pontoon prop?

tkdunn · Feb 16, 2012

I have a 20 ft pontoon with a 112 evinrude spl. It currently has a solas 13.5x15 3 blade aluminum prop. When running wide open the engine revs. I'm new to boating and don't know the correct terminology. Is this prop correct for my boat? I haven't taken the boat out since november but I'll try to answer whatever questions are needed. Thanks. :redface:

tkdunn · Feb 16, 2012

Re: pontoon prop?

I know in other posts people have asked about position of the prop in relation to the pontoons. So here is a picture of my motor when I was winterizing.

smokeonthewater · Feb 16, 2012

Re: pontoon prop?

Read This First!!

tkdunn · Feb 16, 2012

Re: pontoon prop?

Sorry I missed that thread. I'm new to iboats.

1. The problem is probably ventilation. From about half throttle to full throttle their is no speed increase it just raises the rpms. The engine revs especially if there is choppy water.

2. Solas 3 blade aluminum. I don't know the model but OD 4809 is on the prop.

3. 13.5 x 15

4. I looked online for the maximum rpms for my motor and it's 4500-5500. After hitting around 4000 rpms there is no speed increase. I can get to around 20 mph.

5. 1996 Evinrude 112 SPL

6. 2002 Playcraft Sunfish 20' long. I'm unsure of weight. I don't have an owner's manual so I'm unsure of where to get this information. I'm not close to where the boat is stored and can't check the weight ratings. I believe it was rated for 8 people.

smokeonthewater · Feb 16, 2012

Re: pontoon prop?

a few things come to mind...
1: motor height I suspect that as you get on plane your prop may be getting too close to the surface.... your antivent plate (flat fin over the prop should not get far from the water surface and I THINK on a toon it should stay just below the surface (other folks with more toon exp please correct if wrong) The fix would be a motor with a longer shaft.

2: spun hub in prop.... a paint marker can be used to make marks on the prop and prop nut so that it will be evident that the hub is slipping

Is this a new to you boat? If so have you asked the p/o about the history of the issue? If not a new boat, is this a new problem?

tkdunn · Feb 16, 2012

Re: pontoon prop?

I purchased this boat out of state last summer. I have no history for it. It's my first boat and I have no other experience with them. I don't recall the antivent plate being above the water. The worst i've seen the problem was during a storm in pretty choppy water running at WOT. I don't normally run under those conditions because it's just not necessary. Once the cold weather is over I'll try marking the prop and taking it out. I'm considering replacing the prop because of minor damage from knicking a fallen tree. Although the problem existed when the prop was in perfect shape. That's why I was wondering if I have the right prop for my boat.

steelespike · Feb 17, 2012

Re: pontoon prop?

I don't think you have a spun hub.A spun hub usually results in total loss of thrust
once enough throttle is applied even on calm water hub failure will progress with furthewr use.
I'm pretty sure you had ventilation due to the relatively rough water agravating the condition.
I think if you lower the motor one hole it should help.If your reasnably handy you can do it your self.
With a wooden block to set the skeg on raise the tongue of the trailer till the skeg rests lightly on the block
then carefull loosen the bolts that set the height leaving the adjustment bolts to secure the motor
lower the tongue till you drop the motor one hole. As long as your waiting the weather get the prop tuned up.
With the motor lowered get us the wot rpm and speed with the motor lowered.
I think your boat should reach at least 30 with the right setup.
Pontoons have high slip numbers yours are very high if your reaching 5500 at 20 mph.
A test with the motor lowered a hole will help.

tkdunn · Feb 17, 2012

Re: pontoon prop?

If I remember right my boat hits 20 at around 3500-4000 and maxes out at 22 at 5500. I just keep it in the 3500-4000 range because the extra 2 mph isn't worth the extra fuel. I think the motor is as low as it can go but I'm not sure about motor mounting.

I think I'd have to loosen the bolts with the red arrows. But looking at the area at the blue arrow, it doesn't look like there's any space for the motor to move down. Unless I'm completely confused and the adjustment is made at the green arrow. I was told that just limits how far back the motor can move. Please excuse my ignorance. :facepalm:

tkdunn · Feb 17, 2012

Re: pontoon prop?

In your opinion, am I running the correct prop? I know that this is not the motor that was originally on this boat. I don't know what if any difference it would make. I think it had a 50hp johnson. I wouldn't think it'd matter. The previous owner had this motor professionally installed and setup. That's the extent of what I know about this boat.

smokeonthewater · Feb 17, 2012

Re: pontoon prop?

I really think that the engine is too high... IE the wrong engine for the boat... we can HOPE that the hub is slipping.

