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Whaler rolling
duf	#1  Posted on 05/06/13 - 1:27 PM
Member Personal Page Photo Albums Posts: 840 Comments: 9 Joined: 04/22/07	Just curious, what exactly is causing the phenomenon where at high speeds when you drop the trim down, or go to high speeds and don't trim the motors up the boat rolls. My 22's did it and of course i learned long ago to trim the motors up as i but on more speed. Sunday during a speed run on my new motors on the 25, trimmed the motors down looking for the sweet spot, and at almost 50 MPH the boat rolled hard to the right. Just curious what factors are in play to do that. It was a pretty aggressive roll. I would assume the only thing that would be effected would be the bow height, so whats giving the hard right roll? Duf
huckelberry145	#2  Posted on 05/06/13 - 4:49 PM
Member Posts: 401 Comments: 3 Joined: 03/10/12	My 15' 70 hp Yamaha was doing that because not enough of the trim tab was in the water while on plane. It was pulling hard to starboard when I had the motor all the way 4 holes up.
duf	#3  Posted on 05/06/13 - 5:43 PM
Member Personal Page Photo Albums Posts: 840 Comments: 9 Joined: 04/22/07	Well, i don't have trim tabs and its a very aggressive roll, so just wish to understand the physics that are causing it. I know its going to happen, got that, but am interested in the whys! Duf
bcoastal	#4  Posted on 05/06/13 - 6:13 PM
Member Posts: 291 Comments: 0 Joined: 08/15/12	I don't know if this is the same but I got a boat once that did that because it had the wrong size prop. But if I remember right the boat would pull the entire time while on plane.
huckelberry145	#5  Posted on 05/06/13 - 6:36 PM
Member Posts: 401 Comments: 3 Joined: 03/10/12	I'm actually talking about the adjustable tab on the antiventilation above the prop.
duf	#6  Posted on 05/06/13 - 6:54 PM
Member Personal Page Photo Albums Posts: 840 Comments: 9 Joined: 04/22/07	Not sure either gents, though i'm sure someone on here does. It's a very aggressive roll, and i'm sure someone, maybe with a 22 or larger Whaler has dealt with it. duf
jamesgt727	#7  Posted on 05/06/13 - 7:17 PM
Member Personal Page Project Albums Posts: 360 Comments: 0 Joined: 01/17/11	Duf, is it an occurrence you can predict and possibly video? I'm curious to know a which speed (less) that it does not happen. What type and brand, model steering system do you have? Do you have a picture you can show directly behind the boat facing the motors, and maybe a pic or description of the planing surfaces on the hull at play here?
Tom W Clark	#8  Posted on 05/06/13 - 8:35 PM
Member Personal Page Posts: 4280 Comments: 7 Joined: 09/30/05	Duf -- What you experienced is very similar to a sailboat broaching. When the bow is forced down into the water, as it might with the motors trimmed in with good stern lifting propellers on the motors, the buoyancy of the bow wants to float upward, but it is does not do so in a stable fashion; as soon as it tends to one side, the bow will accelerate in that direction. This is exacerbate by the high speed. The same thing can also happen with twin outboards that have too much toe-in. I doubt that is your problem given the Whaler Drive but you might check it just to eliminate that possibility.
Jeff	#9  Posted on 05/06/13 - 8:42 PM
Member Posts: 1987 Comments: 34 Joined: 04/02/05	Duf, The situation you are referring to is the work of gyroscopic rotational forces from the motor forcing the hull over. This problem is the most noticeable and common when operating a single engine vessel with the motor trimmed all the way in, thus forcing the bow to "plow" while on plane. Edited by Jeff on 05/06/13 - 8:43 PM 1993 23' Walkaround Whaler Drive
aeriksen	#10  Posted on 05/06/13 - 9:25 PM
Member Posts: 242 Comments: 0 Joined: 07/24/12	I just experenced the same on my seatrails, I attributed it to the rotational torque of the prop without enough trim as the bow came down and with the torque of the prop the left chine dug in and tossed me and to the right. My conclusion was improper trim at the speed I was going. Just my observation.
