Porposing Question

Paul Strombeck

Paul Strombeck

Active member
Bought a new 18' Deluxe Jon since I do a lot of river fishing & hunting. Boat is 1860 Jon with rod boxes, live well etc. In the stern I have 9 gal fuel tank, one battery and Power Pole on Transom. Dual batteries have been move forward. No additional weight distribution is feasible. Boat is powered by 50 HP Merc Tiller.
Boat porposes at 21 mph when I am alone and at 23 mph with one passenger I installed a no drill whale tail device which corrected problem but I can't stand it and don't want to be fighting it with trolling motor in current or weeds. Haven't talked to dealer yet but here is my initial plan.
Remove whale tail
Install manual jack plate to get 4 inch set back and raise motor on transom. Add negative transom wedges to get more angle on transom
Thoughts??
Thanks
........
 
The combination of these should work. Porpoising is due to too much power or too much weight in rear or both. I went the wedge route on a smaller boat and it worked fine. I made bigger than I thought and was able to shave them down to get preferred running angle. I don?t know if you are going to make them out of wood but keep this in mind.
 
I had a porposing problem with my 17' TDB and 50hp Honda. Cured this with a set of aluminum wedges purchased off the internet.
I don't think the older boats had enough transom "rake" or angle.
Sounds like you have already tried this.
 
I should have mentioned that I already have a 4 blade prop on the boat.
Will probably buy the metal transom wedges offered for Merc. Since they are already slotted I should simply be able to slide off the Outboard - insert wedges and re-mount the unit.
If I add the jack plate I should be able to lift the OB some 3 to 4 inches and improve the shallow water performance
Thanks
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in response to your post. that 50 hp is not too much motor for that boat. in regards to the jack plate; I am running a hydraulic jack plate on my 1860 alweld with a 60 hp tiller. I have a full permanent alum blind on the rig for waterfowl hunting I got the JP 7 years ago and it is one of those things that once you own one; you will never be without one again. they are worth their weight. I would not get a manual one. being able to change the motor height while on the move is priceless. I can motor (slowly) in 12" of water with the JP all of the way up.

I have my motor set with the cavitation plate one inch above the bottom of the boat. I am running a 3 blade 15" x 13P prop. 5300 to 5400 RPM trimmed up and running WOT at 31MPH with 3 guys and lots of gear/decoys/dog/LP tank/dual batteries/ect
 
Paul, I would move the fuel tank. even if you have to do away with the 9 and go to a 6 gallon and put if forward of the mid point. I moved my tank ( 6 gal.) forward and carry a spare 2.5 gal pour can (plastic) in a front cubby if I think I am going long runs.

that 9 gallon tank when full weighs 75 pounds that much weight can make a big difference on how a boat will behave.

if you want to test the impact of making that move before you do it. only have a gallon of fuel in the back tank and borrow a 75 pound kid and have them set up front while you make a short run to test the impact. if no kid is available; you can use 3 cement blocks. they weigh about 28# each. if you don't have any; go to the lumber yard buy threee, use them for the test run; save the receipt and return them.

and you didn't say if you had a tach on this rig. if you don't; you need to get one. setting up a boat/motor for optimum performance is impossible without a tach
 
Put the tiny Tach on yesterday. Mounted the tach on the Big Tiller behind the shift. I'll be on the water the next 4 days with a couple of friends so I'll have a chance to see how she rides with more weight in the boat.
 
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