Pontoon Boat & Deck Boat Forum

I finally got beat on our lake today.. smaller inland lake in michigan, but been having a problem trimming. All of my numbers say I'm on track with the right prop, but as soon as I trim it up to where my rpms are on point, it will start to porpoise. I can trim back down to compensate, but then I'm pushing more water and losing speed. I was right at 49 with 3 adults, 2 kids 30gal of fuel. I have been 51 with 4 adults, 2 kids and the bimini top open (no porpoise). Normal best is 2 adults 2 kids 53mph. I guess the issue is the porpoise, how do I keep it from doing it without trimming the nose in the water. Motor is a g1 300etec, with a 21p viper prop, mainly running between 5600-5800rpm. Boat is a Berkshire (southbay) 24'10" tip to tip Trifecta bp3. Thanks!

Don't get me wrong here as I do enjoy going fast but I'm at a loss as to why one wants to go over 50 MPH with an open playpen pontoon....

Talk to a prop expert as there is more to a prop than diameter and pitch... Rake is the angle of the blade from root
to blade tip and has a lot to do with lift. More cup may help with controlling lift; cup is the small curve or lip on the trailing
edge of the propeller blade. Another thought is to move some more weight forward, we used to stash heavy crap way forward on an over motored tri-hull we once had to help hold the bow down....

How does your engine handle going into a steep/short turn fast? Are you getting any ventilation? That's important on high performance tritoons. A lot of times, an engine mounted too high on the transom will ventilate easily.

Back when I had inboard ouboards on V hulled boats, whenever I raised the outdrive high it was going to porpoise. If I just barely tapped the trim down a little bit, it quit porpoising with little speed loss. It's sometimes just the nature of the beast.

If your nosecones are not out of the water when not porpoising, you may have an engine height problem or a prop problem. It can be like chasing your tail to get'em perfect. That's when you buy a prop from someone that'll let you swap a prop for another if it doesn't perform right.

Keep lifting the engine up a hole until the prop starts to break loose just as it start to porpoise. Usually I find boats that porpoise have the cav plate buried in the water and the engine needs to come up a hole or two. If the cav plate is already skimming the water at 3/4+ throttle trimmed out then its time to try different props, probably something with a LARGE diameter so you have plenty of bite on the water to allow you to lift the nose higher. Mine starts to porpoise at its fastest speed also, the only way I could climb over 40mph was with the nose bouncing but I'm starting at square one this year with all new tubes under my toon.

All great ideas here.. I've been debating on lowering the motor back down, it came from the dealer 1 hole down, which raised the motor. We had a demo boat very similar to ours to use for a few months while ours was being built and it was all the way down. I believe it handled better, just haven't moved it due to where it rides in the water seems to be right where it should and guessing that I'll lose some mph. The boat will ventilate if I throttle back, then get back into it, but trimming can usually fix that. Mainly only being an issue if it is falling off plane. Everything holds tight through acceleration, (sharp turns, hole shot, etc..) no problem. Then of course there is the never ending prop confusion. I may try to find some used, as I could probably use a slightly smaller pitch for heavier loads. We also have a prop shop here that I may try to pick his brain, maybe even have ours adjusted.

It's just sometimes difficult to setup some boat and engine combinations. And some dealers are better than others at setup.

There are relatively few really big 2 stroke motors that have been installed on tritoons, and which hole to install the motor and which prop to install is not a known commodity.

My Bennington 24' has the F150 Yamaha, of which there are hundreds of identical units on the water. My dealer nailed my setup as he's sold so many of these boats.

Your boat is just a different animal. Hang in there and you'll get it dialed in.

kweathers wrote:All great ideas here.. I've been debating on lowering the motor back down, it came from the dealer 1 hole down, which raised the motor. We had a demo boat very similar to ours to use for a few months while ours was being built and it was all the way down. I believe it handled better, just haven't moved it due to where it rides in the water seems to be right where it should and guessing that I'll lose some mph. The boat will ventilate if I throttle back, then get back into it, but trimming can usually fix that. Mainly only being an issue if it is falling off plane. Everything holds tight through acceleration, (sharp turns, hole shot, etc..) no problem. Then of course there is the never ending prop confusion. I may try to find some used, as I could probably use a slightly smaller pitch for heavier loads. We also have a prop shop here that I may try to pick his brain, maybe even have ours adjusted.

