Re: What's causing the boat to list?
 

"At around 45 mph, the boat dives to port and almost seems to want to roll over. Very Scary"

AGREED! [img]images/icons/shocked.gif[/img]

Re: What's causing the boat to list?
 

Sounds differant.. What size motor and what is the rotation? It sounds like the fuel tank is helping to keep this from happening and as you burn fuel the boat gets lighter and it wants to roll. Have you adjusted the anti hook fin on the lower unit?, is the motor straight on the stern(up and down). Check the hull too. you may have a cup in it .. find a long straight egde and place it in the hull and look for cups. Motor too high?.. more input!!!1

Re: What's causing the boat to list?
 

and thats with a single tab down to compensate

Holy Mackeral ! Looks like pipes has bout' got everything covered,I'd also say cupped.Fuel tank can't really shift,But a baffle can break allowing the fuel to go on one side.?.
Kinda remember My ol' girl(20 MA) listing a lil to port,trim tabs took care of it if "HOOVER" wasn't aboard.Dog biscuit to the starboard bow & Instant ballast !
Scream'n Reels' [img]images/icons/cool.gif[/img]

Re: What's causing the boat to list?
 

Hey Pipe - where is the anti hook fin? I get a slight list to port when running around cruising speed - I assume it is from the rotation of the prop.

Re: What's causing the boat to list?
 

Pipe Dreams, thanks...I've got a 1998 Merc 175 Offshore, with a four blade stanless prop. My mechanic buddy said to adjust the fin if the wheel/boat pulls to one direction. This thing literally dives to port. If the hull has a "cup" in it, what could cause it and how do I fix it?

Capt Brad, I had two healty size people sitting on the starboard side and it didn't quite cure the problem. At slower speed its more managable, but when I have 30 miles to run, I gotta move.

Mark ...scary ain't the word

[ June 03, 2003, 05:41 PM: Message edited by: 84 SeaCraft ]

What's causing the boat to list?
 

Hey all, I put up a post a while back about my 20 MA listing to port while underway. After I ironed out the bugs with the Bennett trim tabs, it seemed to help. But the problem is back and seems to be worse. At around 45 mph, the boat dives to port and almost seems to want to roll over. Very Scary, and thats with a single tab down to compensate. And the problem seems to get worse as the gas tank begins to empty. Could the tank have shifted? Any ideas, cause I'm out of them?

Re: What's causing the boat to list?
 

84
They make a Torque Tab (T-H Marine) It helps to eliminate some of Your right hand steering torque.Screws on the bottom of Your hull.But if You had Tabs down , I don't think this is Gonna Help !! Did You check Yet & see if Your Cupped.I'd like to follow this one thru.NOT that I want this Problem (Or Expecting)My bet is Your engine is not PERFECTLY straight up & Down.The faster Ya go the More list/twist You'll get .
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Scream'n Reels' [img]images/icons/confused.gif[/img]

Re: What's causing the boat to list?
 

Well... I've seen a hook caused by many things. Most common is from sitting on a trailer that was not adjusted right. Too much of the boat hanging off the back unsupported. Thus caving-in the last 2 to 3 foot of the boat, making a reverse trim tab to say. This will make the stern lift or in your case lay over at speed. If the boat hasn't been this way long it may come out just by reblocking the boat on the trailer to hold the boat the right way or use a bunk trailer. You may have a soft spot in your hull and underpower the hull will buckle causing the list. I would put a straight edge on the hull and look for cups in the hull, they will be large in size and width. Once you find it then you can figure out what caused it and then how to fix it. I know the hook fin is for taking out feed back in the steering, but I've seen it work for list to a point. Does this happen with the motor trimed up or down..Do you trim your motor up and use the tabs?. I had a 25 grady that would roll at speed like you say. Though watching someone else run the boat for me and riding on another I notice that the motors where kick under when trimed down. I moved the pin up one hole and the boat never did it again. Your motor may be causing the problem try move the motor down one bolt hole and put the trim pin back one hole so the motor doesn't kick under as far and use the tabs to bring the bow down. you could be running to flat and the boat is chine walking and falling over to port because of the motor rotation.

Re: What's causing the boat to list?
 

Eric,
That fin is located on the lower unit on the underside of the trim tab. It can be rotated to counteract prop torque.

Re: What's causing the boat to list?
 

Pipe Dreams...I'll check for the cupping. The boat is currently on, and has been for the last two years that its not in the water, on a bunk trailer. This may be a dumb question but should the cup appear on the port or starboard side. And if there is a large cup, how can it be corrected?

Re: What's causing the boat to list?
 

Don, Thanks for getting back to me. I checked the hull with a four foot level, and nothing unusual. The boat is sitting on a bunk trailer. I measured the motor mount, 33 inches from port to motor mount and 32 inches from starboard side to motor mount. Could that one inch offset cause that much of a problem?

Also, the boat settles down with a full load of gas, only as it empties does the problem get worse. The tabs don't completely push it over, and if I trim it too hard with the tabs it just dumps the bow down and still dives to port. Craziest thing I've ever seen. Regardless of the trim positioning of the motor, the problem is persistent. It is mounted on the highest hole on the motor mount, no pin on my Merc. And its a 175 so no problem with power, it will top out near 50 mph. Any other ideas? Also it has a four blade prop. and a big T-top on it, but I don't think that would cause the problem. Jason [img]images/icons/confused.gif[/img]

Re: What's causing the boat to list?
 

Like Don said there is a good chance the bottom developed a hook to it causing this problem. It is hard to find and is best done by someone that knows what to look for. Most of your fiberglass shops can make this type of repair.

Re: What's causing the boat to list?
 

Thanks Scott - much appreciated. I will try adjusting slightly.

Re: What's causing the boat to list?
 

You have a big motor for that size boat. The newer motors hp is rated at the prop. That is a lot of torque coupled with a four bladed prop (you do not mention dia. or pitch but I assume it may be around 14x19 maybe somewhat less). Stainless props do not flex too much which is why they are great for heavier boats, I assume you have a SS prop too. The bottom line may be that you have too much prop for your boat. Most runabouts that have clockwise rotation props also have the driver sitting on the starboard side of the boat. This counteracts the torque trying to rotate the boat to port (around the axis of the propeller) CCW rotating props have the driver sitting on the port side of the boat. CC's have the driver along the centerline of the boat so now you do not have the weight of the driver to balance things out. The engine being off center and the T top may make a bad situation worse. Also check to see if you have any water in the bilge. Water weighs about 8 pounds per gallon, so it does not take much to add a lot of weight to one side if it shifts (I doubt this is your problem but I have seen some really odd things). Try using a three bladed prop if you can get hold of one. Good Luck!