Problem?

[MerkFalc]

New to pontoons so I'm not sure if I problem or not. Ran the pontoon yesterday for about 6 hours on smooth water and it would run about 35 at 5000rpms, but every I gave it more throttle it would only raise rpms and no speed. The trim on the was almost all the way down the whole time, and any time I gave it a little more rpms would just shoot up. Seemed like the bow wasn't lifting at all. I had three adults, a six year old, and a couple of ice chests on there. Is this normal? It's a 25' tritoon voyager w/ a 225 optimax on it. On the sea trial we had it at 43 in rough seas with 5300 rpms. Other than that, the boat ran great and had an awesome time fishing! Only one little striper, but as I told my brother (who canceled coming down), "A bad day fishing is better than a good day in Amarillo!"

[tuned]

Welcome to ya mate!
There a fair few guys that can likely help on something like this. Sometimes we don't always agree tho
That being said, there may one of several things going on (or a combination of things). Start by experimenting with one thing at a time. You were touching on the first one when you mentioned your load.
1. Try moving your load sternward. Were your adults and coolers all at the bow? This is prolly not too likely the issue as you have a large boat with lots of flotation as well as plenty of horsepower to hold the bow up as you trim out. Experiment with this anyway to learn how your boat responds to these changes.
2. Motor height. This is inter-related with how your load is distributed. If you bought the boat recently at a dealer, talk to them about this and maybe drop it an inch. It sounds to me as if you are 'blowing out' just a bit. This can also be dealt with in a different way, which brings us to a third parameter:
3. Propping. I would guess that this is what you need to look at. There are a million props out there with just as many different thrust and lift characteristics. Some of the guys with heavier boats like four blade props (I do) which typically give more reliable thrust and less blowout, although at a slight loss of top end speed. If you modify the name of this thread to include the word 'prop', you will likely catch the eye of several guys that have a lot more knowledge than myself in this area. Don't forget to mention the prop that you are currently running.

You mentioned sea-state and that certainly will affect how you run. Most boats like a little chop and actually run faster in it.
Good luck to you, and don't forget the

[MerkFalc]

Thanks for the quick reply! Most of the load was in the mid part of the boat so I don't think the weight distribution was off. The motor is already buried into the water, and could probably come up a whole judging by where the motor looked at speed. It was throwing a bunch of water and I couldn't see the top part of the flat outboard part. The prop is a 17p stainless steel vengence. It's a used boat and I know the PO had a different prop on it before, but the boat shop put the wrong prop on it before sending it back.

[tuned]

Hmmm. Sounds like you are maybe on the right track with the prop.
I don't know about raising the motor mount as you are already blowing out a bit. Typically, raising would make that worse.
Is the Vengance a 3 blade? Perhaps try a four blade if you can find a prop guy that will let you experiment? Enertia or Powertech OFS come to mind. The fourth blade will give you more bite and both those props are known for 'stern lift' which may get your caviation plate to ride higher in the water flow. You may lose a hair of top end, but with a nice gain in overall performance, which is what I personally prefer.

[MerkFalc]

Since you mentioned the prop I started doing some research and it looks like the vengence isn't a great pontoon prop. I guess there isn't enough cup on them and it's meant for more of a ski boat. I don't know of any prop shops around the Waco area, I'll give the local mercury shop a call tomorrow and see if they have any suggestions. Thanks for getting me on what I think is the right path!

[Brashanic]

I just had my toon out for the first time loaded with people. Trim, rpm,mph as well as all handling characteristics were vastly different than I light load. So much so that I kept thinking something was wrong with the boat.

[rsmith]

Our dealer initially put a Vengence on our toon, we switched to an enteria prop and have been much happier with it's performance. Change pitch with the enertia as well and ended up with better overall performance. I think the Vengence is better suited to bass boats than toons.

[MerkFalc]

The boat definitely handled differently, but it felt like the the prop was blowing out around 5000rpms.

You mentioned swapping to the enertia prop, what pitch did you end up with? I'm not sure if I need to go up or down or stay with the prop change. I know something with more cupping and a little larger in diameter.

[JohnO]

If I read correctly you said the trim was all the way DOWN. This means you are forcing the bow DOWN into the water rather than letting the motor lift it up.

Try it again with the trim neutral or up and you should see a huge increase in speed (several MPH).

With the bow trimmed down you are trying to plow through the water rather than plane over it. Running as you were, you were operating entirely as a displacement hull. Generally the speed of a displacement hull has a limit after which no reasonable amount of additional power will increase the speed. When you trim up you'll get the bow out of the water and shift into more of a planning hull mode. Much greater speed available there

Before messing with anything else trim the motor up and see what happens

[Bryden24shp]

The motor is already buried into the water, and could probably come up a whole judging by where the motor looked at speed.

Adjusting the motor up is simple, free and the first place to start. Before thinking of propping. Get the cavitation plate riding just on the waters surface. Then start propping.
Have fun with it, I love this stuff!
Bryan

[Bamaman]

We assume your triton has lifting strakes???? The Merc Enertia is the standard of the industry for pontoon/triton boats, and it's available in every pitch to allow most boats to get the most performance available. The whole trick about these boats is to trim the nosecone up out of the water to get the maximum speed and efficiency. Leave the nose down, and you've just got a displacement hull--and the boat will just hit a speed wall.

[MerkFalc]

I'll try lifting up the motor and see how the boat responds before I mess with the prop.

As far as the trim, trimming it up resulted in a ton of slipping with high rpms, slower speeds, and no real bow lift.

Appreciating the advice, keep it coming!

[JohnO]

Sounds like you have other issues going on. It seems odd that you are getting blow out with any trim up at all. Sounds like the motor is mounted too high to me. You don't have enough water on the prop to let it bite.

When the boat is at rest and the motor trimmed neutral the anti-cavitation plate should be even, or just above the bottom of the motor pod (center tube). (There is usually a smaller plate on top of the large plate which is immediately above the prop. This smaller plate should be a couple inches above the bottom of the tube) Of course, as with all things, this can be prop dependant.

I run a Yamaha 17P reliance Stainless prop on my 175 HP motor and I get 41.1MPH in perfect conditions and a light load. I have no blowout when trimmed all the way up.

It could be that the previous prop worked well at the motor height you are at now but you're too high for the new prop.

[Cycleman07]

I had this happen on my new South Bay a couple of times last summer. Get a big Crescent wrench and make sure the prop nut is tightened down. Mine backed off ever so slightly last year even with the locking clip on. I could only tighten it about a quarter turn when it did it but it made a world of difference.

[ToonGuy]

A pic of the stern would be helpfull.