Best way to avoid porpoising

[viperdrum]

I have had an 08 225 about a year. Great boat and nice ride.

Often on the river, when I am the only one on board it will begin porpoising for no apparent reason. I play with pulling the prop up and down and it sometimes helps but I guess i don't understand why it seems to happen in generally calm water.

Why is this and what do you all do it make it better? Thanks

 

[jekyl]

The fact that you are the only one aboard probably means the boat is probably lightly loaded. Then In calmer seas you generally run with the motors trimmed out and thus the bow high.
Calm seas are not necessarily flat, they will still have underlying swell that is not noticeable like chop on the surface. This is sometimes from a passing vessel or residual weather or current.
My solution would be to trim the motors in more and make sure you have more weight up towards the bow.
Manufacturers build the boats with a designated normal load. ie 4 people , half a tank of gas, full water and gear and place fuel tanks , water tanks accordingly. When you run a larger vessel outside those norms then some compensation needs to be made.

 

[seasick]

A small change in trim angle can make a big difference. When you have additional passengers, the weight lowers the bow. You need to lower the bow when the purposing starts. Note that the correct trim angle is only good for a narrow speed range. As you speed up and slow down, you need to retrim as necessary.

 

[gradyfish22]

Adjust yout trim angle and shift gear in the boat, what is happening is your boat is getting too much lift and trim angle and not enough boat is sitting in the water. In rougher seas the waves help to counter act this, even at the same trim angle and speed and such, since the wave action will affect the boats natural tendancy to porpoise. The prop is not your problem, but the light weight of the boat and the location of weight in your boat. Being that it is a 225 and you are placing the engine on a bracket, your making the boat seem even longer and basically having even less water below you then you should on a boat that is actually that size at the water line. You can use tabs to adjust your trim angle, as well as engine height, and then lastly shifting weight in the boat. You may have to experiment to see what works in the end, typically though you have too much weight forward for some reason ro are very light aft for some reason. If your tabbing down that can do it too, yes tabbing down is nice in flat calm but do it too much and good luck. Also tabbing up too much can cause the boat to want to follow an occilating as well . See what happens with no tab and just by using the engine trim to adjust the running angle, using no tab is best when possible since they cause drag anyways and reduce your efficiency.

 

[Tashmoo]

Viperdrum,

What going on have not seen you on line for a while. Hope you well and are happy with your new Tournament.
I have a few questions for you and then a comment. First how much current is in the river? Does the boat porpoise with, against or in either direction with the flow of the river? Next how fast are you going when this happens? Did you do anything to the engine to make it go faster than factory?
If memory serves me you have a bracket which moves you center of gravity on the boat back, this coupled with the current which effectively makes your speed over the water faster could be the issue. So my guess is that you have the problem going fast into the current.

If I had this I would be all over my dealer as a new GW should not behave like this. Either way call GW and put the problem on them to resolve if your dealer can’t or won’t figure it out.

 

[mjtyszki]

Do you have a whale tail (cavitation plate) on the motor? If you do you can also try to adjust it some. The trim options are the first source that I would check, I have seen many people have the motor trim and tabs work against each other, so play with both...

If the trim doesnt work, it may be a long shot but I would try to work with the plate a little. Afterall, it is a lot cheaper than paying someone to figure out what is going on...

 

[Bay Drifter]

Viper, something does not sound right. I have the exact same boat setup as you. The only time I have experienced porpoising is when I get too greedy with the engine trimmed out to far going for max speed and mpg at a given rpm. I find the boat to be well set up when I am solo. No trim tab needed and can usually run the trim out a quarter pass mid on the trim gauge. It loves to run in this mode.

Is the boat butt heavy for some reason. When mine is at rest the waterline is middle of the scuppers. This is in mid Chesapeake bay where the salt content is not huge. I hope the bracket is not full of water or something wierd like that. Hope this helps. Sorry for the late post have not been here for a while.

 

[capt chris]

Viperdrum,
I have your identical '08 boat and run it on the Ohio River and Lake Cumberland. All fresh water. I have always been able to stop the porpoising by trimming the motor down and bringing the bow down. I really only use my tabs to balance out uneven loads or when the wind has really kicked up the swells. It does seem like the porpoising starts for no good reason, but when I look around I usually find it to be an errant wake that didn't seem to look big enough to cause it. I almost always have to trim down to stop it and then trim back up once it stops.