Motor straining, alarm went off first time pulling a tube with 40 hp

[Russ42]

I just bought a tube (winged) which attached from underneath, not the front (can do 360 turns on it, etc.). First time towing a tube with my 40hp Mercury on 16.5 ft Alumacraft Lunker Fishing Boat. Worked ok at 5-10mph, but if I tried to accelerate, there was tremendous drag, boat really didn't go faster, just revved hard, and then my overheat alarm went off until I slowed to a crawl again. Anybody have the same problem? Is it the towable?

 

[rallyart]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

Just too much drag for the little engine. A 'pancake' style tube might be better.

 

[SierraMark]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

I have a 1991 Starcraft 16' Fishmaster with a 1991 40HP Mercury motor and I have pulled a 1 person tube that connects in the front of the tube at 25MPH without any problem.

I have read making sure the tube is inflated properly could help lift the front of the tube out of the water. Maybe check that and if not then try a tube with a connection on the front.

My tube is similar to this one

-Mark

 

[jimmbo]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

Is it a 4 atroke? I learned to ski behind a 14 ft runabout with a 2 stroke 40 hp Johnson. Even learned to do deep water starts on a Slalom ski behind it.

 

[kenmyfam]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

Likely have too much drag for the situation. How big is this tube ?? model number and a photo would help. You may need to prop down some pitch or load the boat differently.
Beware the overheat alarm as well. Should not really happen just from excess drag. How good is your cooling system ??? other reason could be that you were getting that much cavitation going on with the turmoil of the new tube on the back that you were starving the lower unit of cooling water.
My other comment is that you may well be towing it from too low of a position on the boat causing plowing.
Just a few points for you to ponder over.
Good Luck.

 

[Russ42]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

Likely have too much drag for the situation. How big is this tube ?? model number and a photo would help. You may need to prop down some pitch or load the boat differently.
Beware the overheat alarm as well. Should not really happen just from excess drag. How good is your cooling system ??? other reason could be that you were getting that much cavitation going on with the turmoil of the new tube on the back that you were starving the lower unit of cooling water.
My other comment is that you may well be towing it from too low of a position on the boat causing plowing.
Just a few points for you to ponder over.
Good Luck.

The tube is a Sportstuff Bat Xray Model 53-1510 (tried to add picture), a 1 person tube with wings on the side. I haven't had any issues with the alarm except this one time pulling the tube, and the boat performed fine afterward without the tube. My stream hasn't been strong on the indicator stream, but the indicator tube has been getting a bit clogged from being in dirty water where my pier is. Seems okay though after taking a wire to the outlet hole, so believe its just the indicator and not the impeller. I thought about the cavitation too, the stern of the boat was visably pulling back and forth with the tube, making the motor bounce a bit (could tell by the sound of the engine waning then not waning, then waning. I'm really thinking plowing is going on from the tube being attached from the middle of the bottom of the tube rather than the "pancake" style pulled from the front---its off of 77 feet of tow rope. Thanks to everyone for the advice

 

[kenmyfam]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

I think the pulling from underneath is certainly contributing to your issues. That and how high the tow rope is mounted to your boat. Photo makes it look like an easy one to plow. If the water stream is noticably not as strong it is time to investigate. When was the impeller last replaced ??

 

[Russ42]

Re: Motor straining, alarm went off first time pulling a tube with 40 hp

I think the pulling from underneath is certainly contributing to your issues. That and how high the tow rope is mounted to your boat. Photo makes it look like an easy one to plow. If the water stream is noticably not as strong it is time to investigate. When was the impeller last replaced ??

Impeller was replaced last year. I can get a strong stream right after poking the outlet with a wire, then it tapers off.