What is the reason for trim rods?

[Stamey]

I just bought an '89 Mariner 75 and I notices that it has trim rods, in addition to the trim cylinders. What are these for, and why are they necessary?

Thanks,
Chris

 

[Silvertip]

Re: What is the reason for trim rods?

Trim allows the operator to adjust the attitude of the engine to enable getting on plane and then adjusting again when on-plane for the proper boat attitude. If the engine is tilted too far in it forces the bow down and the boat plows. Too far out the boat may ride bow high and porpoise. Happiness is somewhere in between. There is no one size fits all when it comes to trim settings. Trim adjustment depends on the hull design, the amount of power available, the load in the boat and water conditions. Get in the boat, and experiment with trim settings. Trim doesn't do much when you are just poking along off plane so get on plane and experiment. Pay attention to the seat of your pants and listen to the rush of the water. When you achieve proper trim setting, the boat will pick up a few MPH and the rush of the water will suddenly quiet considerably.

 

[Stamey]

Re: What is the reason for trim rods?

Thanks, but I wasn't asking about what "trim" is, I was asking why this outboard has "trim rods" in addition to trim cylinders. My Force 70 only has trim cylinders, as well as my Mercruiser.

Thanks,
Chris

 

[rodbolt]

Re: What is the reason for trim rods?

its cause your nomencature is wrong.
you have two trim rams and a tilt ram.
you also have a constant volume constant pressure single speed hydraulic pump.
thats why trim is so much slower than tilt.
for trim the fluid goes under two pistons doubling the force but at half the speed.
once the trim rams are fully extended all fluid pressure is now forcing the single tilt ram up.
its also why mercruiser and some mecurys with the two ram setup used a trim limit switch so the operator had to change buttons to raise the engine above the trim range.
the 3 ram units use a relief valve that while underway wont allow hydraulic pressure to tilt.
it was a better mouse trap, however every time a better mouse trap is built mother, nature makes a dumber mouse.
,

 

[Stamey]

Re: What is the reason for trim rods?

OK, thanks. I thought my terminology was correct because I used what the parts manual called those rods. Perhaps that's not the generally accepted term.
Thanks for the info.

Chris