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2022 20LLG SPS and F115 Yamaha

Fairway

Fairway

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After dealer setup and following the break-in period of our boat July '22 it was running 34mph @6100 RPM WOT. Over time now it runs no better than 25mph @5400.
Is it typical for max throttle and speed to drop over time? I have the boat out of water and plan to pressure wash the tubes but it doesnt seem there is that much on them to create that much drag. (I dont see any tube drain ports - does Bennington not install them?)

Solas Saturn 3 Blade 13-1/2 X 15P Propeller and motor is in lowest hole (all original dealer setup)
Thanks for any help.
 

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That doesn’t sound normal to me. I have had a Yamaha F115 on two boats for +20 years and never had a decrease that wasn’t related to fuel, spark plugs, weight, or water / wind conditions.
 
Pbakk said:
That doesn’t sound normal to me. I have had a Yamaha F115 on two boats for +20 years and never had a decrease that wasn’t related to fuel, spark plugs, weight, or water / wind conditions.
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Out this afternoon on flat water no wind. I began to notice the decrease last year. It runs strong and smooth, new plugs, fresh gas, oil and filter.
 
Typically I would think dirty pontoons first, or wonder if there is a leak and water in any of the pontoons second.

You said they are not too dirty, but do you have any pictures of your pontoons? It doesn’t take much algae or scum build up to significantly impact a pontoons performance. I’ve seen them impacted a lot more than just 9 mph and 700 rpm due to dirty pontoons.

Are you able to put it on a trailer and check for water in your pontoons? There isn’t a drain port put into the pontoons. However, if you have a leak and any pontoons are collecting water in one of their chambers, a good aluminum welder can drill, drain, weld leaking area(s), and put in a drain plug. We had that all done under warranty back in 2020 on our pontoon with some seam weld problems along the performance foil on our port side pontoon. It’s been good ever since.
 
Did you hit something with the prop to throw it off a little?
 
Vikingstaff said:
Typically I would think dirty pontoons first, or wonder if there is a leak and water in any of the pontoons second.

You said they are not too dirty, but do you have any pictures of your pontoons? It doesn’t take much algae or scum build up to significantly impact a pontoons performance. I’ve seen them impacted a lot more than just 9 mph and 700 rpm due to dirty pontoons.

Are you able to put it on a trailer and check for water in your pontoons? There isn’t a drain port put into the pontoons. However, if you have a leak and any pontoons are collecting water in one of their chambers, a good aluminum welder can drill, drain, weld leaking area(s), and put in a drain plug. We had that all done under warranty back in 2020 on our pontoon with some seam weld problems along the performance foil on our port side pontoon. It’s been good ever since.
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Yea... i guess "not too dirty" is a relative term! I have it out of the water so i'll pressure wash them and see. Any tips on a product to get them clean? I would think if it were drag the RPM's would still get up to 6100 where it used to get up too?
As far as the tubes I'm not sure how to check them even with it on the trailer. The boat sets even in the water (always sat a bit ass heavy but thats a given).
 

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When it is on the trailer, stand beside it and have somebody move the rig a foot and hit the brakes. You can hear water sloshing. Been there done that.
 
Go to napa and get aluminum cleaner. Those toons are really dirty. That will shave off some mph fast. I use it in a garden sprayer. Spray a nice even coat on, let it sit for a min or two then hit it with a pressure washer. its a little bit of a learning curve to not get streaks but it works amazing.
 
Fairway said:
I would think if it were drag the RPM's would still get up to 6100 where it used to get up too?
As far as the tubes I'm not sure how to check them even with it on the trailer. The boat sets even in the water (always sat a bit ass heavy but thats a given).
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Dirty Toon Reply: Nope….RPM’s and MPH drop when slowed by scum, build up, barnacles, etc…. So your symptoms are correct for that problem, but that doesn’t exclude it being caused by something else.

Informal Checking for Leaks: If on a trailer, have one person move forward and stop. Another listening along pontoons. If there is water in them, you’ll hear it “slosh” around. Dealership/Welder will actually pressure test them by putting soapy water on them and adding 1-2psi to see if it bubbles anywhere to pinpoint leaks.
 
FYI: Those toons look VERY DIRTY in your picture. Feeling confident that is your entire problem right there. I would clean those REALLY GOOD first, and then water test. After examining your picture, I have to believe that’s your problem. And yes, but sorry, those qualify as very dirty. It really drags down rpms and mph and performance when they get like that. All the more so with a 115hp motor which doesn’t take much to go from performing really well to booged down on a pontoons/tritoon.
 
Seadoorxpguy said:
Go to napa and get aluminum cleaner. Those toons are really dirty. That will shave off some mph fast. I use it in a garden sprayer. Spray a nice even coat on, let it sit for a min or two then hit it with a pressure washer. its a little bit of a learning curve to not get streaks but it works amazing.
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Ive used similar on previous boat...really gets the "stain" out for sure. Im going to pressure wash the bulk off first then I may get some tomorrow and do a final clean when i can park it across the street so not to get it on driveway or grass.
Vikingstaff said:
FYI: Those toons look VERY DIRTY in your picture. Feeling confident that is your entire problem right there. I would clean those REALLY GOOD first, and then water test. After examining your picture, I have to believe that’s your problem. And yes, but sorry, those qualify as very dirty. It really drags down rpms and mph and performance when they get like that. All the more so with a 115hp motor which doesn’t take much to go from performing really well to booged down on a pontoons/tritoon.
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I dont have a boat lift so its in the water most of the time. Will PW them and find out tomorrow or Saturday for sure.
 
Ive got all the algae off accept under the bunks. What a PITA to get all up underneath those 3 tubes! (Previous boat was not a tritoon and a lot easier to clean the tubes).
 

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Those toons are really "dirty" and I am sure your drop in speed could be associated to that. As mentioned, if you rock the boat side to side at the stern of the tubes while on the trailer and listen, you would be able to hear "sloshing" of water back and forth if there is water in the tubes

As a secondary check, you can pour " hot water" from a bucket from the top of pontoons and let it run down them and if you notice a temperature change from hot to cold as the water trickles down the aluminum pontoons, then you can have potentially water in the toons where it feels cold.

When we used to park at a sandbar, I always got out the green and yellow scotchbrite pads and scrubbed above and below the waterlines of the tubes to keep them a clean as possible between haulouts over the summer.

Good luck! Hopefully you are good to go now that you got them cleaned.
 
Got her back in the water after good overall cleaning, tube power wash, oil, filter and lower unit gear oil change.
Cruising at WOT was 5800rpm 32mph so much improved after cleaning the tubes. I guess its the regions under the bunks that i couldn't get to not allowing it to get where it was new but it plenty fast enough for me!
 
Fairway said:
Got her back in the water after good overall cleaning, tube power wash, oil, filter and lower unit gear oil change.
Cruising at WOT was 5800rpm 32mph so much improved after cleaning the tubes. I guess its the regions under the bunks that i couldn't get to not allowing it to get where it was new but it plenty fast enough for me!
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I thought cleaning those tubes would get you taken care of. Glad you got it back up there closer to new. Any build up on tubes just kills performance.
 
Glad to hear that your performance has improved.

One additional thing I noticed was that you’re running a SS prop on a 115 hp. engine. Typically the rule of thumb is to use SS starting at 150 because of the weight. As such, that might also be a factor.
 
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