question (new to boating)

no, the trim lifts the motor and the outdrive at the same time, not the tilt. i needed to know what the trim it for. thank you for all who have replied so far.

 

[Silvertip]

Re: Trim Question (new to boating)

Tilt raises the outdrive (tilts it up) for trailering or to get across shallow water. Trim adjusts the attitude of the boat. You trim in to get on plane. Once on plane you trim out for best ride and performance. To understand the two straighten a paper clip. Then put a 90 degree bend in it (make an "L" out of it). Now turn 180 degrees left. When you adjust trim, you are raising or lowering the front of the engine on an OMC stringer. That action pivots the upside down "L" as a complete assembly. It adjust the angle of thrust and hence raises or lowers the bow of the boat (trim out and trim in respectively). When you use the Tilt function, you pivot only the leg (the downward part of the paper clip). The engine does not move. If you still don't understand, post back and I'll draw you a picture.

 

[aerwin]

Re: Trim Question (new to boating)

never run the outdrive partily up in shallow water!!! the drive always has to be down. the ball gears will wear out prematurly in not completly down. if the water is that shallow stay out of it

 

[wire2]

Re: Trim Question (new to boating)

never run the outdrive partily up in shallow water!!! the drive always has to be down. the ball gears will wear out prematurly in not completly down. if the water is that shallow stay out of it

Not to start an argument, but I've had an '84 Glastron 19' with an OMC 5.7 since new. My dock is in shallow water in a lagoon, 300 ft off the lake. I've made hundreds of exits/entrances with the tilt up a bit to keep the prop out of the mud, but never over 1000 rpm. I use it from May to October every year and have replaced the ball gears only once in 23 years. The 2nd set are about 40% worn now but they show no unusual wear pattern.
I did recently see a set of ball gears that were very worn on the tips as well as the forward surfaces, that would be a result of running at speed with the tilt partially up.
Someone forgot or didn't know.
That can't happen to me. I have a Holley aluminum intake, 1.6 roller rockers and double wall stainless headers. If I do happen to forget the tilt being up a bit, it comes down with a thud when I punch it. The torque easily overcomes the tilt clutch. It planes in 1 second.

 

[ChrisWalsh]

Re: Trim Question (new to boating)

Thank you everyone who replied to my post i appreciate it and thank you Silvertip for the paper clip idea, (it really did work on explaining how it works) i appreciate it.