What is the best prop for my pontoon?

[glastron50gl]

What I'm trying to achieve is a speed of 20-25 mph with Rpm's in the high 3000 to low 4000. Or better stated the best fuel economy at 20 to 25 mph.
The pontoon is a 2005 27ft Harris Flotebote Crowne It is not a tritoon. The pontoons are 26" dia. With inside strikes.The pontoon sits very flat in the water and has very little bow rise while operating. The weight of the boat is 4200lbs rigged with motor. The motor 2005 140 hp 4stroke suzuki 300 hrs and just got its 300hrs tune/check up. 5400 to 6200 wot range. The pontoon has a 13-3/4" 17 pitch 4 blade solas amita alum. prop. rpms are 5400 with one person in the boat. 4800 loaded down. At 4800 loaded down 4 adults 6 kids plus gear I'm seeing 20 mph. The tubes have are clean. Original owner said it would go 34 mph with one person and 29-30 loaded down with two families. The boat can not be trimmed much before it cavitates. I had the motor height checked by marina and the top of cavation is equal with the bottom of transom pod.


Thanks Nutinbitin

 

[Silvertip]

Re: What is the best prop for my pontoon?

You are approaching this the wrong way. You first need to put an average load on the boat and make some wide open throttle runs while carefully noting the engine RPM (at wide open throttle). This sets the base line. You may already have the best prop but I doubt it. The wide open throttle rpm published by Suzuki means they want a prop on the engine that allows it to run within that rpm band -- "at wide open throttle" with what you consider an average load. A prop that does not allow that (either overrevs or cannot reach that range) means it's the wrong prop. If you attempt to achieve a five MPH speed increase by slowing the engine down then you are seriously lugging the motor and will be looking for a new one in a very short period of time. Fuel consumption will also increase because you need far more throttle opening to maintain that 25 MPH than if the engine is propped correctly. So once you have some WOT rpm readings with an average load, we will be able to narrow down the "proper" prop. It will provide the best fuel economy, the engine will be in the proper rpm band, and finally -- speed will be whatever that provides. It might be the same, slightly worse, or slightly better. But the fact remains, you do not select a prop by suggesting that you want to increase speed 5 MPH and lower engine rpm -- especially without any actual performance data on the existing setup.

 

[hwsiii]

Re: What is the best prop for my pontoon?

Nutin, Silvertip is 100% right as always, about how you find a baseline for picking a better prop. You haven't given us enough information to do an analysis of your problem at this time, but I know for sure the prop you are running right now is not the right pitch for your use on this boat. You should be getting more speed out of this setup than you are, although I don't know why at this point. A four stroke is not really the best choice for these hull forms, but that is what you have and that is what we will work with to find out where the problems are, I am posting a chart of three different motors to give you an idea of the differences between 2 strokes and 4 strokes.

Two Stroke versus Four Stroke

If you will fill this form out I will help you as much as I can.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing then do the same thing on the flywheel and turn the motor until the tape lines up with each other on the prop, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch, number of blades and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a digital tachometer and hour meter here: http://cgi.ebay.com/ebaymotors/Tacho...Q5fAccessories
RPM _________ Speed ______ GPS ______ No. of people ______ Gal. Gas ________
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.



H

 

[Silvertip]

Re: What is the best prop for my pontoon?

There is nothing inherently wrong with a four stroke on a pontoon. In fact I think it is a good choice. I have a Suzy on my pontoon and it is a great combination. However on my fishing boats I prefer a two stroke for the performance edge they provide.

 

[glastron50gl]

Re: What is the best prop for my pontoon?

Thanks. I will gather all the information I can and report back. The boat is still at the marina it has just completed a 300 hr tune up, new plugs,filters, timingchain checked compression check hrs at rpm range recorded, oil lube top and bottom. It should be in good working order. Nutinbitin

 

[steelespike]

Re: What is the best prop for my pontoon?

The rough rule of thumb is your motors gph(gallons per hour)at wot(wide open throttle)will equal ABOUT 10% of the horse power.In your case ABOUT 14 gph.The idea is to get the best speed with your setup with the motor operating within its rpm band. These guys will get you setup right.

 

[glastron50gl]

Re: For HWSII What is the best prop for my pontoon?

Re: For HWSII What is the best prop for my pontoon?

I'm going to go down the list as it was sent to me.
1. 2005 Harris FloteBote 270 Crowne
2. 27 ft 8ft 6" 3200 lbs draft 1'10" max cap 18 persons 2845 lbs total
3. 8 people and 20 gallons fuel.
4. cruising around lake. Big lake 10 miles to rope swing...5 miles to popular hang out.. 5 mile to favorite snokel spot. 15 mile to sand beach.. alot of cruising.
5. It is a pontoon the pontoon is 27 ft the toons are 27 ft long.
6. 140 hp 4 stroke suzuki engine Year is 2005 it has 270 hrs.
7. 140 hp Gear ratio is 2.38 :1
8. WOT is 5600 to 6200
9. Even
10. NA
11. No hydrafoil or trim tabs
12. Solas Amita 13-3/4" 15 pitch 4 blade aluminum prop (new)
13 5500 RPM 25mph GPS 2 people 15 gals gas
14. 490 ft above sea level
15. Just had commplete tune up plugs lube oil filter fuel filter seaform run through injectors.
16. The boat is new to me. The prop I stated above was added by the marina that tune it up. The they first put a Solas Amita 13-3/4" 17 pitch 4 blade aluminum prop on the boat after a weekend of use the boat was running poorly missing and surging. I just bought the boat out of state and when I went to test ride it it had a 14"18pitch 3 blade stainless prop. It did not have a breakaway hub and it had a wobble.. rough looking it needed replacment if I hit something solid it would ruin lower unit. So I had it replaced right away. It did not seem right that the boat performed close to the same with all three props and an untuned motor vs a tuned motor... So Im here.
17. New prop.
18. I would like to see more speed. Friends have 25 and 26 ft pontoons that see 34 to 35 mph I know I'm a little longer and 10 hp less ( they have Honda 150 and Yamaha 150 both 4 strokes. Also I ran all test up the lake and down the lake with double Bimini up with double bimini down. No change in speed or rpm's.
19. 3000rpms 11.5
3500rpms 14.3
4000rpms 16.9
4500rpms 19.6
5000rpms 22.2
5500rpms 25.0

 

[brumbyvet]

Re: What is the best prop for my pontoon?

