Repowering 20' Weeres Pontoon... Need Advice

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

Thanks guys! I am hoping to have a tachometer installed this week. I will be very careful when checking the new prop. Hopefully the original recommendations will be on the money. Since my WOT range is 4,500 to 5,500...I will need to be around 5,200 to 5,700 with a minimum load at WOT. With a heavy load, would the WOT RPM drop enough to keep it below 5,500? ...I can always throttle back when loaded lightly. Thanks again!

 

[Silvertip]

Re: Repowering 20' Weeres Pontoon... Need Advice

Wrong philosphy. You do not prop for minimum load unless -- and only unless -- that is the way the boat will be operated most of the time. If you prop for minimum load and then expect it to perform decently when in fact the boat is loaded more heavily you will indeed be lugging the engine. Weight requires power. The only option you have to compensate in that regard is throttle and prop. You cannot throttle up if the prop is wrong (too much pitch and the engine is lugging). That creates horrible fuel economy and builds carbon deposits. You can always throttle back if the engine tends to over rev. If this were my boat I would load it up the way you will operate it 75 - 90% of time. Then test and select a prop that puts the rpm at 5500 - 5700. 5700 is not of any consequence as far as overreving is concerned. Yes you will need to throttle back when you are alone or very lightlly loaded. Remember, loading is the issue.

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

Sorry...poor choice of words on my part! When I said minimal load...I was actually thinking of the way we would normally be operating (two adults and our fishing gear...which would be lightly loaded). We seldom load the boat with multiple passengers. Probably only 2 o3 three times a year would we have more than 5-6 on board. Guessing that 85% of the time, just the two of us and fishing gear.

 

[Silvertip]

Re: Repowering 20' Weeres Pontoon... Need Advice

Gotcha!

 

[Bamaman1]

Re: Repowering 20' Weeres Pontoon... Need Advice

Good luck with the 90 2 stroke. It's the right size for your pontoon. It should also accelerate like a bass boat--up until it "hits the wall."

I like the larger motors, as you don't have to run them at full throttle @ cruise speed. I'm running a 115 hp Yammie 2 stroke, and I'm planed off @ 2500 rpm's--running quietly and efficiently.

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

Thanks Bamaman1. The dealer is having to do some carb work to the engine. I hope to have it back on Thursday. Yes...I will like the idea of running at partial throttle and actually moving! With that in mind...I am hoping the fuel burn will be close to the 50 when it was running at 90-95%.

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

OK. Tach installed. Withe the 13x19 aluminum prop, I ran 31 MPH at 4,100 RPM. WAY too low. I installed the new Solas New Saturn SS prop, 13 3/4 x 13. My best RPM is only 5,100 at 27 MPH. The prop use by Yamaha for their Performance tests on the pontoons was a 13 5/8 x 13. Solas does not have a 13 5/8 diameter prop. What changes would I expect going to a smaller diamter? I really want to be closer to 5,500 RPM at WOT.

EDIT: I am not able to find a SS prop that is either smaller diamter or pitch that is appropriate. Any suggestions?

EDIT: I found a Stiltto D 811313 prop, 13-1/4 x 13. Just unsure about the effect of the change in diameter. This prop requires a hub kit...don't know what that is but I will read some more!

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

OK. Tach installed. Withe the 13x19 aluminum prop, I ran 31 MPH at 4,100 RPM. WAY too low. I installed the new Solas New Saturn SS prop, 13 3/4 x 13. My best RPM is only 5,100 at 27 MPH. The prop use by Yamaha for their Performance tests on the pontoons was a 13 5/8 x 13. Solas does not have a 13 5/8 diameter prop. What changes would I expect going to a smaller diamter? I really want to be closer to 5,500 RPM at WOT.

EDIT: I am not able to find a SS prop that is either smaller diamter or pitch that is appropriate. Any suggestions?

EDIT: I found a Stiltto D 811313 prop, 13-1/4 x 13. Just unsure about the effect of the change in diameter. This prop requires a hub kit...don't know what that is but I will read some more!

BUMP... I'm still in need of help!

 

[Jeep Man]

Re: Repowering 20' Weeres Pontoon... Need Advice

Why are you looking for stainless steel? Usually they are on more higher powered boats. Most common for pontoons is aluminum, and they are a lot less in price compared to SS.

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

Why are you looking for stainless steel? Usually they are on more higher powered boats. Most common for pontoons is aluminum, and they are a lot less in price compared to SS.

Ray,
We do a lot of shallow water fishing. Around the Bay and Gulf we frequently fish shallow weret there are lots of oyster shells, etc. They will destroy an aluminum prop quickly. Even dragging the prop throught the sand will wear it. When fishing in the rivers, we frequenly operate where there are obstructions that could easily damage an aluminum prop. You are right...the cost would be a lot less! Thanks for comment!

