50 HPJohnson help

We had the Johnson 50HP (1999,2000, or 2001 model) on the pontoon, started this year acting up for Dad at the camp ground my parents are staying at. The motor will run great for an hour or so, then starts acting like your letting off the gas then getting back on it, Kinda like revving the engine in a car then dies. It will run a low throttle. Well when I took it out to investigate, it was starving for fuel. the supply line bulb is collapsed. I figured the lining had collapsed, or they was a check valve sticking or they was trash in the permanent tank. No hurry to fix it, Dad only drives it 5 mins to his honey hole. Oh it has a oil tank so you don't have to mix the gas.

We pulled it home, dad decides he wants switch motors. So I swapped the 50HP over the my Lowes, and put the 35 Merc on the pontoon till we can figure out what 4 stroke brand to get. (any ideals it's rated for up to 130hp, but thinking something with good gas mileage?)

Well took it out today, did the same thing. Different tank, new fuel line, tank of fresh 100% gas bought Friday. Primer bulb on the line was half flat, compressed and stayed that way when I squeezed it.

My 1st thought was it was the power pack or it was over heating, but that wouldn't make the bulb go flat. I opened the gas cap to see if maybe the tank cap vent was plugged. Once it dies the bulb refills, and it's runs good for at least 30 Mins (how long it took me to get back the truck). I thinking maybe we have similar problems on both boats, and it just a coincident that cause the motor to have the same problem on 2 different boats and fuel system. I can't remember the brand of tank, but would an aftermarket tank have screen or something in the tank? Can anyone think of any thing motor related that would cause this?


While I'm asking for help. I could only get it to about 20mph per the gps, at about 5k rpm, and it wouldn't ever get on plane all the way. I'm guessing it prop related. Any know what pitch I need? Or I'm thinking wrong and I need to adjust the motor placement someway?

Thank you in advance,
James

have you made sure that BOTH tanks have their vents open? a tank starving for air will collapse the bulb and stall or slow down the engine.

Look into the new Tohatsu four stoke 50.

Check the vents for the tanks and if your fuel line is not ethanol rated swap both boats fuel lines out. The line may be collapsing internally on both boats. May want to check any fuel filters and fuel pump. I had to replace anything fuel touched on my outboard due to the ethanol fuel. Go back with ethanol approved parts. Almost all gas no matter how it is advertised has some sort ethanol in it.

I opened the cap, thinking that was it. Brand new fuel line from Wal-Mart. Dad wanted a portable tank in case he didn't want to pull the pontoon out to get gas. So I gave him the mercury fuel line.

Maybe ethanol did something to the tank?

What happened when you took cap off tank? Was bulb collapsed when you opened the tank.? The only thing that will make the bulb collapse is a restriction between bulb and tank or tank not venting properly. Take the fuel line loose at the motor, cut the connector off, get you a gas can, put the can below the fuel tank, put open hose end in can and slowly pump bulb and see if you get a good stream of gas with cap on tank. Then pump and hold the bulb, place your thumb over the open end of hose, release bulb. If everything is as it should be the bulb should expand pulling gas from tank to fill bulb. If it does not still holding thumb on hose crack fill cap on tank. If that doesnt work you have a restriction in the connector to the tank or in hose. The pickup tube in your tank should have a screen on the end to keep trash out.
How big a Lowe boat you put it on? Bet the prop is for the pontoon and to small in pitch for your boat. Would think 2 sizes bigger but hard to tell without knowing what you have now, how big your boat is and where it's mounted on transom, aluminum or stainless and does it have trim and tilt.
On 4 stroke, get in touch with BigRiverMarine on here. He is a board sponsor and will give you about as good a deal as you can find anywhere and probably make it worth the drive to Memphis for it. I would opt for the Tohatsu but he is a Yanaha dealer and can get you either one.

Didn't do anything different with or without the cap.

Ya it's the prop for pontoon, figured I'd need to change it to get top speed, but got to thinking maybe I had more problems. Guess just wasn't getting enough speed.

It's on I think a 16ft, I'll double check. I mounted with the motor catch tab on top transom. Aluminum prop. It's got tilt and trim, but I had it all the way down and bow still was pointed up.

Then you have a restriction somewhere in that line. You said it's new, is it the same line you were using on the toon? Make sure arrow on bulb is pointed toward motor. I have never had any luck with hoses from Walmart. Get your old Merc hose and change motor end and try it.
Yep your not getting enough speed to lift the transom to get it on plane. Aluminum prop should be ok all the way down. Get boat level and trim motor where it is straight up and down. Cavitation plate should be just below or even with bottom of boat if you ran a straight edge between the two.

It was different fuel lines. I got around to looking at the model, Lowes 16B catcher pro.

Well I worked on it some, hooked up a spare tank fitting I have for the tank I haven't got around to buying yet. The primer bulb flowed like I'd expect normal is. I took the hose with screen fitting out of the tank, didn't seen any gum or goo on it. Was a lot of trash in the tank, that I guess could collected on the screen over time, then fell off when motor quit sucking. I emptied the tank and then wiped it out with a rag on a rod, got 99% of it out. (still was a couple flakes left). I'm planing on taking both hoses next Friday, feed the old one out a gas can. But hoping out was the junk in the tank.

Dad talked to mechanic who used to work on his boat motors today at church. He thought it was probably either a weak fuel pump or an air leak in one of the fuel lines, but well not sure how well Dad and him communicated. He suggested to dad that we start with changing the fuel lines. sounded like a good ideal considering they are almost 15 years old, and I replaced a oil line that had split last year when it overheated. So far I've changed out the bigger lines, but will have to buy the smaller lines. Need to get a new fuel filter too. I don't see how this could cause my problem, but like I say pretty safe Ideal anyway.

It has another problem, the electric primer/choke thing don't work. You have to turn the manual knob thing on the side of the motor to start it cold. I finally got around checking on it, it gets power, So I got to replace it. Any one ever done it? Any surprises I should expect if I do it my self?

You may have discovered the problem when you found leaves in the tank. They will clog up and inlet filter pretty quick and would cause the bulb to go flat. If you can't get them out might need to get a new tank. I would also clean the fuel screen on the fuel pump.

More like dead algae than leaves. Between cleaning the junk out of tank, replacing all fuel lines but the 5/32 ones and the fuel filter; it runs good.
Put a fin set up on motor and it gets on plane. Still only does 21 at to speed, but the ride is better.

Thank you all for the help and support