I am having prop issues also my 250 ho etech is running 49 mph at 6200 rpm's 14.75x 17 pitch prop that is four people 3/4 fuel load
with one person same speed ,,
is that the mackinaw bridge you are under?
we are on mullet lake I have taken my old pontoon out there great ride
so I am on my quest also to find the perfect prop

BIGFOOT63 wrote:

kweathers wrote:All great ideas here.. I've been debating on lowering the motor back down, it came from the dealer 1 hole down, which raised the motor. We had a demo boat very similar to ours to use for a few months while ours was being built and it was all the way down. I believe it handled better, just haven't moved it due to where it rides in the water seems to be right where it should and guessing that I'll lose some mph. The boat will ventilate if I throttle back, then get back into it, but trimming can usually fix that. Mainly only being an issue if it is falling off plane. Everything holds tight through acceleration, (sharp turns, hole shot, etc..) no problem. Then of course there is the never ending prop confusion. I may try to find some used, as I could probably use a slightly smaller pitch for heavier loads. We also have a prop shop here that I may try to pick his brain, maybe even have ours adjusted.

I am having prop issues also my 250 ho etech is running 49 mph at 6200 rpm's 14.75x 17 pitch prop that is four people 3/4 fuel load
with one person same speed ,,
is that the mackinaw bridge you are under?
we are on mullet lake I have taken my old pontoon out there great ride
so I am on my quest also to find the perfect prop

Are you sure about that prop size? That's the same as I'm running on a 115hp 18' tri-toon.

ron nh wrote:

BIGFOOT63 wrote:

kweathers wrote:All great ideas here.. I've been debating on lowering the motor back down, it came from the dealer 1 hole down, which raised the motor. We had a demo boat very similar to ours to use for a few months while ours was being built and it was all the way down. I believe it handled better, just haven't moved it due to where it rides in the water seems to be right where it should and guessing that I'll lose some mph. The boat will ventilate if I throttle back, then get back into it, but trimming can usually fix that. Mainly only being an issue if it is falling off plane. Everything holds tight through acceleration, (sharp turns, hole shot, etc..) no problem. Then of course there is the never ending prop confusion. I may try to find some used, as I could probably use a slightly smaller pitch for heavier loads. We also have a prop shop here that I may try to pick his brain, maybe even have ours adjusted.

I am having prop issues also my 250 ho etech is running 49 mph at 6200 rpm's 14.75x 17 pitch prop that is four people 3/4 fuel load
with one person same speed ,,
is that the mackinaw bridge you are under?
we are on mullet lake I have taken my old pontoon out there great ride
so I am on my quest also to find the perfect prop

Are you sure about that prop size? That's the same as I'm running on a 115hp 18' tri-toon.

that's what it says on it seems small to me

Bigfoot.. that prop does seem small to me also. Can't remember if it was the 17 or 19 but I was banging the Rev limiter. I also have the g1 where you prob. have the new g2 with a different peak. BTW that is the mighty Mac we are under.. last year end of July. We are planning same trip again, around the same time of year. We live around the traverse city area where most of boating happens.

kweathers wrote:Bigfoot.. that prop does seem small to me also. Can't remember if it was the 17 or 19 but I was banging the Rev limiter. I also have the g1 where you prob. have the new g2 with a different peak. BTW that is the mighty Mac we are under.. last year end of July. We are planning same trip again, around the same time of year. We live around the traverse city area where most of boating happens.

I just did a bunch of searches and the 17 pitch seems to be the norm I am thinking an 18 pitch just to drop rpm down a little but keep it around 5500 with a good load ,,where do you stay when you come this way in july?

Evinrude has a great site for test numbers. Seems like they're running 18 pitch on all the new 250ho's. This may not be the exact boat but is a good base reference.
http://www.evinrude.com/Content/Pdf/neu ... ontoon.pdf
We stayed at the Best Western river terrace in cheboygan, trying to maybe find a cabin in Indian river, mullet or burt lake

kweathers wrote:Evinrude has a great site for test numbers. Seems like they're running 18 pitch on all the new 250ho's. This may not be the exact boat but is a good base reference.
http://www.evinrude.com/Content/Pdf/neu ... ontoon.pdf
We stayed at the Best Western river terrace in cheboygan, trying to maybe find a cabin in Indian river, mullet or burt lake

there is a website that offer vacation rentals cant think of the name
here is a new Michigan face book pontoon page just started https://www.facebook.com/groups/1005974 ... 1/?fref=nf

Viper props are bow raisers. They have a lot of rake but the small diameter creates a lot of slip. I think you guys would benefit from Rebels. The bigger diameter seemed to work best for my first Manitou, with the stock 250 Etec. After the jackplate, tabs and spoilers, the RakerII worked best because the hull work helped force the bow down. They like bigger diameter props. See if you can run a Rebel, I think you'll both be very impressed!

Bryden24shp wrote:Viper props are bow raisers. They have a lot of rake but the small diameter creates a lot of slip. I think you guys would benefit from Rebels. The bigger diameter seemed to work best for my first Manitou, with the stock 250 Etec. After the jackplate, tabs and spoilers, the RakerII worked best because the hull work helped force the bow down. They like bigger diameter props. See if you can run a Rebel, I think you'll both be very impressed!

dealer has a 15 3/8 x 18 rebel coming I will try it this coming weekend!