 

[Silvertip]

Re: Repowering 20' Weeres Pontoon... Need Advice

5/8 inch in diameter means nothing. Diameter is part of the prop design and is just one of many factors including rake, pitch, blade shape, hub, vented or not, cupped or not, and the list goes on. ASre you certain the PULSE setting on the tach is set correctly? I believe it should be set to 6 on that engine. When purchasing a prop here are the basic criterao:

1) It must be designed for your engine (that means there are several gear case sizes and gear ratios in any manufacturers engine line-up) Your engine falls in the mid-range of the Yamaha series and props MUST be in the 13 - 14 inch diameter range. Larger props won't work because it may hit something. Smaller props would simply blow out/

2) Select a prop designed for the application (V-hull, pontoon, work boat, barge, go fast boat, etc)
3) Select the pitch that puts the engine at or near the top fo the rpm band for the engine with a typical load.
4) Do not worry about diameter. Even within the same prop manufacturers line, a 13P prop will have a slightly larger diameter than a 19P. Generally as pitch goes down, diameter goes up and as mentioned, it is part of the design. Never worry about this difference when looking at props from different manufacturers. A 13P prop from manufacturer "A" may indeed have a different diameter than a 13P prop from manufacturer "B".

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

5/8 inch in diameter means nothing. Diameter is part of the prop design and is just one of many factors including rake, pitch, blade shape, hub, vented or not, cupped or not, and the list goes on. ASre you certain the PULSE setting on the tach is set correctly? I believe it should be set to 6 on that engine. When purchasing a prop here are the basic criterao:

1) It must be designed for your engine (that means there are several gear case sizes and gear ratios in any manufacturers engine line-up) Your engine falls in the mid-range of the Yamaha series and props MUST be in the 13 - 14 inch diameter range. Larger props won't work because it may hit something. Smaller props would simply blow out/

2) Select a prop designed for the application (V-hull, pontoon, work boat, barge, go fast boat, etc)
3) Select the pitch that puts the engine at or near the top fo the rpm band for the engine with a typical load.
4) Do not worry about diameter. Even within the same prop manufacturers line, a 13P prop will have a slightly larger diameter than a 19P. Generally as pitch goes down, diameter goes up and as mentioned, it is part of the design. Never worry about this difference when looking at props from different manufacturers. A 13P prop from manufacturer "A" may indeed have a different diameter than a 13P prop from manufacturer "B".

Silvertip,
Thanks again for the reply. I am using a Tiny Tach that is set to "one spark per revolution." Based upon the idle speed of 750-800 RPM...I believe the tach is correct. Part of my problem is that I can not find a prop in my diameter range that has a smaller pitch than 13 (and will still fit the 15 spline Yamaha 90). The Stiletto I mentioned earlier is 13.25x13. So the only change there would be 1/2" smaller and possibly a slightly different design. And based upon your reply, the 1/2" difference wouldn't make any difference in RPM. So...at this point I am unsure what to do. Purchasing another prop that is going to yeild the same results doesn't make any sense. So, what should I do, based upon what SS props are available? I would really like to be operating at the upper end of 5,500. Thanks!

 

[Bamaman1]

Re: Repowering 20' Weeres Pontoon... Need Advice

I originally was running a 19' inboard outboard boat with an aluminum prop. We had to visit our prop shop twice yearly to get the prop reconditioned. (Fortunately, the prop shop owner is a cousin.)

When I switched to a stainless steel prop on a new inboard outboard boat, we got 12 years' usage with just minor scratches. Stainless props are much more durable, faster, and get better mpg (efficient.)

I bought my pontoon boat in 1985, and I have never had my prop to a prop shop. I just don't take a 24' boat into shallow waters, as I don't fish from it. We are a very deep water river/lake.

You can buy 3 aluminum props for the price of a single stainless prop. But if you're going to be fishing in shallow water, crunching the sand/seashells bottom or fishing in coral, you'd be better served going stainless. If you're running a high horsepower pontoon/tritoon boat, you might also be better served with a stainless prop AND a hydraulic jack plate to get the optimum engine height to match the boat's load.

 

[Silvertip]

Re: Repowering 20' Weeres Pontoon... Need Advice

You are rapidly learning why prop selection is such a crap shoot. your hunt for props apparently ignored right here on I-Boats. They go down to 9 pitch. Here is the link to the Yamaha prop listing.

http://boatpropellers.iboats.com/Yamaha-Outboard-Propellers/?engine_id=403&*******=640858957

Another variable is comparing props (say 13P) from two different manufacturers. Those two props will very likely perform differently even though the pitch is the same. Why? Because the manufacture may have tweaked the design for hole shot of mid range performance while the other manufacturer tweaked his design for pure top end. And then you have yet another variable where you try to compare two 13P props from the same manufacturer but the props are two different models. Again there will be a performance difference. Want more confusion? Switch from aluminum to stainless (same manufacturer - different models) and conversely, switch from Mfgr "A" aluminum to Mfgr "B" stainless. See where this goes?

