1976 85 HP Johnson Seahorse - Engine issue

[guamster]

A couple of weeks ago I went to try to start the motor and it would not start. Engine turns freely and spark is blue. The oil/fuel mix ratio for this engine is 50-1. I recently purchased a cup that shows exactly how much oil to add to a 6 gallon tank. Approximately 16 ounces if my memory serves me correctly. After quite a few tries of attempting to start motor, I gave up but noticed that this same part of the exhaust housing pictured in this link was dripping what appeared to be excess oil along with fuel. After letting the boat sit for about a day, I went to try to start it and it fired right up. After letting it idle and warm up, my buddy and I decided to take it for a spin on one of the local lakes that we camp at. Everything was good until about 5 minutes into the ride. We were heading back in at WOT when the engine just died right in the middle of the lake. I tried starting again and no can do. Same behavior as day before. It is worth noting that the engine response when the engine is running is flawless. The motor runs and sounds like a formula 1 race car. After being towed in, I raised the motor and out came more oil and fuel. So my question is this. Is it possible that even at 50-1 these older motors were supposed to run a little lean...meaning less than 16 ounces per six gallons of gas? This boat came straight out of a time capsule. It literally is like new except that it pretty much sat in a garage since 1977. I'm thinking that it's a fuel issue. Should I try running with less than 16 ounces per 6 gallons? I suppose I could try and open the fuel filter housing and take a look at that.

Any ideas on what I should be looking for would be greatly appreciated. I would really like to have it on the water for July 4th weekend.

 

[emdsapmgr]

Re: 1976 85 HP Johnson Seahorse - Engine issue

An exceptional find. A real looker. Not likely the fuel pump quit all of a sudden, but it is possible. When it quits, try constantly priming the fuel hose bulb. This will force extra fuel into the carb bowls. If it is a bad pump, the constant priming will remedy that issue for your test run. More likely the ignition quit. Weak ignition components tend to fail when the engine warms up to normal operating temperature. Take an inductive timing light with you next time out. When the engine quits, put the timing light lead on each plug wire and see if you have spark. The flashes in the gun will tell you the quality of the spark on each wire. You might want to take a laser temp gun with you and check the head temps to make sure you are not overheating. Should be in the 140-150 range normally.

 

[Monte1961]

Re: 1976 85 HP Johnson Seahorse - Engine issue

50:1 is the correct fuel/oil ratio. (Better heavy oil than lean) Your on the right track. If the carb/s have not been overhauled, they need to be. Get OEM kit/s. Check floats for cork or heavy with fuel. Replace with new. Remove any and all core plugs. Remove high/low jets. Remove seat/s. Allow carb/s to soak for 24hrs.(NO PLASTIC OR NYLON). Rinse with fresh water and blowdry any ports, holes inside and out. Reassemble carb/s and provided by instructions. Do a link & sync. Note: If impeller hasn't been change within the last 2 years, I recommend it be change also. Good luck and post back.