New toon owner - boat / motor speed in turn question

[Gravelyctry]

Hello all, my wife and I just bought a 25' Voyager tritoon (2000 model). We took it out yesterday for the first time, and a few things seemed odd about it. It has a 175hp mercury motor.

First, I had to have the motor trimmed completely down or the motor speed would increase and the boat would slow down. I'm guessing the prop isn't getting enough water. Should I try to lower the motor down or adjust something else? My tach gauge doesn't work, but as long as I kept the trim all the way down it didn't do this.

Secondly, when going into a turn, the motor would rev up and I would lose speed. I assumed this was because one of the logs was pushing water away from the prop, but it was a little frustrating. I did a search, and it sounds like exactly the opposite happens to others, that is, in turns the motor bogs down rather than revs up. What causes this, and what can I do to fix it?

Thanks for any and all feedback. My only other boat is a flat bottom with a mud motor on it, so this thing is a whole new animal for me. Also, we were pulling a tube with 2 kids on it most of the day, but their combined weight was probably only 150 pounds.

Thanks,
Neil

[MPosey519]

When it does this, can you slow the throttle and get it to bite again, or do you have to take it all the way back to idle? If so, you might be having hub slip on the propeller. I had that issue and replacing the hub/prop fixed.

[Bamaman]

Chances are that you're getting some ventilation from your propeller. That's usually a product of having the motor trimmed up too much, and you need to lower the prop.

On my old 2 toon boat, every time passengers loaded down the nose of the boat, my motor would lift and I would also get ventilation. My motor was as far down on the transom as possible. I just asked passengers to move to the back of the boat. In reality, I should have made mods to my transom plate to bring the motor down--or install a jack plate. Sometimes a propeller change (less pitch) will keep water on the propeller longer, and they won't ventilate.

[Gravelyctry]

I pretty much h ave to go all the way back down to idle before it seems to recover. Does that mean the prop. Is slipping on the hub? Thanks, Neil

[HandymanHerb]

Sounds like you need a new hub for your prop, that will cost you some where around 40 bucks

[MH Hawker]

Run a prop test first, make some straight line marks on all 3 parts of the prop, then take it for a ride , then pull it and look at the marks, if their not lined up as you made them then you know for sure, it has 3 parts a splined shaft that goes on the prop shaft its self , a rubber hub and the prop its self.

[Gravelyctry]

OK - I'll do the prop test and draw the lines on it.

Next question - I took the GPS out on it last night (the speedometer and tach do not work) and it would only get to 29.5 mph going down river (on the Mississippi). It had only a half tank of gas, 3 kids younger than 10, 3 skinny girls, and myself. So not too much of a load.

I have no references other than some internet posts that seem like others are getting higher speeds with that size of a tritoon and a 175hp motor. Does the fact that I'm only going 29 suggest that something is wrong? The motor seems like it runs fine.

Is my next step to get the tach working to do any diagnosis, or do you guys think the 29 doesn't necessarily signal an issue?

Thanks,

Neil

[willy13]

You will need to get the tach working to make sure you have the optimum prop. Otherwise you will never know for sure if you could get some more speed out of the engine.

[Gravelyctry]

I haven't had a chance to run the prop test yet, but I called a local dealer to see if he has the replacement hubs in stock.

He wanted to know what it was doing, and according to him, it can't be the hub since the boat "recovers" after idling back down. He said once a hub is spun, it's done, and doesn't work anymore.

Is he right, or could the issue still be the hub?

Thanks,

Neil

[HandymanHerb]

I think he's full of it, they do it in rubber so you can still limp home if you spin it, order it from i-boats.com or at least check prices

[rancherlee]

I would say 29mph is in the ball park for a 25' triple toon with a 175hp and the load you had, kinda at home plate though, not the outfield Now if it a straked triple then id say your a touch slow and should be in the 33-35mph range with that load.

[JohnO]

What size prop? If you're propped wrong (too small of pitch) you'll not get the speed you want
What RPM are you turning at WOT?

The loss of speed in the turns is pretty common from what I understand. I had a 15 x 15 1/2" (pitch x dia) aluminum prop on my boat and had the exact same thing happening. Although when I trimmed down it would regrab. I then went to a 17 x 13 1/4" Stainless and most of that problem went away. I still have some of it but no where near what it was.

I get 41.1 MPH (top end, clean hull, light load) and 39.5 MPH or so under normal load. So you seem to be running a little slow (if you are straked and underskinned).

[Darin]

I think he's full of it, they do it in rubber so you can still limp home if you spin it, order it from i-boats.com or at least check prices

I disagree. I spun a hub on a 24' cobalt stern and it wouldnt move. I had to be towed in. They make them in rubber so they will flex a little and absorb some shock in case you hit something. You may be able to limp along for a while but it will continue to slip a little more everytime you throttle it up.

[Gravelyctry]

Ok, here's what I've found so far. I made a line and it looks to me like it spun, so I'm going to get that fixed.

Here's what I'm thinking now. I'm just going to get a new prop, since this one is dinged up pretty good and well used. So I've been looking at the mercury prop selector, and a few others, and I'm thinking of getting the aluminum Black Max extra cup 16x14.

I pulled it off the water today so I could work on it this week, and found that it has a 14.75x21 prop on it. That seems to be way off of what it should be.

I'm not going to go crazy trying to get every last bit of speed out of it (its a pontoon), but wanted some feedback on the prop I'm considering. Stainless vs aluminum. I'm going to be in the Mississippi River 99% of the time, so the water is always dirty. Does that mean I'd be better just getting the stainless prop. I considering the Al because its cheaper.

Second, I'm looking for some confirmation that the prop that was on it was way wrong. Again, it's a 25' voyager tritoon, with a 175EFI Mercury 2 stroke outboard.

Thanks for the help so far! Neil

[curtiscapk]

it seems way overpropped before!!! I would do aluminum on the ol MISS! if you hit something the prop will go not the lower unit...

Welcome aboard!