Pontoon Boat & Deck Boat Forum

Went out yesterday with seven big folks onboard. We're not talking any slim bathing beauties here. The boat was also loaded with eight various sized coolers. All loaded with brews of your choice, although mine had Dr. Pepper, Water and flavored vitamin water - after all, I'm the Captain and the one that has to get the boat back on the trailer at the end of the day. I was wondering how much prop slip I was experiencing. We did a lot of fast runs across the lake in rough conditions (north winds all day 10-15MPH). We had a great day tubing, wake boarding, and floating around on a new sand bar (lake is down 3.25'). My prop is a Solas stainless steel 14.25x17, RPM max was 6200, and top speed was noted at ~34MPH. So how do I figure the % slip and are there any props that I might consider for doing a better job with this Yamaha F225?

http://www.go-fast.com//Prop_Slip_Calculator.htm is what I have used for years. You can nail it down to a knats ass!

What is your hull configuration? What kind of speedometer are you using to figure the speed?

Speed was using gps. It's a 2007 Bennington 25' triple toon (25") 6 strakes.

Using Brian's link, I get slip=32! What kind of prop could do a better job? I'm suspecting that on a pontoon boat high slip is just a fact of life when heavily loaded.

I got the royal thrashing for saying I had 8 big folks on board. I had a 9th tanning bunny on the back for ballast - my 39 year old daughter. Man did I catch hell for that!

With three 25" toons (with strakes) and a decent prop slightly over the redline, I would think you'd be seeing 40-42 mph. I think you're short on speed vs. so much horsepower.

Are you trimming the engine up on your speed runs to lift the nosecones? The speed comes from getting the nosecones out of the water.

If you're trying to get it faster, the prop might be the place to start. It'd be nice if you could find someone with a Reliance 17 pitch prop to try out. And if you're not using a GPS to check the speed, you need to do so.

Ken, I just ran a 15X19 Mirage Plus yesterday, with the plugs removed. It came in at 12% slip. I was impressed! Top speed was 52 at 5800. Too much pitch yet, I wanna be running 6400. I'm gonna try a 15 1/2 X 17, try to get to 62 to 6400 range. Rev limiter is set for 6400.

Have you considered varying your motor height?

Drago wrote:I got the royal thrashing for saying I had 8 big folks on board. I had a 9th tanning bunny on the back for ballast - my 39 year old daughter. Man did I catch hell for that!

Well tell her that your buddies here (at least this one) think she's very pretty, maybe she'll forgive you.

Of course you got a thrashing! What were you thinking???

Bamaman,

That's what I was interested in knowing. The Reliance prop might just have less slip because of the way it is shaped? Don't know. The motor is all the way down. The boat was heavily loaded especially the front. I could not get the sun worshipers to sit under the bimini with the Captain. Motor was trimmed up just a ever so slightly by feel and sound trying to raise the nose a bit. I have seen 43MPH with the boat clean and lightly loaded. I'm just trying to find a prop that would have better grip when heavily loaded. I know from Brian's many years of experimentation that it can be a costly thing. I'm also considering a chip reprogram but have not considered a 5" jack plate yet. My neighbor has the tools to raise the motor but had not considered that. Was just wondering about prop slip for the various props you others have used.

The larger Diameter bathing beauties require a larger diameter prop.
Its just that simple
FWIW- the 300hp ecu is worth 4mph and 400 rpm on my 250 - Not reflected in current sig.

Edit: IMO the largest diameter prop is ALWAYS the best choice on a toon with substantially varying loads.