Johnson 8hp struggling planing, something wrong?

[BoatFisho]

Have a 2000 model sitting on a zodiac c285s (solid floor). With about 300lb in the boat.

The engine will plane eventually in a dead flat sea, if we both sit right up the front. It takes about 30-40 seconds to get on plane though. When it goes over small swell when on plane it will rev like the propeller is out of the water, not always just some times, I also notice this when turning. It runs great, starts first pull and pisses water out beautifully.

Does that sound right? Its almost like it has no hole shot, where as an 8hp yammy on this boat has taken off and onto plane much quicker.

 

[BoatFisho]

Re: Johnson 8hp struggling planing, something wrong?

Just noticed the previous owner had the tilt pin set to the 3rd furthest from the transom. Im presuming this wouldnt have helped.

 

[boony_124]

Re: Johnson 8hp struggling planing, something wrong?

Try your trim pins. Moving the prop closer to the outboard one pin at a time and taking for a spin. You don't want to go too far as this will cause it to tilt too far. Will drop your top speed and load engine. Therefore one adjustment at a time until you find the "sweet spot"

Different outboard may have had a slightly different prop or even the mountings were slightly different so need to set trim..

Other thing you can try are Hydrofoils. Only about $35 but are like wings above the prop and help to get it up to plane. Made a difference on my old mans boat. He has a 3.9m with a 30hp. His tinny is early 80s and is really heavy. He weighs in at 110kg and the back and he carries excessive weight in the boat. Made a difference with his. Worth a try after adjusting the trim.

Cheers

 

[BoatFisho]

Re: Johnson 8hp struggling planing, something wrong?

thanks boomy. ive been looking at foils, the cheaper ones require holes drilled through the cav plate, bit wary of that, as i need to throw this in the boot of the car after using.

 

[OptsyEagle]

Re: Johnson 8hp struggling planing, something wrong?

Definitely look at the trim pins as boony indicated. In my 14' Springbok with a 15Hp motor I constantly set mine depending on the load in the boat. From the transom out, I set mine at 3 if two people are in the boat, 2 if I am alone with a trolling battery up front or 1 if I am alone without any weight up front.

If I left it at 1 with a full load, I doubt it would plane and if I leave it at 3 when I am alone, I know it will bob up and down slapping the water, if I open up the throttle wide open.

 

[BoatFisho]

Re: Johnson 8hp struggling planing, something wrong?

took it out today and tried all 4 pins, none of them helped it get me up on the plane. was about 250lb load (me and tank) and the boat (80lb). perhaps a zodiac 285 is just not a planing boat and i am pushing it past its expectations, but i expected an 8hp to push me by myself ok.

 

[BoatFisho]

Re: Johnson 8hp struggling planing, something wrong?

its a lot worse in any kind of swell or chop, in a following sell it really bogs down. when on small swell it will often go to plane, then stop, then almost like its got turbo charge will take off and rev freely and i have to pull the revs off to keep it from being squirrely. i dont know how some people get this boat to plane with a 6hp 2 up.

 

[BoatFisho]

Re: Johnson 8hp struggling planing, something wrong?

have decided to get a bigger boat.

 

[slate1234]

Re: Johnson 8hp struggling planing, something wrong?

I think a bigger boat is what you need, I have a 2.75m (9ft) with inflatable keel with just me in 13.5 stone (189lb) I get upto 23mph on the gps, add another adult and it just plough's, I have had my evinrude 8hp on a 3.2m (10ft) with two adults and it gets on the plane no problem, I think it is a lot higher in the water, as for useing it in any kind of swell I dont feel safe at WOT I just back right off,
good luck

 

[boobie]

Re: Johnson 8hp struggling planing, something wrong?

What's the boat rated for horse power wise ??

 

[BoatFisho]

Re: Johnson 8hp struggling planing, something wrong?

thanks slate, im thinking 3.2 or 3.4 as well. it can plane with 2 up, but not as quickly as id like. i guess these boats werent made for slicing through chop either so i need to be realistic there.

hi boobie, its rated to 8hp. i didnt want to go more simply because i have to put the engine back in the boot after each trip