Finnegan	#11  Posted on 05/06/13 - 10:39 PM
Member Posts: 1926 Comments: 16 Joined: 05/02/08	In spite of having a fast 18 Outrage, and a fast 25 Outrage, I have never experienced this condition. My guess is that the situation is "bow steer". Mercury says:" Trimming engine in, in excess, can cause the boat to veer to the left or right (bow steer). They also say it can cause undesireable and unsafe steering conditions. With those high torque engines at high speed you might have driven the bow into the water too much, too fast. The situation could be exaggerated if the engines are mounted too low. You should be up in the 4th set of holes at least, maybe the the 5th (all the way up). Check your engine bracket design. It may have a provision for a tilt pin stop to prevent excessive trim in, like the older design engines had. A 10" long 3/8" SS bolt can be used (at least on mine it can). This will prevent excess/unsafe trim in, hence preventing the rolling you describe. Edited by Finnegan on 05/06/13 - 10:52 PM
awayland	#12  Posted on 05/07/13 - 3:24 AM
Member Personal Page Posts: 160 Comments: 0 Joined: 04/30/09	It's not a whaler but my 25' boat with an I/O will do this on a plane, outdrive trimmed all the way in and the trim tabs too low. It makes the bow dig and it takes an aggressive turn. 1970 custom 16 with 1999 Merc 2 stroke 90hp
EJO	#13  Posted on 05/07/13 - 9:08 AM
Member Personal Page Posts: 669 Comments: 6 Joined: 11/25/12	Duf I assume you have counter rotating setup with the two motors? It's what Tom said broaching or like finnegan said bow steer. A very dangerous condition as the boat can really roll over forward when the bow suddenly digs in instead of just rolling to on side. You must adjust trim and motor mounting height to keep that from happening when you want to keep using the high torque/HP motors you have. Skipper E-J m/v "Clumsy Cleat" a 2008 Montauk 150
Barry Bicknell	#14  Posted on 05/07/13 - 9:12 AM
Member Posts: 28 Comments: 0 Joined: 05/08/12	As already noted above, the hard pull to the right (not left) when a single outboard is trimmed all the way down/in is the result of gyro rotation force caused by the "prop rotation" and hull drag. This is NOT the case for twin counter-rotation outboards are used as they are counter acting the gyro rotation torque. The off-set to this gyro rotation torque is also as mentioned in another post above, "adjusted" using the trim tab found under the anti-cavitation plate above the prop. Turn the "back" of this trim tab in the "opposite" direction (left) as your pull is to the right. -Barnacle-
jamesgt727	#15  Posted on 05/07/13 - 9:36 AM
Member Personal Page Project Albums Posts: 360 Comments: 0 Joined: 01/17/11	I agree with the latest, I think its time to get some tabs. Keep the drives high and optimize with tabs. I have a ton of experience with 20'+ boats with single, twin, and triple engine boats. My latest CC had 24" K-Planes (snuck a pic on the bottom of my PP temporarily). I also noticed on you personal page that photo #8 down, shows your boat under idle power, engine turned slightly, and you boat appears to be leaning. Is that an optical illusion? Fuel shift? Boat not loaded and too buoyant with a high CG? Did you ever notice that happen?
CES	#16  Posted on 05/07/13 - 10:46 AM
Member Personal Page Photo Albums Project Albums Posts: 2681 Comments: 7 Joined: 04/27/07	When I ran a 25' CC Mako with twin 225's on it professionally, I would run the engine trim up to the point where it almost cavitates. It was at that point where the bow has risen enough at full power that it's wouldn't hook to the right. This was 20+ years ago.....but I'm sure the same principle still applies. Cliff 1966 13' Sport with a 1993 40hp Yamaha 2 Smoker
Tom W Clark	#17  Posted on 05/07/13 - 10:55 AM
Member Personal Page Posts: 4280 Comments: 7 Joined: 09/30/05	I own a 25 foot Whaler with twin 150 HP Mercurys on it. I've run it with both motors as standard rotations and then converted one to counter rotation. "Gyro rotation forces" have nothing to do with what Duf is describing, nor do the trim tabs on the motor (which Duf's motors do not even have)
TexasOutrage	#18  Posted on 05/07/13 - 11:32 AM
Member Personal Page Posts: 246 Comments: 1 Joined: 02/16/08	Duf, How rough was the water when this happened? Was there a following sea? Since you were running 50mph my guess is you were in the ICW with small chop. I have not experienced this in my boat. Perhaps there is too much weight between the center console and the leaning post...just kidding. Glad to hear you were not hurt.
jamesgt727	#19  Posted on 05/07/13 - 11:45 AM
Member Personal Page Project Albums Posts: 360 Comments: 0 Joined: 01/17/11	Tom, To clarify, I was speaking about transom mounted hydraulic trim tabs. Those are independent of the drive. Edited by jamesgt727 on 05/07/13 - 11:47 AM
Tom W Clark	#20  Posted on 05/07/13 - 11:49 AM
Member Personal Page Posts: 4280 Comments: 7 Joined: 09/30/05	James -- Yes, understood, others were not. No place for trim tabs on a 25 foot Whaler with Whaler Drive.