1979 15hp Dies When Throttle Opened

[Jogerst]

Hello all,

I have a 1979 Evinrude 15hp that I have been in the process of restoring. I replaced the coils Sunday and it finally runs well. I ran it for about 20min today in a barrel before taking it to the lake and it started on first pull and ran flawlessly. When I got the lake though, it was a different story. It died when I put it in gear, did not start on first pull, and when I was able to keep it running when i switched into gear, it would die when I hit about half throttle. I began pumping the bulb while it ran and was able to go to WOT--but only while i continuously pumped the bulb.

What's wrong?

Thanks

 

[Daviet]

Re: 1979 15hp Dies When Throttle Opened

By pumping the primer bulb you are bypassing the fuel pump. You might want to check the fuel pump operation.

 

[Jogerst]

Re: 1979 15hp Dies When Throttle Opened

How to I check if it is working or not?

Also, the main fuel line in the motor is original and old. There are surface cracks on it, could it be possible that when the throttle is opened and the suction increases, air could be sucked in through an unseen crack?

 

[Daviet]

Re: 1979 15hp Dies When Throttle Opened

You should replace any cracked or damaged fuel lines.
Remove the fuel line on the pump that goes to the carb, pull the engine over and see if you get spirts of fuel out of the line.

 

[gonefishin485]

Re: 1979 15hp Dies When Throttle Opened

Sounds to me like bad fuel pump or carb float set wrong. A fuel pump that isn't pumping enough will do fine at an idle but when you put a load on it and the fuel starts dumping in the motor the weak pump can't keep up. Also a float out of adjustment will do crazy things. The float in the carb regulates the amount of fuel in the carb. Too much fuel in the carb, it might idle but would flood out from too much raw fuel bieng dumped in at one time. Too little fuel and it might have enough fuel going to the idle jet, but not enough to the main jet. From what it sounds, your issue is the latter. I'm not a certified mechanic, but this is how I set all my carb floats: take the carb off and remove the bottom bowl. Inside you'll see the float and riding on the float will be a needle that goes into a valve. As that float and needle raise the fuel supply gets lower and when the needle is all the way against the seat, the fuel supply is shut off. So I take my carbs with the bowl off and hold them upright so the float falls down then I slowly push the float up untill the needle stops moving. At that point the float should be parallel to the bottom of the carb surface where the bowl goes. If its not, just bend the little metal tab either way untill the needle is fully closed and the float is parallel to the bottom of the carb. Then give your motor a try. If that doesn't fix it, you might need to adjust your fuel air mix screw if you have one. I always start my base line testing by screwing the fuel air mix screw all the way in, untill it LIGHTLY bottoms out. Then unscrew it 1 and a half turns back out. You may have to go either way with the screw untill it runs right. These are both free things you can try at home to see if its either the float or mix screw. It neither of those make a difference, then I'd say fuel pump. Lastly make sure all your fuel connections are good and not sucking air from anywhere and make sure your primer bulb is in good shape. Usually something small like that can give you the blues.

 

[Jogerst]

Re: 1979 15hp Dies When Throttle Opened

You should replace any cracked or damaged fuel lines.
Remove the fuel line on the pump that goes to the carb, pull the engine over and see if you get spirts of fuel out of the line.

I will definitely check the fuel pump, thanks!

 

[Jogerst]

Re: 1979 15hp Dies When Throttle Opened

Sounds to me like bad fuel pump or carb float set wrong. A fuel pump that isn't pumping enough will do fine at an idle but when you put a load on it and the fuel starts dumping in the motor the weak pump can't keep up. Also a float out of adjustment will do crazy things. The float in the carb regulates the amount of fuel in the carb. Too much fuel in the carb, it might idle but would flood out from too much raw fuel bieng dumped in at one time. Too little fuel and it might have enough fuel going to the idle jet, but not enough to the main jet. From what it sounds, your issue is the latter. I'm not a certified mechanic, but this is how I set all my carb floats: take the carb off and remove the bottom bowl. Inside you'll see the float and riding on the float will be a needle that goes into a valve. As that float and needle raise the fuel supply gets lower and when the needle is all the way against the seat, the fuel supply is shut off. So I take my carbs with the bowl off and hold them upright so the float falls down then I slowly push the float up untill the needle stops moving. At that point the float should be parallel to the bottom of the carb surface where the bowl goes. If its not, just bend the little metal tab either way untill the needle is fully closed and the float is parallel to the bottom of the carb. Then give your motor a try. If that doesn't fix it, you might need to adjust your fuel air mix screw if you have one. I always start my base line testing by screwing the fuel air mix screw all the way in, untill it LIGHTLY bottoms out. Then unscrew it 1 and a half turns back out. You may have to go either way with the screw untill it runs right. These are both free things you can try at home to see if its either the float or mix screw. It neither of those make a difference, then I'd say fuel pump. Lastly make sure all your fuel connections are good and not sucking air from anywhere and make sure your primer bulb is in good shape. Usually something small like that can give you the blues.