I would like for you to explain why you think 4 stroke outboards are wrong for pontoons. I am very pleased with the performance of my 90 hp Merc EFI 4 stroke. I have yet to be outrun by another pontoon with less than 150 hp. This includes 2 strokes. On other online forums that are pontoon specific, 4 strokes offer many advantages over 2 strokes. By the way, I'm running a 13 1/8 x 16p SS Vengeance prop.

 

[glastron50gl]

For hwsiii. Pontoon info for prop

For hwsiii. Pontoon info for prop

Hwsiii, The post above has all the info you requested. Let me know if if need more. Thanks Nutinbitin

 

[hwsiii]

Re: What is the best prop for my pontoon?

Brumby, in my opinion 4 strokes are not the best options for pontoon boats because most of them do not have very good torque and HP curves in the lower to upper cruising RPM and the boats probably carry the lowest power to weight ratios of most planing boats, in fact Nutin's boat has 1 HP for each 34 pounds of weight when he is normally loaded. Most people buy pontoon boats to carry large amounts of gear and people and tow toys and people and thus they normally carry much heavier loads and most of the pontoon hull forms are not as efficient as most normal planing hulls. And they normally have less HP per pound of weight carried than almost all other planing hull forms.

NUTIN, in my opinion either you have excess water in a pontoon or your motor is not running correctly, because you are not getting the speed you should out of that setup. You should be getting a minimum of 30 MPH lightly loaded, even with the boat not setup right. Your Prop slip is very high, and it should not be that high using the Solas Amita props.

Prop Slip

Anti Ventilation Plate

I would also like a couple of pictures of the stern from the side of the boat taken from down low with the anti ventialtion plate parallel to the keel using a straight edge on the keel reaching to the anti ventilation plate to see if your motor is too far down on the transom, here is how to do it. And one picture down low from about 4? behind the motor as well so I can see the hull form at the stern.


H

 

[glastron50gl]

Re: What is the best prop for my pontoon?

Thank you for the review of my pontoon. I keep the boat at my dock and do not have a trailer to take it out. I will get the marina to take it out so I can take pictures. While its out how do you check the pontoons for water ? Each toon has 4 seperate compartments. Are there plugs in the toons somewhere? What you are telling me is what I was thinking. I spent alot of money to get the pontoon tuned up and it seems all I got was 4 spark plugs, oil change, Filter and the lower unit lube changed out. $750.00 does not go as far as it used to. Maybe the engine is fine and its the toons. Nutinbitin

 

[hwsiii]

Re: What is the best prop for my pontoon?

Nutin, it could be the motor and pontoon. But you have so much prop slip that some of it is probably coming from toons, maybe with excess water, and they should have inspection openings for each compartment. Since it stays in the water all the time I am inclined to believe that we also need to be looking at the bottom of the toons for aquatic growth as well, as that will add to the drag and prop slip. I am more inclined at this point to try and find what is causing so much prop slip, and then we can fine tune the motor, beause if we have exess water and/or aquatic growth then that will stop the motor from reaching maximum RPM. If the major problem we have at this time is motor related we still have to cut our prop slip by half of what it is right now.


H

 

[glastron50gl]

Re: What is the best prop for my pontoon?

hwsii, Had the tubes checked today they are clean and empty. The motor is running great, good compression, the plugs look perfect, clean fuel filters,throtle body is wide open and clean. I took pictures of motor while it was out and also one in the water to show how flat this barge sits.

Thanks Nutinbitin

 

[hwsiii]

Re: What is the best prop for my pontoon?

Nutin, the pictures you took were superb. From the pictures, I see that the anti ventilation plate looks like it is 2" lower than the bottom of the transom pod. And that will definitely lose RPM and slow the boat down. And from the other pictures it looks like you can move the motor up two more notches.


Anti Ventilation Plate Height

Before we do anything else I want to ponder on this for awhile.


H

 

[glastron50gl]

Re: What is the best prop for my pontoon?

Hwsii, Just a note I was thinking of dropping the motor one hole due to cavition. When the water gets rough 1-1/2 ft chop I cant trim the motor up at all. Plus if I do not put 75% of the weight in the back of boat. It will cavitate.
Thinking out loud with this long of a boat that sits fairly flat is a stern lifting prop the right way to go?

Thanks for your help. Nutinbitin

 

[glastron50gl]

Retread for hwsiii..

Retread for hwsiii..

Hey, You might need to read through the posts again and look at the pictures. I have high prop slip on my pontoon and it is causing poor proformance. Well its spring time again and time the clean the barge and play. While I was cleaning the tubes I noticed the transom pod that hold the motor had a low water line..... As the pontoon sits in the water only about 2-3 inches max of the transom pod is in the water. 12-13 inches of the tubes are in the water in back. This does not make sense... How can the motor get clean water to turn if the transom is not deep enough to smooth it out. Check the pictures.... On the other pontoons around I see 6 inches of the transom under water. thanks