I'm new here & love the info especially dedicated to pontoon boat configurations. I bought a 2016 20ft Manitou Aurora with the 90hp PS. when I test drove it I had myself, a marina employee & 1/2 tank of fuel (about 12 gal). she ran around 21-23 mph @5200 rpms.
After having it for about two months I'm noticing that it maxs out 4900-5000 rpms, thats with my wife (petite), 9yr old son & cooler (20-25pds max). I keep your average gear on it, nothing crazy...
I read on the evinrude site that the operating range is 5000-5500 rpms. But watching the "Boat Test" video with basically the same set up as mine, they ran it at 5800 rpms.
I'm just wondering if my experience is normal or should I think about a different prop? My prop came with the boat, I believe it is a 13".. Any advice would be greatly appreciated.
Based on your description, I think you need to go to the next lower pitch prop. But, be sure your dealer has mounted your engine at the proper mounting height for your particular rig, first. This is quite important. Just because it was set up that way when you test drove it & took delivery like that, doesn't necessarily mean that your rig is set up for optimal / proper performance for all conditions and the whole season. WOT rpms under typical loading is very important. You should prop it with an eye towards a pitch that will allow you to still stay in the specified WOT range should you have an increased loading situation. Engine height is an important factor in all of this!
Your demo ride was probably done when the weather temperature was on a cooler day in the earlier part of the season. This is probably why the WOT rpms were 200 to 300 higher. In the warmer part of the season, the cooling water and air temps rise & typically will reduce WOT rpms by the amount you are experiencing.
You didn't say what pitch your prop is. I assume by 13", you may mean diameter or pitch? Either way, I would go with the next lower pitch after determining engine height. Toons tend to be on the heavier side and require more power to keep them going. That's why the gear ratios are different in the Pontoon Series, in the first place.
I hope this helps!
As was mentioned in another post, the weather and temperature play a big part in engine power output. Hot summer afternoons lower the horserpower available from a gasoline powered engine.
Pontoon boats also accumulate scum, grass, barnacles, etc. on the pontoons as the season progresses. Even a smooth feeling scum can add drag and slow down a boat quite a bit. Also you may be adding more people or more weight to the craft which also limits rpms and top speed.
See your dealer to check out the running surface of the pontoons and the output of the engine.
A stainless steel prop is not only stronger but it is more efficient than an aluminum propeller.