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Old 19 July 2012, 04:01   #21
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Quote:
Originally Posted by freyaflys View Post
re ssobol remarks and trim down, have spent last few days in light chop off Mull. A lot of porpoising greatly reduced by trimming right down as opposed to level trim, with no loss of speed and much happier passengers. My question is when is trim up ( above horizontal) useful ? Trim gauge may now be useful. Yes I know its useful to avoid shallow obstacles but when else?
You have discovered the "feel" comments made above.

Trimming up (and for the anoraks out here, I'm going to say this in a "touchy feely" sort of way) On my setup, trimming up "unloads" the engine, and so allows for greater RPM at the same throttle (you can hear the engine "running free"). This means more speed for less throttle, so conversley you can for a given speed throttle back a touch, in theory drinking a touch less fuel. (althoug hIhave yet to find enough open falt water to put numbers to this theory)

The down side is if you keep nudging it out it will eventually start ventilating at the slightest provocation. For my boat on flat water, somewhere slightly below there appears to be optimal. Show it some waves and it will be down "a reasonable way".

Like I said, a bit "touchy feely", but hopefully help to to compare to what you found?
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Old 23 July 2012, 16:47   #22
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thanks for that Uncle al
stuart
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Old 24 July 2012, 17:34   #23
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Trim gauge on my Merc 90 4Str gave up after a couple of years. I didn't need it as a glance behind would tell me where the trim was. The flat top of the engine gave a good indication.

My new Honda 90 is all sexy curves and flutes and I've no idea what the trim is without the gauge. I rarely go beyond 4200 rpm and at that speed I can trim up beyond the point where the trim rams reach 'full up' and the tilt ram takes over. This improves boat speed in calm water, but must strain the tilt ram and engine bracket as it's not supported each side, as with the trim rams.

Maybe as I get used to the engine the gauge will be less used, but at the moment I've marked the gauge with the dead level and max trim ram positions and it's a great help.

As Tim M (Wavelength) says somewhere in this thread, I think, the Destroyer responds instantly to the slightest trim change. Just a tiny touch of down is the difference between bone jarring and silky smooth.

I've plastered the trim sender with silicone grease in an attempt to keep the water out of the works, and just have to trust in Japanese engineering.
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Old 24 July 2012, 19:35   #24
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I find a trim gauge extremely useful. Without one the only way to tell whether the boat is trimmed correctly is to trim it wrongly then retrim it back to when it felt better. It may take more than one try to get it right so is an unnecessary task. Do you need one? No. Is it better with one? Undoubtedly. imho, as usual.
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Old 25 July 2012, 03:10   #25
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Quote:
Originally Posted by alystra View Post
I've marked the gauge with the dead level
I am at a loss as to when you would need dead level?
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Old 25 July 2012, 03:13   #26
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Originally Posted by jwalker View Post
I find a trim gauge extremely useful. Without one the only way to tell whether the boat is trimmed correctly is to trim it wrongly then retrim it back to when it felt better.
That is by far the most popular way of doing it right. Trim out until the ride starts to become a big jumpy, then trim back in a tad.

It is not uncommon to be constantly tweaking the trim and the conditions change slightly, to maintain a safe and comfortable ride. In which case you would be constantly feeling for the groove, in other words finding where it feels wrong and going back.
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Old 25 July 2012, 09:51   #27
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Quote:
Originally Posted by freyaflys
...My question is when is trim up ( above horizontal) useful ? ...
to avoid stuffin when blasting downwind in a chop

Jan

Sent from my iPhone using Rib.net
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Old 25 July 2012, 16:28   #28
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Quote:
Originally Posted by Channel Ribs View Post
That is by far the most popular way of doing it right. Trim out until the ride starts to become a big jumpy, then trim back in a tad.

It is not uncommon to be constantly tweaking the trim and the conditions change slightly, to maintain a safe and comfortable ride. In which case you would be constantly feeling for the groove, in other words finding where it feels wrong and going back.
Oh ya - otherwise you could end up in the sh1t.
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Old 07 August 2013, 19:14   #29
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How to trim?!

Hi everyone,

Thought I would ask here as there is some useful info in this thread. My current rib is 4.2m with 50hp and it has a double jokey seat in the centre and a seat at the bow of the rib. Its the first outboard I have had with power tilt and trim. I have had it a year now but only really played with the trim in the begging and to be honest I found my rib was best with it trimmed all the way in (down). Do you think I am correct? Maybe small ribs dont really need their tirm adjusting as much as bigger boats? If you get people's seating positioning correct do you need to trim?! Am I being naive?!

After reading guides tonight I think I will have another play when I next use my rib. I will accelerate onto plane (trimmed all the way in) and then once planing at a slow cruising speed I will trim out slightly and see if my revs AND speed go up. Is this the correct thing to do?

Thanks everyone!
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Old 08 August 2013, 01:45   #30
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Fitted a tachometer & a trim gauge to mine this year for the first time and was impressed with how much difference small amounts of trim made to the rpm on the plane. It's a Mariner 135 V6 and I trim in to get the 'hole shot' for skiing but out slightly to cruise at @3000 rpm.
I don't find the gauge accurate enough to be confident it's where I need to be & rely more on feel/sound to get the best out of the engine by adjusting on the move. Trimmed in 4500 rpm but soon goes to 5000 rpm when trimmed out slightly but this soon empties the fuel tank....
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