Poor Engine Trim - Help. - Page 2

C-NUMB · 01 October 2011, 18:30

Quote:

Originally Posted by Dirk Diggler

Still looks to low to me!

Same opinion!

thomas · 01 October 2011, 20:06

Thanks guys, went out today and there was a big improvement but I think I may knock it up another hole as there was still a bit of splashing but no way near last time.

Engine let go again though, real pity, only one cylinder this time so managed to limp home.

Good news it she likes it so much she wants a 5.5m, so it's gone from being my toy to our toy, looks like the raggie will have to go.

Chris · 01 October 2011, 20:45

Hi I would raise the engine so that the plate above the prop (anti ventilation plate) is about an inch above the bottom of the transom, you should notice quite an improvement in performance as it was very low before so would have been causing a lot of drag..

Oscarguitar · 03 October 2011, 09:43

Ckeck out this link.

This is for a Verado which have quite a big set back but the anticavitation plate height is valid for all set ups.

Propping correctly & how to test props.....

There are some pictures to give you an idea of what good looks like.

thomas · 03 October 2011, 10:07

Good info, thanks, I'm going to raise it again this morning.

If the anti ventilation plate is too low could this cause a problem with the cooling intake and then cause my engine to develop problems? I'm not just clutching at straws to diagnose my engine fault but me outboard engineer said it could be a possibility.

9D280 · 03 October 2011, 10:13

I also notice you have a reasonably raked transom. Your trim pin is in the bottom hole. To put this in prespective my old SR (and the humber) both have a transom rake similar to yours. The SR had the (non PT) engine sat on the second top hole, and I have the pin about halfway on the Merc (stops me / visiting drivers trimming in too far by accident)

Once on the plane I slowly trim out 'till the prop starts letting go & trim it back in a touch......

Dirk Diggler · 03 October 2011, 10:14

Quote:

Originally Posted by thomas

Good info, thanks, I'm going to raise it again this morning.

If the anti ventilation plate is too low could this cause a problem with the cooling intake and then cause my engine to develop problems? I'm not just clutching at straws to diagnose my engine fault but me outboard engineer said it could be a possibility.

Sounds like you need to change your outboard engineer!

Poly · 03 October 2011, 11:05

Quote:

Originally Posted by Dirk Diggler

Sounds like you need to change your outboard engineer!

If those were his exact words then Dirk's advice seems fair! I can't see how putting an engine deeper would cause a cooling water problem - but if this is the engine problems you refer to:

http://www.rib.net/forum/f36/selva-y...out-44210.html

Then I also can't see it being related to overheating!

I wonder if he said/meant with the engine deeper in the water the back pressure in the exhaust will be higher, which can make it difficult to idle (if set up at shallower depth)? Not sure if you are THAT deep though.

9D280 · 03 October 2011, 11:38

Too high & the intake will be out the water, but as a good chunk of your prop will also be wrong side of the surface, it's not really going to be an issue.....

For what it's worth, here's a pic of mine at about 20 knots:

http://www.rib.net/forum/attachment....6&d=1312188943

thomas · 03 October 2011, 12:12

Now my keyboard's broken!!

My engineer is pretty knowledgeable and does a lot of write ups in the mags and most people round this way can't rate him highly enough so will stick with him for now, I've had it idling perfectly in the wheely bin this morning and will try it in the water one evening this week.

I've raised it as high as I can, I think it still looks a little low compared to all the images I've seen but I've run out of holes on the bracket and transom so it will have to do, if it improved half as much as it did last time then I'll be very happy - but I will have to build up the transom to support it.

If I move the pin then how do I set the trim to know where it is - so the gauge is correct?

9D280 · 03 October 2011, 13:27

At this stage I wouldn't worry about fine tuning the gauge - I bet there will either be an adjuster screw on either the sender or the dial to set "bottom". All that will happen at the moment when you move the pin is that the needle will stop at "not quite full down". If the pin movement solves the spray problem at "full down", then opost back & we can work out how to recalibrate the gauge

I don't have a gauge on mine, I just use the pin to let me know it's at the bottom (audible "thud" & trim motor souding different!), and use the sound of the engine & feel of the handling to tell me when it's in the right place when trimming out.

Granted my engine was manual trim when I bought it - one of these days it might sprout a gauge!

two stroke mick · 03 October 2011, 16:02

I have a valiant DR 490 the bigger brother of your boat,

I would not adjust the trim in angle. These boats can be bow light and benifit from been trimmed in hard when heading into a head sea . There is an 13 degree rake in on the transom. This would appear to be more than most ribs

TSM

thomas · 12 October 2011, 15:19

Thanks for all your help on this one guys, we went out earlier and there was a big improvement, I reckon it could still go up a bit but the difference in speed is incredible, the engine is also running much better with no dramas.

This was taken at about 13 knots, just on the plane but it was too choppy for my little boat to be too adventurous.

9D280 · 12 October 2011, 16:30

Cool.

That will lift out further as you speed up & the boat rises. For what it's worth, the pic I linked to earlier on was taken on a flat day with me using my other hand to cling to the A- frame (& foot wedged in under the other side) having warned my friend on the helm not to pull any stunts....

So how many pins out were you, or was that just on the ram?

thomas · 12 October 2011, 17:04

Mine was a screen shot of a video, just held out my phone and hoped one frame would be ok.

I've left the pin in the bottom one, if I trim up slightly at low speed the bow comes up and on the plane it's perfect with the needle showing level - my next thing is to load up the front with an inflatable water tank as I have a heavy engine with the console and bench seat most of the way back, should also make it more stable with a bit of ballast.