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pontoon with 70 hp johnson
Posted: Mon Jun 26, 2017 10:15 am
by cds111
hi, I recently bought a 1993 sweetwater 24 ft pontoon without an engine on it. I also recently bought a 2000 Johnson 70 hp and put on it. everything seemed fine with just me and my wife on it but when more people and more weight it really struggles and uses a lot of fuel. I did some research and found that the motor is supposed to be installed with the cavitation plate even with the boats transom. I didn't know this when installing the motor and put it down as far as it would go which is about 6 inches below the transom as the motor is a long shaft. what negative effects will there be having the motor this low? I plan on raising it up soon but just wanted to know what problems it would cause? thx, chris
Re: pontoon with 70 hp johnson
Posted: Mon Jun 26, 2017 10:25 am
by JLester273
I'm sure someone with more knowlege than me will come one soon. However, I have a 1988 Harris with a 1997 Force 75
I'll have to look at my picture (unfortunatly my boat isn't close.) to see where the cav plate sits. Mine will do 18-19 mph (GPS) with 7-8 people on-board.
So I think your on to something bringing it back up. Mine has some space to go lower so I know it is up high compared to yours
best pic I have on this machine
- IMG_1030.JPG (281.95 KiB) Viewed 8570 times
Re: pontoon with 70 hp johnson
Posted: Mon Jun 26, 2017 12:42 pm
by MH Hawker
it should be just under water when your running, lower may add drag and slow you down a bit
Re: pontoon with 70 hp johnson
Posted: Tue Jun 27, 2017 5:37 am
by Bamby
Does your boat have a tech? If so what are the numbers? Most of the issues you are describing also can reflect back to your prop. If you're attempting to run too tall of a prop performance may be marginal but acceptable under a light load and get progressively worse when loaded just as you're describing. If it's bad enough you might even get a whiff of raw gas exiting the engines exhaust because the so loaded up and lugging that it simply can't burn it all cleanly. If this should be the case you really need to get it cleared up before serious harm comes of your motor.
Re: pontoon with 70 hp johnson
Posted: Tue Jun 27, 2017 6:14 am
by curtiscapk
Yes you need a TACH so we now your RPM's.....
Re: pontoon with 70 hp johnson
Posted: Sat Jul 01, 2017 5:12 pm
by cds111
thanks for all the replies everyone. I tried moving the engine up but it didn't help. I also tried going from a 14x11 prop to a 14x9 and it didn't help either so I sold the motor and I'm going to put a 115 hp on it as 115 is max rating for my toon. thx again, chris