Motor and prop setup

[Brandon MAXWELL]

I just purchased a 2003 Fisher Freedom 220 DLX 22ft with 26 inch pontoons with a 2010 Mercury 115HP Optimax with a 13.5 Diameter 17 pitch SS propeller. The motor was checked out and parts replaced recently before I would buy it. I don't have any past references on how it ran before me. The issue is at WOT my RPMs never get above 4500. If I adjust the trim beyond 4-5 bumps then the motor will lose power and I trim down. Once I shift to neutral I can power back up and she runs fine as long as I trim down a bit. RPMs never spike. At 100% trim down the motor runs perfect but only at 4500 RPMs. Speed is calculated by GPS at 21. I think I need to reduce pitch based on articles and vids I have watched. Any suggestions? Max RPM according to some Mercury manuals I have found suggest 5000-5500/5750???

 

[clemsonfor]

I would say just by looking at it on paper that you should be running a 15p prop. Unless there is something mechanically wrong with the motor as well your sea trials say to also reduce your pitch to a 15p but also maybe reduce the diameter by a touch.

Something is for sure wrong though. If your 22ft boat can only go 21mph with a 115hp motor. With just me on my 22ftish pontoon and a 60hp two stroke I can hit 21mph with just me on the boat!

 

[HotTommy]

First off, many people have come to this forum to ask about a recently purchased used pontoon boat that is not as fast as expected. You can learn a lot by searching for and reading some of those threads, several in just in last few months.

Second, there are several things that can cause a boat to go slower than optimum and you may have one or more of them. They are:

• Poor engine performance (e.g., inadequate fuel, igntion, etc.)
• Poor propeller performance (e.g., wrong pitch, diameter, blade count, or slipping hub)
• Excess drag on the boat (e.g., motor too deep in the water, hidden weight (e.g., water in the logs), large sail-like bimini top, etc.)

Generally speaking the best way to diagnose the problem is with facts and not guesses. For example, you'll need actual RPM and GPS speed on still water with little wind. I'd start by being certain the engine is running correctly. Next, check that your engine is mounted at the correct height. The most commonly recommended starting height is with the cavitation plate even with the bottom of the engine pod (that large canoe shaped piece that supports the transom and engine). When you are sure of that, go to the Mercury Prop Selector website, enter data for your boat and see what prop is recommended, and what speed is expected. Compare that to yours. If yours is not close to what is recommended, consider replacing it. .... Finally, when all the above is where it should be, if you are still too slow, look for hidden drag such as water in a log. There are lots of threads here about checking for and removing water, and pressure testing logs for leaks.

Good luck with your boat.

 

[ahicks]

Assuming everything Tommy mentioned checks out (my bet is it will), I agree on the prop issue. 17" of pitch on a conventional 'toon is too much. 15" should work though, and take you up to 25ish mph.

Trim is pretty much useless on a toon as compared to a runabout. You may feel/see a difference in ride, but picking up more than a mile or two mph would be a surprise.

 

[Brandon MAXWELL]

Great information and I appreciate the help/advice. I have been reading alot of the posts about props and such on the forum and they are helping a lot. I can rebuild an engine on a four wheeler but when it comes to boats and motors I am as dumb as a turnip.

 

[ahicks]

I'm guessing you had a question or 2 prior to getting the quads figured out too. Nobody here looking down on that practice!

 

[Brandon MAXWELL]

Lol I sure did................