Boat keeps porpoising.

[Jimwhall]

So, I’m enough months post op that I have been able to drive my 2016 Four Winns, with a 4.3 MPI.

The issue I keep running into is that I can’t stop it from porpoising unless I am trimmed all the way down. Is this normal with the engine in the back?

 

[poconojoe]

Does it ever get up on plane and flatten out?
Has the boat always behaved like this or is this a new to you boat?

 

[Jimwhall]

Does it ever get up on plane and flatten out?
Has the boat always behaved like this or is this a new to you boat?

It will get on plane and flatten out; but only if I'm trimmed all the way down.
You are correct; it's a new to me boat; and I've only been able to have it out a few times due to surgery. I'm wondering if it's somehow I have it loaded up. But yesterday it happened with just my wife and I and a full tank of gas.

I'm a little surprised; my old '95 Sylvan acted this way but the hull was very light, and all the weight of engine and fuel were in the back. I ended up putting trim tabs on it that helped. I was thinking that the Four Winns might be different though; the weight distribution *seems* better (though I don't know where the gas tank is) and the hull form is more complex.

My expectation was that I should be able to run with just people in it; some in the bow, some in the cockpit, about half trim and have it bounce over waves but stabilize after that.

The full tale of the tape of the boat:
2016 Four Winns SS with a 4.3 mpi, 3 blade stock prop 21 pitch 14.5 diameter.

Could going to a 4 bladed prop help by adding more lift?

 

[briangcc]

"My expectation was that I should be able to run with just people in it; some in the bow, some in the cockpit, about half trim and have it bounce over waves but stabilize after that."

Umm it doesn't work that way. The boat tells you where your trim needs to be. I set my trim to 1/2 on any of my boats, and I'm porpoising all over the place. Usually about 2/3rds to 3/4 trim down is where all my boats like to be - regardless of load.


As for your fuel tank....its probably in front of the engine. If you pop open the engine hatch, trace the fuel line. Bet its darn close to the engine bay - shortest path, least likely to chafe a fuel line.

 

[Scott Danforth]

the trim setting is dynamic and controlled by the operator depending on what the boat needs based on speed, load, condition, wind, etc. there is no set it and forget it. Ron Popiel did not invent the trim.

if people sit in the back, more down. if people sit in the front, more up.

that being said, every boat I have ever had with power trim (regardless of OB or I/O). for the hole-shot, all the way down (in), mash the throttle, as the boat is climbing out of the hole , start raising and as it flattens out, continue raising until it starts porpoising. then drop it down a bit until the porpoising stops (sweet spot). I never look at the gauge unless something goes awry or I need to go in skinny water

as you come off plane, drop the drive for the next hole shot.

 

[poconojoe]

It's possible a prop change may help. I'm no expert on props, so l won't even begin to guess.
Hopefully the experts will chime in soon.

Are you giving it enough throttle to get it out of the hole and on plane? You need to goose it until it levels off, then you can lower the throttle to find the sweet spot to keep it on plane.

My 18.5 ft. bow rider also has a 4.3. It has an Alpha 1 Gen 2 with a 3 blade 14 inch 23pitch aluminum prop.
Different boat, but may be similar, I don't know...

I give it a decent amount ( maybe half) of throttle and it will porpoise for maybe 5 seconds before it levels off. I can then reduce the throttle and keep it on plane at about 23 mph.
I have to do this with the drive trimmed all the way in (down). I don't think I'd get there as quick and stay planed if it were not trimmed that way.

 

[Jimwhall]

"Umm it doesn't work that way. The boat tells you where your trim needs to be."

"the trim setting is dynamic and controlled by the operator depending on what the boat needs based on speed, load, condition, wind, etc. there is no set it and forget it. Ron Popiel did not invent the trim."

Thank you everyone;
So what I'm getting is that I'm not necessarily doing anything wrong, nor is there anything necessarily wrong with the boat; it's just weight distribution/weather/wind/waves/towing that determines where the trim should be. And thank you for the Ron Popiel reference Scott. THe way you drive is also how I approach my hole shot.

 

[Cortes100]

The fuel tank is right in front of the engine, center of the floor.
With your model boat, I found the trim super sensitive, and could not use as much trim as my previous boat. I had the same experience and thought something was wrong. But with some more seat time, I quickly found that happy spot. I wouldn't even look at the gauge, I could just tell by the engine sound and ride. Try and go out on a nice calm day, and fool around with the trim, and you'll hear / feel the changes. I don't think anything is wrong with your FourWinns, just have to get used to the new ride.

 

[Dave1027]

Adding a hydrofoil to the outdrive may help.

