1970s Evinrude 4hp, wont run consistantly

The engine will fire if I put gas in the cylinders and on the spark plugs, but it wont keep it up, the gas tank and bubble are fine and working, I can hear the gas going into the carb, but I just cant keep it going, runs for about 10 seconds. What could the problem be?

Re: 1970s Evinrude 4hp, wont run consistantly

You might have a stuck carb float preventing the gas in the bowl to actually get into the motor...or you're getting too much fuel & flooding the motor.

When was the last time the motor ran well? Has the carb been degunked/rebuilt?

MAS

Re: 1970s Evinrude 4hp, wont run consistantly

I bought a 1971 4 HP last fall and it would troll fine but every 10 minutes or so it would stop running. One pull and off it would go for another few minutes. I rebuilt the carb. and it runs forever now without any problems. I would suggest a carb. kit. These are great little motors and so far have had no difficulty getting any kind of parts. I'm not sure what you mean when you say the bubble is working. Rick.

edit: If ordering a carb. kit get one that includes a new style float as the existing ones are cork and susceptible to damage from modern gas. (can't remember what it's called)

Re: 1970s Evinrude 4hp, wont run consistantly

Rick. said:

I'm not sure what you mean when you say the bubble is working. Rick.

Click to expand...

I was thinking he meant the fuel line bulb for an external tank??

MAS

Re: 1970s Evinrude 4hp, wont run consistantly

I'll bet your right, I just didn't think of that. Rick.

Re: 1970s Evinrude 4hp, wont run consistantly

agree with carb cleaning, and rebuild kit. then proper adjusting.

directions, but you 2 adjustable jets instead of fixed jets,
http://forums.iboats.com/showthread.php?t=244013


this is the proper kit for your motor. even though it say differently.
http://www.iboats.com/mall/partfind...&gd_poid=109333&gd_row=4&**********=395038034



(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle va /lve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Re: 1970s Evinrude 4hp, wont run consistantly

Its been a year or so since its been run, I think it might be the carb but I'm not sure how to go about cleaning it the right way without messing it up, does anyone have a step by step process, it seems like a simple motor.

Re: 1970s Evinrude 4hp, wont run consistantly

basic principles http://forums.iboats.com/showthread.php?t=244013

Re: 1970s Evinrude 4hp, wont run consistantly

No one has said it yet so hear goes. You simply must get an omc service manual for your specific motor. There are just too many things to rely on the forum for step by step instructions, many of which are in the manual. It will pay for itself in no time at all. I wrecked a 4 HP carb by trying to remove the choke plate screw. The manual says it is piened over at the factory to prevent it from falling out and being sucked into the motor. I had the manual on order at the time.......... but I hope you get my point. Rick.

Old evinrude 25 hp electric start 1970-1980 how to start?

Old evinrude 25 hp electric start 1970-1980 how to start?

Just got and old 25 hp electric start evinrude, early 80s late 70s I think, whats the best way to see if she runs?

Re: 1970s Evinrude 4hp, wont run consistantly

When changing topics use the "new post" button in the upper left of the main window...you'll get better results.

But to your question:

Spray some lube into the cylinder through the spark plug holes to coat the dry cylinder walls.

Install new plugs and gap correctly. Check for spark.

Check compression numbers, if low and/or uneven, do a decarb with seafoam...it might bring your numbers up.

Use fresh gas 50:1 oil mix

Change lower unit oil...if old lube oil is milky, you've got water intrusion. Make sure you use new "crush washers" on the drain and fill plugs.

Plan on changing the water pump and checking the thermostat after you get her running.

AMS