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

Silvertip,
I had been looking on iBoats as well...however, the page your link took me to was a page I had not seen! Apparantly there is more than one way to get to the prop pages...and the one I was using did not show anything smaller than a 13" for my motor. Thanks!

Yes...this prop stuff IS a crap-shoot! I noted the 14x11 prop...That would be at max diameter, but dropping two inches in pitch. With all the "variables" between different props, styles and manufacturers, etc... I'm almost scared to make a change for fear that a second choice will still not be right. I have had numerous aluminum props repaired, balanced, etc...but never a SS prop. Is it possible for a prop shop to effectively tweak the pitch on the prop I already have? ...since I have ran the prop for almost an hour...I'm not sure if ********** will allow me to return it.

Question about your avitar... I've been a pilot for 39 years and have logged 3,700+ hours as a Private PIC. I was trying to identify your avitar. ...sort of looks like a Stinson 108???? ...but hard to tell.

Bamaman1, Yes our local oyster shells will shread an aluminum prop rather quickly. Stainless is the only way to go for me...especially considering the way we use (and sometimes abuse) the toon. With the heaver motor (50 to a 90)...we are sitting lower in the water. I know I will not be able to move through 12" of water like we could before...but I will see what it will do. I haven't thought about the addition of a jack plate. Interesting thought. However...I've got to resolve this prop issue first! Thanks

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

I called this morning about returning the prop. I was told NO. The Rep said they had allowed some folks to return props that had only been run for a few minutes...however, the props were scuffed, scratched, worn, etc. So they have stopped allowing "good faith" returns on a prop that has been mounted. .............sigh..............

I checked with a local prop shop and they will tweak the pitch from 13 down to approximatly 11 - 11.5. Cost is about $100 - $125. That may be my only option at this point.

 

[IslandManMitch]

Re: Repowering 20' Weeres Pontoon... Need Advice

I would rather chew up the blades on my aluminum prop than the teeth on my gears.

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

There are a few words that come to mind...but I shall not go there! Since the used 90 has been on the boat (2 weeks) I have been having problems with idle and midrange. The dealer told me to just run it and they would check it out after the 1st. They are closed until 01/02/12. I couldn't stand it any longer. I pulled the fuel pump off to see if the diaphram was leaking (testing it by pumping the bulb and looking for a leak in the pulse port. What I found was a white foamy goo...yep... water! I pulled the bottom plug and the same was found.

At first I was thinking about a leaking head gasket, which would also cause the same problem. then I started thinking about the goo being at the pulse port. My thoughts have turned to a possible hole in the block. I ran a scope into the cylinder and it has a rusty stain on the walls. I have sprayed some lube in there to help protect it. Anyway...my day has gone down hill!

I am so glad I asked for a warranty...even though they didn't want to give me one. I am going to just push for a refund. I hope your day is going better! Happy Holidays!

FlyboyTR

 

[Silvertip]

Re: Repowering 20' Weeres Pontoon... Need Advice

You have a private message.

 

[FlyboyTR]

Re: Repowering 20' Weeres Pontoon... Need Advice

Well... the 90hp 2-stroke has gone the way of the dinosaur. The dealer refunded my money after finding a hole in the block! Kudos for them. I have now purchased a 2003 Yamaha F90 (four stroke) with 45 hours on it. Everything was clean as a pin. I have mounted it and used the original prop 13x17. I could only get 4000 RPM out of it. I installed the 13.75x13 Solas (the one I purchased for the 90 2-stroke) and trimmed for best RPM I was able to get 4,500. ...still too slow! I am going to try raising the engine up to its highest mounting position (I"m currently in the #2 hole from the top). I am in hopes this will help some. If it's close...I will have the prop repitched.

Second thing... My boat is rated for a 90, but there is nothing regarding the weight of the engine. I am sitting a bit low in the stern. My 12 gallon fuel tank sits on the rear and my two large batteries sit under the rear seat/sofa. I plan on moving the batteries forward and will possibly move the fuel forward as well. I wish I could find a thin aluminum tank to mount under the floor between the joists! Any other suggestions would be appreciated! Thanks.

OH...I'm really enjoying the F90. Very smooth and I can't hear it when it's idling...and I can carry on a conversation while underway. Yea!


EDIT: I have raised the motor to the highest (actually lowest...) mounting hole! It is now sitting as high as it will go. Hope to have her in the water on Saturday. I will report on the changes.