35 johnson planing help

huntingtheworld

Petty Officer 1st Class
Joined
Jun 13, 2010
Messages
254
1979 35 hp johnson with a stock prop and a 10.5x11 prop
motor is a 20 inch shaft and boat has a 21 inch transom.a pic of the boat is in my profile.

Im having problems planing with 2 people.it almost will go on plain but no luck.im trying to figure out what i can do with out having to change the motor.
 

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: 35 johnson planing help

A prop with less pitch should help. Props are available in 10 and 9 pitch.

That looks like your typical 15-1/2 ft tri hull boat which are usually rated for about 70-80 hp.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: 35 johnson planing help

I can't tell anything from your picture.Sure would help to have a description of your boat. Year,brand and model, size..
If you could get it to plane we could tell better what prop is needed.
Have you tried putting your passenger forward,temporarily moving gas tank forward,Move the battery as much as cables will allow.temporarily eliminate as much weight as possible, trim down for hole shot.Check that the carb opens all the way.
If your close to planing a few pounds hear and there could make the difference.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: 35 johnson planing help

Is this a new boat to you or a new problem. As Mr. Jestor said, the engine is marginal. I think the recommendations are for at least half the hp on the BIA rating decal. Back in the day, you never saw less than 60 hp on one of those boats.

Mark
 

huntingtheworld

Petty Officer 1st Class
Joined
Jun 13, 2010
Messages
254
Re: 35 johnson planing help

the boat is a 72 trident fish and ski 14 foot.The boat will plain out with 2 people with no gear and will do about 22 mph.with gear 9.9 and will not plain.Ive moved people and gear around and still the same.
Yes a newer boat someone gave to me.Carb is open and motor runs perfect.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: 35 johnson planing help

the boat is a 72 trident fish and ski 14 foot.The boat will plain out with 2 people with no gear and will do about 22 mph.with gear 9.9 and will not plain.Ive moved people and gear around and still the same.
Yes a newer boat someone gave to me.Carb is open and motor runs perfect.

The light load of 2 folks and 22 mph sounds ok. The loading up is what plagues smaller engines. Back in '72 FG boats were pretty much just gutted hulls and there wasn't a lot of weight. Worked ok with the smaller engines. I don't know what to tell you. I assume the hull is a modified V with a pretty much flat transom hull area, maybe soft chines (rounded at the lower corners of the hull vs sharp angle). Assume bottom is clean, no algae, moss, or barnacles. Assume you have tried different tilt pin positions along with your moving things around in the boat. Assume prop is standard equipment in reasonable condition.

Mark
 

huntingtheworld

Petty Officer 1st Class
Joined
Jun 13, 2010
Messages
254
Re: 35 johnson planing help

The light load of 2 folks and 22 mph sounds ok. The loading up is what plagues smaller engines. Back in '72 FG boats were pretty much just gutted hulls and there wasn't a lot of weight. Worked ok with the smaller engines. I don't know what to tell you. I assume the hull is a modified V with a pretty much flat transom hull area, maybe soft chines (rounded at the lower corners of the hull vs sharp angle). Assume bottom is clean, no algae, moss, or barnacles. Assume you have tried different tilt pin positions along with your moving things around in the boat. Assume prop is standard equipment in reasonable condition.

Mark

yep bottom of the boat is clean and waxed props are good.i have tried moving stuff and tilt and it makes it worse.
 

craze1cars

Lieutenant Commander
Joined
Dec 26, 2004
Messages
1,822
Re: 35 johnson planing help

Is there a tag on it? What HP is the boat rated for?

If this little tidbit of data has any truth to it, it might be rated for 65?
Boat: 1972 Fabuglas Trident Fisherman 146

If yes, it's really asking a lot for a 35 to push it with any type of load whatsoever. As already suggested, you can try to go down in pitch and see how it does...that's about your only hope short of throwing gear overboard...
 
Last edited:

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: 35 johnson planing help

Looks like a prop is in order. The 11" is pretty far down the list .For heavier loads.
The 35 is good for 30 ish on a light reasonably fast boat.
A small glass boat might struggle with a load.Not a very big footprint to get a load up.
I would think a 10" would help and still get you some speed.
A 9" would surely solve your problem but may over rev with a light load and reduce top speed.
 
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