Thank you for all the possible trouble shooting! I had my carb rebuilt last November and I even took it back to have them fine tune it. It runs really well in gear in a barrel or with ear muffs, but just not today on the water. I am hesitant to pull the carb because though I am relatively mechanical, I may not be that mechanical!

Any reason it would not start first pull when I was on the water? Maybe over primed the bulb and flooded for a bit?

 

[gonefishin485]

Re: 1979 15hp Dies When Throttle Opened

Its a definite possibility that you might have flooded it, every motor is different. like with my 1986 50 merc, I have to damn near flood it and have raw fuel fuel dripping out the carb over flows to start it, while my 1977 johnson 85 I only pump it untill the bulb feels full, not rock hard, just full or else it will flood and run down a battery trying to start it. Next time you try it, try pumping the bulb just enough untill it feels full and you don't hear any more air escaping from the carb. Then let the fuel pump do its job and see how well it pumps and picks up fuel. I'm pretty confident that your problem is something minor. The biggest headaches usually are something minor. If your carb is good, then to me it sounds like a fuel delivery issue. Perhaps in the fuel pump or even in the primer bulb. I'm no scientist but this is how I see it, If your pumping the bulb with your hand, then your the fuel pump. If you stop pumping and it bogs down, or dies, then your internal fuel pump is gone. Might even try cleaning the spark plugs. Years ago I had a two stroke dirt bike that would idle and rev great with no load on it, but as soon as the motor had a load on it, it wouldn't run worth crap. Thats how I knew it was time to clean or change the plug. Let us know how you make out.

 

[Jogerst]

Re: 1979 15hp Dies When Throttle Opened

I took the boat out three times over the weekend, and each time she fired right up on the first pull. I noticed that it only takes a few pumps of the bulb and there is plenty of gas to start it, so I guess I was in fact flooding it before. I also ran at WOT across the lake numerous times and actually hit 23mph by myself (1436 Tracker) and she ran very smoothly. I did however have to continuously pump the bulb, but only every 10-15 seconds. Annoying but I can live with it until I am ready to fix the fuel pump. So in the end, it is the pump that is bad. I have yet to pull the fuel hose and check the actual function of the pump because of lack of time, but it seems to be the problem. I also did a decarb using Sea Foam and she runs better than ever.

Thank you to everyone for their input, it was greatly appreciated and very helpful!

 

[Jogerst]

Re: 1979 15hp Dies When Throttle Opened

One final question though...

When I do replace the fuel pump, is just a new gasket needed? Or the entire fuel pump assembly? If neither, could someone let me know the parts needed?

Thanks!

 

[Daviet]

Re: 1979 15hp Dies When Throttle Opened

Below is a breakdown of your pump. You will need #1 pump and #7 gasket. I think sierra might make a kit to rebuild your old pump, you will have to search it out.
:: iShopMarine.com ::

 

[raczekp1]

Re: 1979 15hp Dies When Throttle Opened

i instaled sierra kit and pump run well

 

[OptsyEagle]

Re: 1979 15hp Dies When Throttle Opened

Also, your problem may not end up being a bad fuel pump. Your problem is in the pumping of fuel, but that can be stopped by an unvented fuel tank, a faulty fuel hose, an air leak on any connection, a stuck float or inlet needle on your carb and of course a bad fuel pump.

Before I would rebuild the fuel pump (a very delicate operation) I would run it with the fuel cap off to verify that the issue is not a venting problem. If you can, try another fuel hose to eliminate that item. Look for any possible loose hose clamps or quick connectors. Verify that all four screws on the fuel pump are very snug. If none of those fix the problem, then disconnect the fuel hose to the carb and pull the starter rope. If fuel does not pump out, then rebuild the fuel pump, if it does, fix the inlet needle/float problem that is happening in your carburetor.

 

[Jogerst]

Re: 1979 15hp Dies When Throttle Opened

I was hoping I wouldn't need the full assembly, oh well. And before ordering anything, I will definitely make sure it is the fuel pump and not any air leaks, no use in wasting money on something I don't need. As for the carb; the bulb hardens and the carb does not accept fuel at a certain point--meaning the float has risen to its highest point, correct? That being said, could it possibly still be the float? After having two people mention the carb, it has me wondering.

Thanks