Top Speed with a Tritoon

[brotherkicksave]

Hello,

I own a 23ft Crest Tritoon powered by a 150 Mercury Optimax. 15 x 15 triple SS prop.

The Tritoon holds 47 gallons of fuel, I usually keep it at half a tank for weight purposes.

I have a moderate amount of gear that stays on the boat and I usually carry 6 passengers.

With WOT, I saw 4800 rpm today and roughly 28 mph (GPS).

Does this seem slow to anyone else??

Shouldn't I be seeing 34 or 35. The Mercury website showed a test of 23 Crest Tritoon with a 150 OptiMax (w/ 47 gallons) and they saw 34mph with the same prop.

Is it possible that I am not getting WOT???? How do I determine this?

Steve

 

[MH Hawker]

Re: Top Speed with a Tritoon

What it the max RPM that the motor is rated for.

 

[muskiemike12]

Re: Top Speed with a Tritoon

Looks like its rated for 5250 - 5750. Your motor is lugging. Can you raise the motor on the pod?

 

[The Rooster]

Re: Top Speed with a Tritoon

Looks like its rated for 5250 - 5750. Your motor is lugging. Can you raise the motor on the pod?

+1^^^ Steve you are nearly 1000 rpms lower than max output for your motor. Good luck !!!

 

[brotherkicksave]

Re: Top Speed with a Tritoon

Yes...The mounting bracket is resting on the pod. The motor is mounted as low as it can be currently. Should I check that I am getting WOT?

 

[MH Hawker]

Re: Top Speed with a Tritoon

Isnt 4800 your present WOT. And it looks like the rpm range is 5250 - 5750 then yes its over propped. so lowering the pitch by 2 should bring it up 400 to 600 and put it in the right range. So going from a 15 to a 13 should do it.

 

[brotherkicksave]

Re: Top Speed with a Tritoon

That's my point. The same boat with the same engine, the same fuel load, and the same prop is doing mid thirties mph. I wonder if I am getting WOT???

 

[crb478]

Re: Top Speed with a Tritoon

Something is wrong, you should be going faster. Make sure your toons do not have any water in them, an they are clean. Then you might want to play around with motor height or a new prop. A 150 should be able to turn a 15 pitch with a full tank of gas

 

[WaterDR]

Re: Top Speed with a Tritoon

I have a 115 and have a 13 by 15 and run 30. My toon is over 25 feet.

 

[muskiemike12]

Re: Top Speed with a Tritoon

I noticed on the test that the motor was mounted on the 4th hole, not sure what that means.

 

[brotherkicksave]

Re: Top Speed with a Tritoon

I noticed on the test that the motor was mounted on the 4th hole, not sure what that means.

I'm going to a) check the toons for water. b) check the throttle body for WOT c) Move the motor from "1st" mount holes to "4th" holes.

Thanks, I will keep you posted.

Steve

 

[brotherkicksave]

Re: Top Speed with a Tritoon

Ok... There is NO water in any of my toons. And I am seeing 4900 RPM and 33 MPH at WOT. I know if I drop from a 15 pitch to 13 pitch I will gain the RPM's I need for the engine to perform "at peak". I wonder if I'll gain top speed? Anyone?

 

[WaterDR]

Re: Top Speed with a Tritoon

if you are not in the correct rpm range now, then yes, if you change prop such that the rpms increase, you will gain top end.

You should run the prop such that at light load, you max out the top end of your rpm range w/o hitting the rev limiter.

In my case, I hit 6,000 rpms pretty much regardless of how much weight I add. My trim matters not either unless I over trim it too high and start to loose water.

in other words, with the motor trimmed down I hit 6,000. With the motor trimmed up, I hit 6,000 but I gain a few mph.

 

[brotherkicksave]

Re: Top Speed with a Tritoon

Yeah...I still dont understand why I am not seeing more RPM. The Mercury website tested my very same boat (boat, engine, prop, fuel level) in January and saw 5300 RPM. I don't get it.

 

[craigmack]

Re: Top Speed with a Tritoon

OK, just so I understand correctly... the rpm and speed is with 6 people? If so, that sounds a bit low but in the ball park considering most prop setups done by dealers and tests are done with two adults (avg adult being 180 lbs). If six is your most common number of adults then yes you'll need to reprop to a lower pitch. I propped mine with two adults and a teenager since that's my most common load and I'm getting 5500 rpm @ 40 (speedo, most likely 37/38 gps). When I had six adults and a child I dropped to around 5000 rpm @ 34 (speedo) IIRC. So our ratios are not that far off. Now, if that speed if with just you then something is really wrong.

What make/model of prop?

Not to hijack this thread but...
WaterDR, I don't understand how you can add significant weight and not affect rpm/speed.

 

[MH Hawker]

Re: Top Speed with a Tritoon

your not propped right

 

[Rancherlee]

Re: Top Speed with a Tritoon

Personally I'd figure out how high you can go with the motor, then drop ONE pitch if the same prop is avalible in a 14" pitch. And yes, 6 people can cost you 5mph+ over "test results" I loose 6mph on my tritoon with 6 people vs just me but than again I only have a 70hp engine on the back.

 

[brotherkicksave]

Re: Top Speed with a Tritoon

I saw 33GPS/mph, 4900 RPM at WOT with just me and 23 gallons of fuel. If I take the trim up to just under cavitation, I will see 5100RPM with no change in speed.

@MH, Same boat (Crest Tritoon), Same Engine (Mercury 150 Opti), Same Prop (Mirage Plus SS 15 3/4 x 15P) sees 5300RPM. THE ONLY thing that is different on my boat from the test boat is the engine mounting location. The test shows "Mounting position #4", whereas my boat is on mounting position #1 or all the way down on the transom. When the boat is out of the water the cavitation plate is in perfect alignment (1 inch lower) with the bottom of the center toon.

 

[craigmack]

Re: Top Speed with a Tritoon

Well, given the data supplied an online prop slip calculator shows you having 11% slip (given a 1.87 gear ratio). You could try 1 hole higher at a time and see how that effects your numbers. Granted that's a lot of work and $$ if you have to pay marina labor rates.

Now, given the data (34 @ 5300) for the test boat you referred to it calcs to 15% slip. If that is indeed that case then you're setup is grabbing better.

For comparison, if I see 38 gps (I'm testing this weekend) mine calcs to 7% slip.