Help!!! 1977 75hp Evinrude

[New ND Boater]

I just bought a 1974 15' Lund with a 1977 75hp Evinrude. I have taken the boat out three times this year and each time I have a loss of power after running it pretty hard for about an hour.<br /><br />It's real weird because it runs great and then just loses power to the point where the boat won't plane. I can't believe that the carbs are plugged if it runs good for an hour and then has problems. I'm thinking electrical. Could something be getting hot. As far as I can tell from my service manual the temperature switch doesn't connect into the electrical system. It just activates a horn.<br /><br />All plugs seem to be firing. I've disconnected one at a time and let the engine idle and I can definitely tell a difference.<br /><br />Compression is 110,115,115.<br /><br />Why does this happen after an hour of running good?!!!

 

[JB]

Re: Help!!! 1977 75hp Evinrude

Howdy, ND. How long does it go at reduced power before you can get it to open up again?? Or - - do you have to shut it off and wait. . . how long??. . .before it will open up again??<br /><br />It sounds heat related, but could be from a vacuum build up in an unvented fuel tank.<br /><br />How strong and how warm is the telltale stream?<br /><br />What happens if you pump the primer bulb?<br /><br />Standing by.<br />JB

 

[New ND Boater]

Re: Help!!! 1977 75hp Evinrude

The one time I did stay on the lake long enough for the boat to act normal again it was about half an hour of idling and sitting with the motor off. After this the problem was intermittent<br /><br />Water does spit out of the tell tale holes, but it's not a lot unless I have the engine reved up. The water and exhaust that do come out of the tell tale are warm, but not hot. The mechanic I took the boat to said that on this engine I won't get a steady stream, just a little spitting. I have waited for about 20 minutes once with the engine off and this did not seem to solve the problem. I can touch the engine for about 3 seconds which is the same whether the engine is running good or having problems.<br /><br />Also, I have tried pumping the fuel bulb, and it makes no difference. I also made sure the tank was vented.

 

[Dhadley]

Re: Help!!! 1977 75hp Evinrude

Look under the flywheel at the stator and see if it appears the charge coils are "oozing". There will be what looks like melted plastic under one or all of them. If so then replace the stator. Even if this is not the cause it should be replaced if it's leaking. Your tech has the equipment to test it but you need to get it to the point where it's not running right and then test the system.<br /><br />Good luck!

 

[JB]

Re: Help!!! 1977 75hp Evinrude

'mornin' ND. From what you tell me I am inclined to think something in your ignition system is failing when warm, though the engine has not overheated. That is dropping a cylinder.<br /><br />Try pulling plug wires when it is misbehaving and see if there is one that makes no spark. That would confirm what you suspected from the beginnning.<br /><br />To isolate the cause, I want you to try a computer tech trick. Fire her up on the ears in the drive. Use a hair dryer (or hot air gun, if you have one) to heat up the ignition components associated with the misbehaving plug, one at a time, until one of them causes the plug to stop firing. Replace that component and you should be back in business.<br /><br />The above assumes that my suspicion is correct. If it isn't, tell us what happened and we'll go from there. Actually, tell us what happened either way.<br /><br />Red sky at night. . . <br />JB

 

[Liam]

Re: Help!!! 1977 75hp Evinrude

I recently had the same problem. Changed plugs, wires, fuel system etc. Ended up being the power pack! Hasn't had a problem since. I really like the hairdryre trick Ingenious!! and cheap to try .<br /><br />Good Luck and let us know.<br /><br />Liam

 

[New ND Boater]

Re: Help!!! 1977 75hp Evinrude

I may have figured out the problem, but here is a little history. When I bought the boat one of the ignition coils was cracked. I ran the boat twice and lost power after about an hour. I changed the coil and then took the boat out last night. Again after about an hour the boat lost power, but it didn't sound like it was dropping a cylinder this time, it just wouldn't go.<br /><br />J.B., after reading your post I decided to check the air valve on the tank. I was sure I opened it, but when I checked it this morning it closed. I opened it and heard a hiss. I'm a little upset I didn't check this last night, but I'm a rookie. On previous outings I did check the valve. <br /><br />I'm taking the boat out again this weekend and I'll let everyone know what happen. Thanks for all the ideas.

 

[New ND Boater]

Re: Help!!! 1977 75hp Evinrude

I got the boat out today and this time the engine had very little power to start with. The tank was vented so I guess that wasn't the problem. I did pull the spark plug wires while having the problem and they were snaping against the block.<br /><br />I pulled the carbs apart tonight and didn't notice any varnish what so ever, but I did notice that the gasket between the two haves of the air silencer and the gasket between the carbs and the air silencer were both missing. I don't know how important they are, but they aren't there.<br /><br />I will try the hair dryer trick tomorrow.

 

[New ND Boater]

Re: Help!!! 1977 75hp Evinrude

I tried the hairdryer trick with no luck. I took the boat out again today and ran well for about 15 minutes and then it lost power. I pulled each spark plug one at a time and they were all firing. I plugged all three back in and it ran fine for another 30 minutes until I took it in.<br /><br />Liam, you mentioned that it might be the power pack. There is no sign of cracking or melting on the powerpack. I suppose this could be the problem, but how common is it for powerpacks to go bad? Is there a simple way to check the powerpack?<br /><br />I can't get the flywheel off so unless there is a good way to check the components under the flywheel without removing it, I'm probably stuck taking it back to a mechanic.

 

[ND Boater]

Re: Help!!! 1977 75hp Evinrude

After asking for help I was sent to Kuwait so I never had the chance to completely solve this problem. When I returned in December the lakes in North Dakota were of course frozen. So, I haven't had a chance to do any testing until now. I appreciate all the help, but I did take it to a mechanic because I didn't want to spend all summer tinkering with the motor.<br /><br />He found that two of the three ignition coils had infinite resistance. I had checked the coils prior to taking it in, but I failed to see the little K between the 1 and Ohm on my cheap little ohm meter. What I thought was about 1500 ohms was 1.5 million ohms. Anyhow, I should get my boat back this week. If the weather heats up a little I'll test it and post the results. By the way, the stator looked good and the resistances check with the manual.<br /><br />The one coil that was good was one that I replaced because it had a crack. Does anyone know what would cause all three coils to go bad?<br /><br />Thanks