'76 Evinrude only runs with choke. Help?

[lahiggs]

I picked up a 76 MFG boat from a guy for a little bit of nothing. it has a 76 evinrude 75hp motor. the motor only runs with choke and will only go about 5mph in the water. any ideas with what could be wrong? i dont want to waste alot of money just to find out the motor is junk. but it seems to me it has to do with fuel, but i am no boat mechanic. any help would be greatly appreciated.

 

[Chinewalker]

Re: '76 Evinrude only runs with choke. Help?

Choke only operation generally points to gummed up carburetors. Rebuild all three carbs, paying special attention to cleaning the small jets and passages. Get a manual before attempting this project!<br /><br />It's also a good idea to run a compression check, as this can tell a lot about the motor - like if it was run for awhile with one of the carbs gummed up, which can lead to a lean condition and scorched cylinder.<br /><br />Also, consider installing a new waterpump impeller, unless the previous owner can document that it has been done in the last year or so.<br /><br />- Scott

 

[BF]

Re: '76 Evinrude only runs with choke. Help?

As CW says, it does sound like a carb problem. But start with the compression test. That'll tell you whether you'd be wasting your time and $$$ chasing down the carb problem. If a piston/rings/cylinder is toast then you've got much bigger problems. If compression on all cylinders is good, ~100+ psi and even across them, then do a happy dance because maybe you'll get it running good with a carb rebuild (cheap). Alternatively could be a fuel pump I guess... like I said worry about the compression before the fuel problem.<br /><br />Brent

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

Originally posted by Chinewalker:<br /> Choke only operation generally points to gummed up carburetors. Rebuild all three carbs, paying special attention to cleaning the small jets and passages. Get a manual before attempting this project!<br /><br />It's also a good idea to run a compression check, as this can tell a lot about the motor - like if it was run for awhile with one of the carbs gummed up, which can lead to a lean condition and scorched cylinder.<br /><br />Also, consider installing a new waterpump impeller, unless the previous owner can document that it has been done in the last year or so.<br /><br />- Scott

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

When I had in the water Sunday it ran only about 5mph at full throttle with the choke on. If I got it to run with the choke off, would it go any faster? I figure the 75hp motor should move that boat along pretty good. When I start in the driveway, it runs with no choke, just not in the river. Any ideas?

 

[Xcusme]

Re: '76 Evinrude only runs with choke. Help?

"Would it go any faster??" I would certainly hope so! Unless you're trying to push a barge. All kidding aside, the answer is yes, it will run better. Running the motor in the driveway on muffs, you have no back pressure as you do on the lake. Chinewalker has good advice, do the compression test, rebuild the carbs and go from there. Post back with your findings as it helps fellow boaters.

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

I will do that...I appreciate all the help. I am new to servicing boat motors, just don't want to go about it the wrong way. I'll post my results ASAP.

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

If the compression is below 100 psi, would the motor be worth rebuilding? or would it be cheaper to find a used motor?

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

I did a compression check and it was as follows from top to bottom:<br /><br />1- 150psi<br />2- 145psi<br />3- 150psi<br /> I guess I'm going to clean the carbs and see what happens.

 

[DJ]

Re: '76 Evinrude only runs with choke. Help?

The engine is healthy.<br /><br />The carburetors need immediate attention.

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

Where is a good site to buy a fuel pump?

 

[BF]

Re: '76 Evinrude only runs with choke. Help?

Hi again,<br /><br />That's good news on the compression! If the fuel pump is bad, you can usually tell by pumping the primer bulb while it's running poorly... if the motor picks up, then it's likely a bad fuel pump ('cause your hand becomes the fuel pump). As has been said, it does sound just like gummed up carbs. That's where I'd start. By the way, if you want to keep from damaging your engine you probably don't want to be running it much until you get this figured out. If the carb's are gummed, they're not giving enough fuel/oil... that means it's not getting much lubrication, and also running way lean (=hot). That's why you needed to check the compression, to see if had already been damaged. Lucky for you, it's OK.<br /><br />Instead of running it on muffs, it's better if you can put the lower unit in a barrel or garbage can filled with water. That'll give it normal backpressure on the exhaust (from the water) and you'll be able to see how it really idles once you do the carbs.<br /><br />Good luck.<br /><br />Brent

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

Thanks...I have took 2 of the 3 carbs apart and soaked them, working on the third now. I went ahead and picked up all new fuel lines and a new tank to motor line and bulb. I'll try running it in a barrel and see what happens. This BB is great..I'm glad I found it.

 

[lahiggs]

Re: '76 Evinrude only runs with choke. Help?

When I was taking the carbs apart I found a screw that I have no idea what it does. Its on the front of the carb on top, any ideas what this screw does? I took it out and I cannot see what it is supposed to do?