 

[dan02gt]

Since no one else has suggested it I will. Trim Tabs! If you want to be cheap Smart Tabs will help drastically for sub $200. If you want lots of control go with helm adjustable.
I had a 19’ Stingray that would beat you to death and was slow out of the hole. Bennett M80 sport tabs 100% transformed it!

 

[poconojoe]

I don't mean to hijack the thread.
But, the talk about beating you up (rough ride), got me wondering. Can trim tabs help with that?

My 2003 Bayliner 185 bow rider 4.3L can get a bit rough when running on plane, due to chop from wind and wakes.
I just figured it's a normal by-product due to the shape of the hull and rough water. It gets so uncomfortable, the women need to support their breasts!
Would the ride improve if I added trim tabs?
Would the boat cut through the waves better instead of slamming down after hitting a swell or wake?

 

[dan02gt]

I don't mean to hijack the thread.
But, the talk about beating you up (rough ride), got me wondering. Can trim tabs help with that?

My 2003 Bayliner 185 bow rider 4.3L can get a bit rough when running on plane, due to chop from wind and wakes.
I just figured it's a normal by-product due to the shape of the hull and rough water. It gets so uncomfortable, the women need to support their breasts!
Would the ride improve if I added trim tabs?
Would the boat cut through the waves better instead of slamming down after hitting a swell or wake?

Yes you can use them to force the bow down harder so it cuts through the chop better.

 

[Jimwhall]

Since no one else has suggested it I will. Trim Tabs! If you want to be cheap Smart Tabs will help drastically for sub $200. If you want lots of control go with helm adjustable.
I had a 19’ Stingray that would beat you to death and was slow out of the hole. Bennett M80 sport tabs 100% transformed it!

I have smart tabs on my old boat. When my buddy went out on it he was shocked at the hole shot.

Still, I don't have the money for helm adjustables; and honestly don't want to drill into the hull of this one. It's still new and pretty to my mind.

 

[Scott Danforth]

Adding a hydrofoil to the outdrive may help.

No....No....No

 

[poconojoe]

Yes you can use them to force the bow down harder so it cuts through the chop better.

Thanks! Good to know.

 

[dan02gt]

As

I have smart tabs on my old boat. When my buddy went out on it he was shocked at the hole shot.

Still, I don't have the money for helm adjustables; and honestly don't want to drill into the hull of this one. It's still new and pretty to my mind.

It gets easier after the 1st one lol. My Stingray was only 2 weeks old and still had the new boat smell when I installed them. It was either drill holes or get a different boat. The ride was that bad!!
I put Bennett Bolts on my Chaparral 226 SSI after owning it for 2 years and even though it rode good without them, they still made a big difference and I wish I would have installed them sooner.

 

[Stinnett21]

I know Four Winns is a decent builder but you never know. Get a long straight edge and place it along the undersides of your hull near the back in several locations. Is the hull true? Very common cause of your problem, more common with aluminum, but not unheard of in glass. Could be why the PO sold it.

 

[Jimwhall]

I know Four Winns is a decent builder but you never know. Get a long straight edge and place it along the undersides of your hull near the back in several locations. Is the hull true? Very common cause of your problem, more common with aluminum, but not unheard of in glass. Could be why the PO sold it.

It's true; except at the back where they have 'cut outs' that is supposed to help the hole shot.

It isn't a super bad issue, I was mainly just curious. I'd read in the owners manual about how you can trim up and get 'optimum fuel economy and speed' but I never get to what they show in the diagram. I'm guessing there is some 'in optimal conditions' subtext in there that isn't mentioned.

 

[Jimwhall]

It gets easier after the 1st one lol. My Stingray was only 2 weeks old and still had the new boat smell when I installed them. It was either drill holes or get a different boat. The ride was that bad!!
I put Bennett Bolts on my Chaparral 226 SSI after owning it for 2 years and even though it rode good without them, they still made a big difference and I wish I would have installed them sooner.

LOL! Thankfully I"m not there. It's a good boat, I was just curious as to why I always seem to run trim down more than not to avoid porpoising.

I did the tabs on the Sylvan, but I've owned that since new and have replaced the seats, repaired the bow decking, replaced the livewell pump, replaced the gas lines, the ...

...I was am really used to that boat. I still love how for a novice it's pretty easy to work on. I love the Four Winns but like modern cars I think they expect a hobbit to work on it.

 

[Stinnett21]

It's true; except at the back where they have 'cut outs' that is supposed to help the hole shot.

It isn't a super bad issue, I was mainly just curious. I'd read in the owners manual about how you can trim up and get 'optimum fuel economy and speed' but I never get to what they show in the diagram. I'm guessing there is some 'in optimal conditions' subtext in there that isn't mentioned.

Those diagrams are usually large exaggerations. If you consider the trim gauge as 100% I can't get past around 40% before I reach the point of no benefit as Scott describes in post 5 above.