When you get a chance to run it, check the hub first.... It didn't look to me like the engine could go any lower.... any chance that the transom bolts on in a way that it could be spaced down? I've never had a toon so I'm not sure how they're put together.

The green arrow limits how far the engine can be trimmed down.

Let's rule out the spun hub first and go from there, unless someone can post up how to measure shaft length for a toon.

tkdunn · Feb 17, 2012

Re: pontoon prop?

When i was winterizing I noticed the prop nut was extremely loose. Once the cotter pin was removed i was able to spin it off with one finger with only maybe 2 rotations. I had taken it off to grease the shaft. When I put it back I used a 2x4 to hold the prop while I tightened it down snug. What problems could I experience from the nut being loose? Other than possibly losing the prop.

Silvertip · Feb 17, 2012

Re: pontoon prop?

The motor is already sitting full down on the pod so it cannot be lowered further. It also appears the AV plate is well below the bottom of the pod so this is either a wrong prop or slipping hub. You will not lose a prop because the nut is loose since the cotter pin or locking mechanism prevents it from coming off. The splines are what drives the prop.

tkdunn · Feb 17, 2012

Re: pontoon prop?

As soon as I'm able I'll check for a slipping hub. I don't know what size prop would work best for my boat. Do you have any suggestions? I was considering purchasing another prop and keeping this one as a back up. It seems like 15 pitch is pretty common for pontoons though.

steelespike · Feb 18, 2012

Re: pontoon prop?

Really don't think its a hub issue but easy enough to check.
The 15 is a fairly common size though I've seen as small as 12"
It does appear there are no other holes to lower it.
Have you tried different trim setting.Pontoons usually won't allow much up trim.
I would suggest take the prop to a prop shop and explain your issue
probably not ventilation but high slip. They may be able to add some cup
or have other suggestions.

tkdunn · Feb 18, 2012

Re: pontoon prop?

It's possible that I haven't gained enough experience with trimming the motor and it isn't really an issue. I usually tried running it with the needle in the middle on the trim gauge. I haven't been able to locate a prop shop as of yet. I'd like to try to find a place local instead of shipping. I can order a new solas prop for around $100. Should I look for a pontoon specific prop?

steelespike · Feb 19, 2012

Re: pontoon prop?

Try a trim that seems fastest with the least venting problems.you may have to trim down
in rough conditions. The Solas Amita 4 blades have had good results.
Look for a large diameter with nice big blades.With your present results its difficult to
suggest a pitch but based on typical setups a 15" 4 blade is a good start. You might ask
about prop shops at the marina or the boaters at the launch ramp.My closest prop shop doesn't
mention props in its name and they have been at it for 40 years.Not only that but you can hardly see their sign from the road.

tkdunn · Feb 19, 2012

Re: pontoon prop?

Forgive my ignorance here but I thought the diameter had to be the same as the old prop? Or does it just have to be manufactured for Evinrude/Johnson with 13 splines? I'll call around and see what I can find out about a prop shop. I live within 30 miles of the largest lake in NC and about the same distance from other lakes. There is bound to be one relatively close.

steelespike · Feb 19, 2012

Re: pontoon prop?

As long as the prop is listed for your motor it should fit.If you look at the prop listings.
Generally as pitch goes up diameter goes down and you may note that 4 blades may be smaller than some 3 blades
of the same pitch.Thats due to the additional blade.

Silvertip · Feb 20, 2012

Re: pontoon prop?

What prop is "common" for pontoons depends on the engine HP and engine manufacturer. 40/50/60 Mercs for examle typically run a 14 x 9 on that size pontoon if the engine is a "Big Foot". Your engine probably has a 2:1 gear case so a 15P may be a bit too much pitch. We've not seen your RPM numbers and with ventilation being a problem you can't get accurate numbers. Trim gauges are simply a way of telling you how the engine is trimmed so you don't need to turn your head to see it. It is not a gauge that says "set the needle here for best performance". Trim all the way down and try. If that doesn't work try other settings. But by all means check for a spun hub first and don't buy props until you figure out what the problem is.

steelespike · Feb 20, 2012

Re: pontoon prop?

In my research for this thread I checked OMC motors of similar hp and same gear ratio similar sized pontoons,probably 10 setups
Props ranged from 12" to 15" with 15 slightly more common. performance ranged from about 29 to the high 30's.
We're dealing with a 112 OMC.My point at the time of my post was that prop size seemed to be all over the place
on boats of about the same weight and size.
If we can get this prop to get a grip with a little tweaking at the prop shop maybe we can tell better what prop is needed if any.

pontoon prop?

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