1958 18hp johnson seahorse

I have a 1958 18hp johmson seahorse. It is a pressure tank system. I got it home and tried it and it starts and runs breifly and dies. If you pump the bulb on the tank it will stay running? I have spark and the tank hold pressure i dont know what else to do. It seems like the tank is not getting prussurized by the motor

Re: 1958 18hp johnson seahorse

Hi J. Welcome to iboats. Great old motor you got there. I love the reverse two tone paint job. Have you cleaned/rebuilt the carb since you got the motor? If not, you probably should. It's not a hard job and you can get a rebuild kit right here at iboats for about $20. See the how-to links below. You should probably inspect all the fittings in the fuel lines to see if there are any leaks too. A bit of spoapy water will do the trick. Thankfully, these old motors really only need 3 things to run; Spark (should jump 1/4" gap on each cylinder), Compression (anything over 80 psi with the cylinders within 10% of each other is good), Fuel (24:1 mix which is about 5.5 fl. oz. to 1 US gallon of 87 octane gas).

http://www.marineengine.com/parts/v...ntage-evinrude-johnson/377515/37751500001.htm

http://www.leeroysramblings.com/johnson_E-FD_15_18hp.html

http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

Re: 1958 18hp johnson seahorse

Could it possibly be a bad reed valve? I am goint to try to rebuild the carb that diagram seems pretty explanatory

Re: 1958 18hp johnson seahorse

It's very rare that there is a problem with the reeds. It's almost always the carb and/or fuel delivery system such as the fuel pump, or in your case the pressure tank. A carb rebuild is never a bad idea and it's the cheapest/easiest thing to check. Be sure you're using Champion J4C, or J6C (if you do lots of low speed tolling) too. Here's another handy carb link. It's for a different model, but all the steps are the same.

http://www.outboard-boat-motor-repa...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm

Re: 1958 18hp johnson seahorse

You say if you pump the bulb it will stay running? Is this a single line tank? If so, the motor has a fuel pump, and it is not a pressurized tank. A pressure tank has two lines and a button on the tank to prime the motor. No inline bulb.

Re: 1958 18hp johnson seahorse

yes it is a two line system

Re: 1958 18hp johnson seahorse

When you unscrew the cap on the tank, does it make a "whooshing" sound indicating it is pressurized? Pumping the button does not pressurize the tank - it only pumps gas into the carb to initially start the motor. The running motor is what pressurizes the tank, and that pressure pushes gas out of the tank to the carb. If the tank isn't pressurizing after the motor has run a few minutes, you have an air leak in the system, or a bad tank gasket or diaphragm.

Re: 1958 18hp johnson seahorse

You can convert the motor to a modern, single line set up if you like. It's pretty easy, will streamline the fuel system and allow you to use modern fittings and tanks. I'd still start by cleaning and rebuilding the carb, but here are some links if you're interested in the conversion.

http://www.leeroysramblings.com/Converting_dual_fuel_line.htm

http://www.youtube.com/watch?v=FtG4M7ye1N8&feature=related