25 tollycraft unstable in chop

[Charlie_s50]

I just repowerd a 1981 tollycraft 25. It has a Volvo Penta dps outdrive with a marine power 350 Chevy engine. When we took it out for the test run in the inlet there were 4ft waves and it cruised through them no problems. When we took it out this weekend there was a slight wind at most a 2' chop in places and when on step it would all of a sudden pull hard and try to roll over. Changes in trim and direction didn't seem to make any difference. Was only stable after I backed off of step. Other smaller lighter boats were passing me on step no issues. Boat cruise speed is about 26-29mph. Wasn't stable unless I was under 12mph and plowing water. Also the boat didn't want to nose down unless I had the drive all the way down and the trim tabs pretty far down also.

 

[Scott Danforth]

your going to have to look at your hull

you may have been riding on top the wave and fallen off

do your trim tabs work? drop both of them evenly to try to induce some drag to keep the bow down which should help

 

[Charlie_s50]

The waves were pretty small to have fallen off of and I had to run drive all the way down with the tabs down. What should I look for with the hull? Also had about 50 gal fuel on even weight with passengers and not much extra weight.

 

[mr 88]

You state you repowered it , Did you own and use the boat before that ? Or did you buy the boat without a sea trial ? Sounds like it/ you upgraded it to a duo prop ? Are the props the correct size and diameter for your hull ? Reaching rated max rpm of engine ? Is the hull a flybridge model ?

 

[Charlie_s50]

So I bought the boat non running with the duo prop already installed. The props are 2 step too aggressive it has d7 and needs a d6 prop set. And yes it is a flybrige model but there was not any weight up top.

 

[mr 88]

Even with no "weight up top " the flybridge itself weighs at least a few hundred pounds if not more depending on how it was constructed ,A 25' flybridge boat with a single engine is going to have that instability .Your center of gravity is affected by this and will be magnified the higher the bridge is from the waterline. Not sure where you got info about the prop setup but if that is the case I would start there to see if that helps your issue.Any weight that you can shift from above the waterline to below may help as well.

 

[Charlie_s50]

I get the fly brige adds a little weight up top but I've only owned single engine boats. This Theis the first one with a counter rotation drive tho. water ithat day was something I wouldn't of slowed down for in my smaller Sea Ray I would of just went through it at 30mph+. The boat doesn't feel top heavy on the water from what I can tell the fly is built pretty light as a bolted on unit and the hull is over 1/2 thick glass. I am going to talk to a VP dealer on the props. If I'm correct the D series is a straight spline and the DPS-B drive has helical splines. I'm wondering if he had a bargain set of props re hubbed? If I can I'll post pictures tomorrow.

 

[pole position]

Sounds like the tabs and drive down that the bow was digging in.Did you try tabs up and drive trimmed?

 

[Charlie_s50]

So with the tabs and drive up my nose was as high as Willie Nelson I kept trying to find a happy setting and drive all the way down was the best