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Old 30 September 2011, 13:38   #1
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RIB leaning to port(a lot) under power

Got a Rib last week its a Humber Scavenger 5.2m with a suzuki 115hp.
Went brill for about an hour moored up and then on journey back when going onto plane you can feel it start to lean to left as power increases lean becomes worse and worse and RIb is very unstable.Have drained all water out as I thought it may be that, have looked at everything , the anode above prop hasn't moved, engine not moved and just cannot think why its doing it... any help would be realy appreciated,as its just not useable as it is now.
Thanks
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Old 30 September 2011, 14:06   #2
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Whats a Humber Scavenger? Not heard of one of them before. Pics please

My destroyer is prone to a little heel but bringing the trim up a little soon sorts it in most cases. Sometimes it is exaggerated by a strong side wind too. How much offset is the motor rigged with?

Mark.
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Old 30 September 2011, 14:27   #3
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Whats a Humber Scavenger? Not heard of one of them before.

I was thinking that too.

I was also thinking 115hp is rather a lot for a 5.2.
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Old 30 September 2011, 15:28   #4
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Humber Scavenger
never heard of one, and we've driven for them at boat shows for years. Not an attractive name for a boat model
is the outboard in the middle of the boat or offset.
Piccie of underside of hull would help for i.d.
Strange if it was ok outbound but not back, suggests a variable such as trim angle or a particularly large crewmember
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Old 30 September 2011, 16:57   #5
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I'll take pictures next week, the conundrum is that it was fine on way out ,left moored for an hour then problem set in.
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Old 30 September 2011, 17:13   #6
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I'll take pictures next week, the conundrum is that it was fine on way out ,left moored for an hour then problem set in.
is the drain bung sealing properly?
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Old 30 September 2011, 19:02   #7
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If you try to rock the motor while on the trailer, is there a lot of play?
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Old 30 September 2011, 22:22   #8
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Thanks I'll check
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Old 01 October 2011, 16:09   #9
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I had a single 275HP RIB that was bad for this ... and it was a really annoying problem because if you left a wave, the boat just wouldnt fly straight .. and kept slamming into waves on the port side.

Trim could sort the ride (to a degree) but it couldnt fix the wave jumping

I tried ballast and that helped, but didnt do much for fuel consumption, in the end I think it was down to an offset problem and the sheer power and torque of the motor.

The trouble is without putting more holes in the transom, you dont really want to move it, so I looked at 'a' trim tab .. but never did it

On this particular boat.. the D section delaminated off the port sponson .. mind you it WAS a Northcraft ... (am I a slow release for Northcraft woes ? .... oh yeah )
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Old 03 October 2011, 04:16   #10
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Well I have had this. Engines act like gyroscopes and can cause the boat if light enough to roll to the right/left depending on rotation,

if yo dont have much hull in the water the porp will make the boat roll to the right.
as its bighting the water and the boat is in the air( well most of it)
so a light 5.2 rib with a big 115 on it will roll.
abviously the roll depands on the way the engine/prop rotates
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Old 05 October 2011, 02:16   #11
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Thanks for replies

Hi All
Your comments are very much appreciated,BUT this leaning to PORT did not happen when I took RIb out for a 1 hour run of approx 25 miles, all was fine, we moored for 45 mins and then on return journey the lean was there straight from setting off...very odd.
I'm just back from long weekend away and will get ochacking all you r ideas
thanks again
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Old 05 October 2011, 02:31   #12
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Hi All
Your comments are very much appreciated,BUT this leaning to PORT did not happen when I took RIb out for a 1 hour run of approx 25 miles, all was fine, we moored for 45 mins and then on return journey the lean was there straight from setting off...very odd.
I'm just back from long weekend away and will get ochacking all you r ideas
thanks again
Which way was the wind blowing? most boats lean into the wind and the wind could have been balancing the boat going out and making it worse on the way back in? Either that or something else changed.
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Old 05 October 2011, 03:05   #13
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Is it still doing it since you drained all the water out? Shouldn't really be water in the hull so sounds like you have a leak?
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Old 05 October 2011, 03:28   #14
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Got a Rib last week
So is this the first time out? Mine did that with a 55, like to the point that with three heavy people on the uphill side it still wouldn't go level. Only ever happened above 21 Knots.

Wasn't 'till the engine died & I took the opportunity to turn it over & remove 30 years worth of antifouling that I discovered that the hull had been repaired by one of it's previous owners.

The "as designed" side had a slight concave, presumably to give a bit of lift to the back end. Problem was the repair (at the rear, immediately in front of the transom) was convex. Got it ground back to symmetrical, problem gone.

As you presumably have a used boat, if the hull has been painted or antifouled, it might be worth doing a compare & contrast port / starboard at the stern. (& if not obviously symmetrical, scrape some paint to check for repair) Its not hugely likely, but worth eliminating before you start mucking about moving engines, as it's just a case of a good look.
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Old 05 October 2011, 04:03   #15
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What were the sea conditions? Single engined boats tend to list due to prop torque, especially when coming off waves as the prop is usually the last bit out of the water. If you had waves on your "listing" beam on the run out, the sea would have counter-acted the prop torque, effectively pushing the boat back upright. On the way back, on the opposite beam, it would have compounded it.
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Old 05 October 2011, 07:16   #16
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Unless you re fueled you've reduced the weight/ballast as well on the return journey. You say 25 miles so you will have burned approx 25 litres of fuel, this may well have changed the set up, especially if you altered the trim when you moored, set off again.

My Rib will heel considerably, if trimmed in too much, I'd certainly try trimming out first to see if that cures the problem
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Old 05 October 2011, 13:00   #17
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Of course all this assumes you dont have a leak at the cone on your port tube thats letting water into the port tube whilst under way, thereby adding the weight and list ... it would be rare,.. but I have had that problem ,.. which ultimately caused the tube to explode .. that was a fun story Ive yet to do a ribnet elaboration of
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Old 16 July 2012, 09:25   #18
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Hi chaps, old thread I know, but we have just setup a Humber Ocean Pro 7.5 with a 2.8 beam, Honda 250hp which is torquing off to the left badly. the engine is offset by 1.75 inches and the trim skeg is also about 5 degrees off to sbd.

Has anyone got any data on this boat? Any suggestions before we start drilling more holes!
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Old 16 July 2012, 09:54   #19
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Hi chaps, old thread I know, but we have just setup a Humber Ocean Pro 7.5 with a 2.8 beam, Honda 250hp which is torquing off to the left badly. the engine is offset by 1.75 inches and the trim skeg is also about 5 degrees off to sbd.

Has anyone got any data on this boat? Any suggestions before we start drilling more holes!
Engine height correct?
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Old 16 July 2012, 11:48   #20
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Quote:
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Engine height correct?
Thats where I'd start.
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