[sunedog]

I need a new motor for a 21' Sun Tracker pontoon with 24" tubes. It had a 60 HP Mercury Bigfoot on it. Can anyone tell me the estimated projected top speed with a 50 HP, 60 HP, 70 HP and 90 HP?The local Honda dealer commented the 50 HP was probably the best choice because as the HP goes up, so does the weight resulting in only marginal increase in speed. I'd like some data to support this.Thanks in advance. This is an excellent forum.

[mistermoon]

It's tough to get a 'toon to go fast. Unlike planing hulls, they don't get "over the hump" and pick up a lot more speed with the addition of horsepower. They just shoulder more water out of the way and go only a little bit faster. We've got a 27' Suntracker (not the Party Hut) with a 115 OB. Wide open with a light load the best we've seen on the GPS is a tick under 24 mph. A friend of mine has a 22'er with a 135 I/O that runs about 28 mph. I've tested a Tracker PB 25 with a 60 that got to 16 mph and change. Even with a 90 on your boat, I wouldn't expect much over 28 mph. I'd expect a 60 BF would get you to close 20 mph. Another thing to consider is that if you go up in HP, you also go up in fuel burn. A good rule of thumb for gasoline engines is to figure at WOT, they burn 0.1 gallons per horsepower per hour. That is to say at WOT you can expect a 60 horse motor to burn about 6 gal/hour, and 115 horse motor to burn nearly 12 gal/hour. Going up a bunch in horsepower will increase your top speed a little bit and may cut your mileage by a lot.Here's what Tracker says on their website for their current 21' 25 HP = 13 - 14 mph 40 HP = 15 - 18 mph50 HP = 18 - 20 mph60 HP = 21 - 22 mph 75 HP = 22 - 24 mph 90 HP = 25 - 26 mph

[BillP]

I have a 20' MonArk pontoon with 50hp 4s Mariner (same as merc/yamaha) and it reads 19.5 mph on the gps with 24 gals of fuel and 2 adults aboard. Put 6 people and picnic stuff aboard and it reads 14 mph. It isn't a bigfoot motor.

[sunedog]

Thank you both.

[rickdb1boat]

Best to go with the Max. HP the boat will allow if you can afford it. You will not regret it, especially on a toon. You will also put less strain on a bigger motor and use about the same amount of fuel, as you will be running lower RPM's at cruising speed. This comes from firsthand experience...BTW- My toon with a 70 HP Evinrude will do 24 MPH full out. I usually cruise at 18 MPH and use about 4 Gallons an hour, if that much...