11mph with a 50hp

[cicora]

Today was the first day I've been able to run my toon with a GPS to see how fast I was going. The results were a bit surprising and dissappointing. I was running 11.2mph WOT and 8.4mph WOT. I thought I would hit around 15MPH towing someone and 17-20mph not towing anyone. I have a 20ft Playtime boat. The engine is a 1985 50HP mercury outboard. I have 23" logs. My trim is manual, and I've tried it both in the 2nd hole and 4th hole. The toon had myself, my wife and two kids. I have no info about my prop other than it came with the engine and it has three blades. The edge of two of the blades is a little rough. Were my expectations too high or is this not normal. I was passed today by another pontoon with a 50, which made me think something is amiss? Any hints or suggestions would be appreciated. Thanks.

[margaritaman]

When I had a 50hp on my 22' with 23" logs I was getting about the same as your speed. The lower figure when loaded and the higher figure with 4 adults that is why i switched to a 115hp. I get 27 mph with 4 adults on the 115 at 5000rpms.

[ROLAND]

Cicora

I also have a 20 footer but with a 75 hp. also the logs on my boat are 25". I can tell you under perfect conditions, just me and my wife on the boat, no chop, I am hitting 25 mph ( by gps ). I'm sure the larger logs may help a bit but I was wondering... were any of your passengers up front. that could help slow you down a little bit, plus If I read your post correctly, your motor is 25 years old. It's possible it's lost some of it's compression over the years. Just something to think about...

[lakerunner]

Those old motors were HP rated at the powerhead not the prop shaft as today's are. You prob have about 40 hp if that.

[toondog]

I don't seem to lose any speed when towing water toys. If you take weight off the plowing toons and put it on a plaining tube (the water toy), why would you lose speed?

[jim454]

Those old motors were HP rated at the powerhead not the prop shaft as today's are. You prob have about 40 hp if that.

That's a good point.

My top speed is 18 mph, I could use a new prop though. 18ft, 50 honda. That's with just me onboard.

[WaltF]

Are you able to reach WOT with that prop?

[cicora]

I have gauges at all, so I'm not sure what RPM I'm at when I have the throttle wide open. I talked to a mechanic friend of mine and he suggested making sure that the the carbs are opening all the way when my throttle is down and he can also check the compression for me.

[Stephen]

I've got a 50hp Yamaha on a 2007 21' Sweetwater and I'm supposedly hitting 25mph. Now, no one on this site believes that, but my friend ran his boat side by side with me for a while and watched his mph reading and told me that's what I was doing.

It's a newer motor, though. Conditions on the lake were perfect, and I only had three people on the boat including myself (200lbs), my wife (95lbs), and a buddy (250lbs).

Hope that helps.

[margaritaman]

Is your speed on GPS or speedometer?

[slingshot]

That's a very valid point about HP rating back in the eighties. I'm sure your engine was only putting out 40 or so HP when it was new. Assuming your motor has never had a rebuild; It's 25 years old which will no doubt reduce your HP even further.

[cicora]

25 is really fast for a 50hp. In the toon are my kids (40 and 60 pounds) myself (170) and my wife (140). So about 410 pounds total. The toon weighs 1100 pounds. I'm going to check the compression and make sure the throttle is opening up the butterfly valve's all the way. That's about all I can think of right now to do.

[HandymanHerb]

My 1991 50 will do 16 mph GPS with the prop guard, 17 without it, but I don't miss the 1 mph with the extra control I have at slow speed and for going through shallow water with the engine trimmed up and shooting water like a jet boat.

Plus it saved my prop twice from hitting gators in the head with the engine and was nicer to the gator too, getting hit with plastic beats the prop.

[FloterBoter]

that still seems slow to me. i know a guy with a 24' toon with a 70 hp johnson and he hits about 23 or 24 mph.

you need the right prop. and to get the right prop, you have to know your rpm. otherwise you have no way to tell your rpm at WOT. the engine is rated based on a certain rpm range at WOT. i would get a tach (even one of those external ones would work) and then make arrangments with a local prop shop to swap in and out some used props. try going up and down in pitch and see what happens. find out at what pitch you start to get bad blowout of the prop. every boat is different and the right prop makes all the difference in the world.

[limulus]

I've got a 50hp Yamaha on a 2007 21' Sweetwater and I'm supposedly hitting 25mph. Now, no one on this site believes that, but my friend ran his boat side by side with me for a while and watched his mph reading and told me that's what I was doing.

It's a newer motor, though. Conditions on the lake were perfect, and I only had three people on the boat including myself (200lbs), my wife (95lbs), and a buddy (250lbs).

Hope that helps.

Now this is the kind of info that blows my mind! Is your friend using GPS or a speedometer to measure your speed? I have a 24' boat witha 115HP 4-stroke and the fastest it has ever gone is 24MPH and that is with GPS. My brother has the same boat as me with a 50HP 2-stroke and I don't think his boat will go over 15MPH.