Prop too low?

[ShinerInTx]

Hi guys,
First time posting. My kids are just starting to get old enough that I could justify having a boat again, and I bought a gently used 2014 Lowe SF214 w/ a 115hp Mercury. I was unimpressed with the speed on this baby during test drive, we made it all the way to 20 mph. The previous owner stored it on the lake, and the toons were coated with moss, so I figured that was most of the problem. After cleaning I only got to 23 mph (gps). The rpm's are only at 5200 at WOT. I forget the exact numbers, but it should be 5600 to 6400 if I remember the manual correctly. So, I started looking at prop calculators but a lot of the recommendations were for about the same prop I have (4 blade, 13.4 X 15). I called Mercury, and the rep suggested looking at the height of the motor before changing props. So, when we took it out this last weekend, I had my wife drive so I could go check the motor out. The motor looks low to me, but even more concerning is that it was actually spraying water forward back on to the fuel tank and on the cowling. After some internet browsing, it looks like the ventilation plate should be even, or slightly lower than the bottom of the mount? If so, I'm probably 3 to 4" low. The motor is all the way down now. I have 4 holes it can go up. I probably won't attempt this myself, don't have the right tools. So I'd like to get it right the first time. Should I raise it and how much? Sorry for the novel.

[wwind3]

Yep! Move it up till cavitation plate is even with the bottom of the motor mount. With the lifting strakes it should perform very well. Good luck.

As you can see from my sig--I have hit 29 gps with no lifting strakes. Just had my prop reworked--hit 27 with 2 aboard and bimini top up--so you should hit at least that. Use your trim button to get the nose up and rpm's. I am running a 16" pitch prop and can hit 5800(redline) easily.

[Soonertoon]

I had the same problem on my 2 log toon. Was set in the bottom hole and was literally puking water up the entire front side of the motor at speed. Raise it up AT LEAST 2 holes. There's a fine line with this as one hole too high and you lose your trim out ability real quick. You might be pushing it at 3 holes up. you can certainly try it and if its too high , have it dropped one. You will see a noticeable difference not only in performance but also in the effort it takes to turn the damned thing.
I have a 22 ft. G 3 Suncatcher , 2 log , no strakes with a 115 Yamaha. 13.25 x 12 P stainless screw. With 3 people, 1/2 tank fuel and calm to light chop water I can pull 27-29 MPH on the GPS. Raising mine up made a WORLD of difference for the better.

[rancherlee]

How much can you trim the engine before it "blows out"? Does this pontoon have under skinning? At 23mph your probably just getting up on the strakes and you might need to trim out quite a bit to get the nose cones up out of the water to pick up speed.

[Bamaman]

Pontoons are a complete compromise of sorts. Get the motor too high and it'll ventilate. Get it too low and the front end might plow thru the water too much. Sometimes, the difference between right and wrong might just be 1/2 inch.

The goal should be to where you can pull the redline of about 6000 rpms with half a load of fuel and 2 people--marginally loaded. I'm talking 6000 rpms--no more and no less when you trim the engine up to a normal level. This may require raising the motor AND putting a different prop on the boat.

The second goal which often brings the engine height mainly, and that's whether the boat will turn a tight turn with the power trim in a low setting without ventilating. This is mainly related to engine height.

But before you start all the hassle of raising the motor and changing the prop, completely clean those toons--even if it requires chemicals and/or lightly sanding the hull. Unless it's clean, your efforts may be wasted.

[ShinerInTx]

Thanks for the feedback guys. When we were out this last weekend. I moved the trim up and down at WOT to try and find the sweet spot. I trimmed it up enough at one point that it felt like it didn't want to raise further (somewhere higher than 1/4). I guess the resistance at speed? In any case, it never blew out. The sweet spot for speed seemed to be at around 1/8 on my gauge. The pontoon does have underskinning. Sounds like 2 holes may be a good place to start depending on how that puts the vent plate relative to the mount. The boat mechanic I like to use cant fit me in until Saturday. Of course I was hoping to be on the lake Saturday.

As far as cleaning the toons, I let the moss dry and brushed it off with a plastic brush. I realize it doesn't look pretty yet, but it feels smooth. You think it's still having a negative impact? Somebody recommended Dynobrite to me, but said it would stain the carpet on the trailer. What's the best approach to this without giving my trailer a lot of character?

[rancherlee]

you have a wonderful lifting device right above the motor. I hook a pair of ratchet straps to my ski bar to raise my engine up or down. I believe your prop is probably the correct one for your toon and raising the engine up should bring you significant gains. Hard to tell from the pictures but I can't tell if you have the "old" 1.7L or the "new" 2.1L 115, the 1.7L is pretty doggy for a 115 and the 2.1L is a powerhouse. Neighbor at the lake has the old 1.7 115 on his straked 2 tube and it will run 33-34mph with just the two of us on it, his has inner and outer strakes.

[Soonertoon]

While clean logs, free of "toon skank", will make a difference in how they glide thru the water, your issue is motor height. Pure and simple. You can clean those logs till you scrub holes in them and it wont change your issue until you raise the motor to where it should be.

[teecro]

you have a wonderful lifting device right above the motor. I hook a pair of ratchet straps to my ski bar to raise my engine up or down. I believe your prop is probably the correct one for your toon and raising the engine up should bring you significant gains. Hard to tell from the pictures but I can't tell if you have the "old" 1.7L or the "new" 2.1L 115, the 1.7L is pretty doggy for a 115 and the 2.1L is a powerhouse. Neighbor at the lake has the old 1.7 115 on his straked 2 tube and it will run 33-34mph with just the two of us on it, his has inner and outer strakes.

1.7 Liter

The 2.1 Liters look much more angular...