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Old 21 October 2018, 06:38   #1
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Trim settings

I've heard a lot of people talking about trim and tilt here in the forum so said I'd look into it myself as I notice the sib doesn't really pain on the water.

So, the outboard has 4 trim settings, manual.

1. Started off with the hole furthest from the boat. This angled the outboard up alot, touched the throttle and it moved, gave it a little bit more and started racing and going no where. Onto number 2.

2. The angle looked alot nicer sitting on the boat, give it a little throttle and you could feel the sib starting to come up on the plane and give it a bit more and we are back to revving so onto 3

3. The angle of the outboard is now facing downward but will keep on throttle the whole way thru the revs but is forcing the front of the boat into the water. 4 is pretty much the same but a little worse!

To be fair it's a big sib at 4.5m and it is only a 15hp, are my expectations to high to do the up on the plane? Or am I do something wrong?
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Old 21 October 2018, 09:40   #2
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id try all the way in on the first hole with a bag of sand or someone sat right at the front in the bow
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Old 21 October 2018, 13:34   #3
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4.5 is a big boat for a 15 hp IMO
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Old 21 October 2018, 15:16   #4
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Quote:
Originally Posted by beerbelly View Post
id try all the way in on the first hole with a bag of sand or someone sat right at the front in the bow


I think he is saying that on the lowest two positions the bow is too low, so not sure it needs that and sand.

If I understood correctly he either wants second highest pin and weight further forward OR he probably needs pin 3 and perhaps fuel/load further back? Although Iím not sure what bow too low, revs properly the full range and not planing would be like, what speed do you get?

Itís possible that a different prop could make a difference as you are trying to push a big boat with little power, but before you start doing anything make sure you have everything inflated correctly etc.
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Old 21 October 2018, 16:22   #5
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Quote:
Originally Posted by Poly View Post
I think he is saying that on the lowest two positions the bow is too low, so not sure it needs that and sand.

If I understood correctly he either wants second highest pin and weight further forward OR he probably needs pin 3 and perhaps fuel/load further back? Although Iím not sure what bow too low, revs properly the full range and not planing would be like, what speed do you get?

Itís possible that a different prop could make a difference as you are trying to push a big boat with little power, but before you start doing anything make sure you have everything inflated correctly etc.
oops obviously never read it properly I thought he was riding bow high and not planing
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Old 21 October 2018, 17:03   #6
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Another thing to consider is getting the engine set to the optimum height, on my Suzuki 20hp the cavitation plate was recommended to be 50mm from the bottom of the hull and this would be a starting point, you can't just drop an engine on a transom and expect it to be right. I found small changes had a big impact, lower and there was less aeration on those higher trim settings but also much worse performance.

Larger SIB's tend to flex and bend in the middle and things would only get worse if you were to have more power. Under some trim settings and boat loading I had an air 'bubble' build up under the hull which would eventually pass through to the prop making the engine rev, cycle repeating every 10 seconds or so. Very annoying. No substitute for a rigid hull and power trim!
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