Johnson 1957 7.5 HP AD-11 Fuel Starved!!

[marcb]

Hi all,<br /><br />My 1st post. I just purchased a 1957 Johnson Sea Horse 7.5 HP, Model AD-11. We got it started just fine, but when we splashed it and put it in gear, it barely made headway speed. I noticed quite a bit of fuel leaking out of the coupling; it appeared that there was a blockage preventing adequate fuel from getting to the motor. I looked at the male (engine mounted) connectors and could not see a passage hole. They almost looked solid. I poked at them gently with a scratch awl, but still could not see a passage. A lot of pressure also built up in the fuel tank, which I relieved periodically. I tried every possible combination of rich/lean mix and fuel tank pressure, but could not get the thing up to speed. I had a couple of very brief moments when the engine started to pick up speed, but then it immediately died.<br /><br />Do I need to replace something, ordo I have a blockage? Any help would be greatly appreciated; I'm a bit of a novice when it comes to outboard engines, especially old ones.<br /><br />Thanks-

 

[PDS]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

Hi, Marc! While I'm not familiar with that motor, I know you need to fix that fuel leak. Usually a worn out o-ring. And unless that motor has a fuel pump(I really don't know) it uses built up pressure in the fuel tank to push the fuel up to the carburator. With a manual to assist you, I'd take the carb. off and rebuild it and look for any blockage in the carb. For that you have to take carb. apart and clean it very well. Just how much do you know of this motors background? It's probably due a new water pump. Good Luck!

 

[Chinewalker]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

Hi Mark,<br /> A couple of things...<br /> First - it sounds like your motor is only running on one cylinder - with occasional fits of running on two. I'd be willing to bet that if you were to remove one of the plug wires while running that absolutely nothing will happen - or the motor will shut off completely. Take a peak at the coils under the flywheel for evidence of cracking. Make sure points are gapped at .020". If the condensers have the fiber caps, replace them with new rubber-capped condensers.<br /> Second - the fuel tanks is SUPPOSED to build up pressure. That's what drives the fuel into the motor. Relieving it periodically is not a good idea. Do take care of the leaky o-rings on the connector as they can contribute to a balky motor - not to mention the fire hazard. If the motor is getting fuel and the tank is pressurizing, then the male connector is fine. Concentrate on the female connector...<br /> Third - I hope you're running it on a rich diet of oil in the mix - preferably 24:1. <br /><br />- Scott

 

[dreambuilderstexas]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

I also just bought two 1957 7.5 HP johnson motors (yesterday) and started the first one this morning (the second is missing the rope other than that it is complete). The one I started today also had some of the same issues. I used to have a 1956 7.5 hp motor a long time ago (20 years) and I think the other gentleman is right. The tank and fuel system has to hold pressure. Any leaks should be corrected. Of course, lots of things can contribute to the engine running slowly. The need for a carburator overhaul (kit), simple adjustments to the carborators, spark plug wires, dirty plugs, burned or coroded points, water or trash in the fuel bowls, etc. Any combination of these can cause this affect. I reccomend getting a service manual. I just ordered mine off the web (about $37.00 incl shipping).

Did someone say we should run 24:1 oil mixture? I don't remember needing that much oil. I thought the mixture should be 8 oz of oil in 6 gallons of fresh gas. I think that is 50:1 isn't it? Is that right? Please correct me so I don't ruin my new (old) motors.

 

[samo_ott]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

a '57 is 24:1. Up till '64. Then 50:1.

 

[dreambuilderstexas]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

Thanks for the fuel mixture info.

I just bought these 2 Johnson 7.5 HP (1957) motors and the guy did noyt have the titles. He says one was from outside of Texas and the othet one he bought in Texas but neither had a title. Any chance anyone knows how to find out if the 2 motors I just bought have been titled before?

 

[tx1961whaler]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

Texas was not a motor title state until recently. You do not need them for those old engines, but repeat after me: "Officer, these motors have been in my family since 1957.......". The boat needs a title.

 

[GUINNESS!!!]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

Hi all. I was just helping my friend get his 1957 - JOHNSON - AD11 up and going. The gas tank for that needs to build pressure so it can deliver the fuel.
It has no fuel pump only an air pump that is why you have the 2 lines to the tank. One is the air return from the engine. Btw if you ever need to buy one they are not cheep. If you can find them they usually go for $100 or more. Just the 3 way fittings are as much as $45. You also need to prime the engine by pressing the little black button on the tank. Here is a little background info on them http://rides.webshots.com/photo/2810907050091848696mjfsNW

 

[marty 101]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

ive just recently found out about this site and i noticed you said 24 to 1. ive been running 5 ozs to 2 gals in my 57 7.5 does that seem to be enough or not would like an input

 

[samo_ott]

Re: Johnson 1957 7.5 HP AD-11 Fuel Starved!!

ive just recently found out about this site and i noticed you said 24 to 1. ive been running 5 ozs to 2 gals in my 57 7.5 does that seem to be enough or not would like an input

Welcome to the iboats forum.

Dunno if you're in Canada or the US but will assume the US. A US gallon is 128 oz. 2 gallons is 256 oz. Thus 5 oz to 256 is around 50:1 which is too high a ratio for an AD. I would double it to 10oz for 2 gallons.