Pontoon Boat & Deck Boat Forum

While breaking in this engine I am finally to the point where I can run it at WOT for small periods in time. I am only getting 5000 RPM. According to Mercury I should be hitting 5700 RPM's. The boat had an almost full (20 plus gallons) tank of fuel. Also I figured we had around 1000 LBS worth of passengers. I will be buying an extra prop soon and was curious if I should consider going to a different pitch and/or a 4 blade prop and use the OEM prop as a spare?

What size engine do you have, and what is the current prop size? That would give us a baseline to figure out where to go from there.

It is a 50Hp Mercury Big Foot with a 14x11P prop.

You need to test your setup with a light load, 1 or 2 people, 1/2 tank of fuel, one cooler full of test beer...

I think you will be pretty close to max rpm with the test set up, and as you add load to the boat your rpm and speed will drop.

Now, if you plan to use the boat loaded most of the time, a second prop would be a good idea, going down to a 9 pitch would be a good start.

Then you can use a different prop for light load[original] and the lower pitch for loaded boat.

Thank You! Will try that setup shortly and will advise!

You've got 2,000 lbs (dry weight) with just 50 hp. Figure 120 lbs for a tank of gas. 30 lbs, ice chest. 1,000 lbs passengers. Around 3,150 lbs total. That's a lot of weight for a (relatively) low hp engine. You might be propped right, just pushing that little 50 to its limit.

I've got the same motor on a 20 foot two-tube Bentley that currently has a 14x9. I can easily wrap it up to 6200+. That's with approx. 450# in people, 140# in fuel, and around 75# of gear and coolers. Will be switching to a 14x11 as soon as I get a chance. The 14x11 is what both the Mercury prop selector and the Turning Point prop selector say should be on my rig (14x11 for approx 5800 RPM WOT).

cvslawrence wrote:You need to test your setup with a light load, 1 or 2 people, 1/2 tank of fuel, one cooler full of test beer...

^^ That's a critical um... tool right there, every bit as important as a 1 1/16 prop nut wrench. ^^

5000rpm with a good size load on really isn't too bad, You might look into a 14x9 4 blade for those heavy load days, should act like a 14x10 3 blade would have which will add ~300-400rpm.