1973 johnson 50 horse

[germo1983]

i have an 73 johnson 50 horse i need some info on the low speed needle adjustment. my motor will only run good at half turn out from closed on both carbs. it smokes good but whould like to know what factory setting is

 

[F_R]

Re: 1973 johnson 50 horse

There is no such thing as a "factory setting". 1/2 turn sounds reasonable. You set them to where it idles the best, then forget them. It is supposed to smoke. If you don't like the smoke, use 100% synthetic TC-W3 certified outboard oil, it will smoke much less.

 

[germo1983]

Re: 1973 johnson 50 horse

thanks for the info. i know it's sapost to smoke. i have another question. the prop on the motor is 13.750x15 pitch. the boat is an 1965 mfg niagara custom it will only go about 30 trimed out. my local prop shop says to go with an 12.250x21 pitch .i think that is to much of an pitch foe an 50 to push a old heavy boat.i would like to hit around 35-40. have a thought on what size to go with. i was thinking an 12.250x 17 or 19 pitch.

 

[F_R]

Re: 1973 johnson 50 horse

Don't try to second guess. You must have a tachometer to make any intelligent decision. I agree that 21" is probably too much, but that is not an intelligent decision, just a supposition. We'd all like to go 40 but......

Compare your prop to a car with stick shift. A flat prop is low gear, motor runs like crazy and will pull a stump, but won't go very fast. A steep pitch is like overdrive. Motor loafs along at 70mph, but won't go up any grade steeper than an anthill. Everything in between is a tradeoff. Remember in this analogy, with a boat it is always all uphill.

 

[germo1983]

Re: 1973 johnson 50 horse

the motor runs just shy of 6000 rpm at wot. i just replaced the gas tank with an plastic 6 gallon. my motor will run great out of the water, but when i put it in the water i seems like it runs out of fuel. the primer bulb is empty. and when i unhook the line, fuel sprays out with pressure at the fitting. never had that problem with the other tank.have any suggestions. the old tank was in the middle of the boat with a long fuel line on it.

 

[tashasdaddy]

Re: 1973 johnson 50 horse

open the vent on the gas tank, can't suck gas out of a vaccuum. 6000 is in the water i hope. if you are turning that on muffs, look out for a connecting rod to hit you in the face. i run 11 3/4 x 17 and 12x1/4 x15 on my 50hp and 40 hp, swap them back and forth, depending on what load i have in the boat. better holes shot with the 12 1/4 x 15. more speed with the 11/34 x17. i get a 5mph difference in the 2 props with just me in the boat.

 

[germo1983]

Re: 1973 johnson 50 horse

the vent is open on the tank. it seems like it runs bad only when the is pressure on the motor. runs like new out of the water. checked the commpression. it's at 155 psi in both cylinders. driand flaot bowls hoping i would see something come out. checked fuel filter it's clean. maybe there was a reason the guy i bouht the boat from had 6 feet of fuel line from the tank to the motor.like i siad it ran good with the old metal tank and the 6 feet of fuel line.

 

[tashasdaddy]

Re: 1973 johnson 50 horse

are you sure the new line is connected properly, there is an arrow on the bulb, the arrow point toward the motor. i've made that mistake before. the check valve won't let the fuel pump pull fuel from the tank.

 

[germo1983]

Re: 1973 johnson 50 horse

there is no fuel pump on the motor. the arrow is pionting torward the motor

 

[tashasdaddy]

Re: 1973 johnson 50 horse

if there is no fuel pump no wonder it won't run. follow the fuel line from the connector you will find a fuel pump. looking similar to this the black center is the fuel filter, could be clogged, remove the center screw and clean the screen, careful of the little seal around the outside. or it will have to be replaced.

http://www.iboats.com/Sierra_18_735...7 13655--**********.082699558--view_id.174141

with that statement i think you better get an OEM manual from outboardbooks.com

 

[jack361@centurytel.net]

Re: 1973 johnson 50 horse

side question why can i not acess this web site
outboardbooks.com
says not auttorized

 

[germo1983]

Re: 1973 johnson 50 horse

the block behind the filter. there are no wires going to the pump. doesnt a pump need power to it to pump the gas.

 

[freddyray21]

Re: 1973 johnson 50 horse

it's a diaphragm pump. gets a pulse of air from the motor to move a diaphragm and pump fuel. It's not electric. maybe get a manual for it.

 

[freddyray21]

Re: 1973 johnson 50 horse

btw I doubt you will ever see 40 mph out of that motor and boat. That is a lot of boat for a 50 hp to push 40 mph

 

[germo1983]

Re: 1973 johnson 50 horse

i ordered a manual from here today. i should get a 5 to6 mph increase in speed going to a 12.250x19 prop. it goes 30 at 6000 rpm with a 13.750x15 pitch prop.that should put me close to the speed i want.

 

[freddyray21]

Re: 1973 johnson 50 horse

you might find with a 19 pitch you have no hole shot

 

[germo1983]

Re: 1973 johnson 50 horse

i thought of that but it takes the boat a while to plane out allreadey. it should be about the same though. the new prop is smaller and lighter. than aluminum.