1976 Evinrude 70 HP

[Uncle Fred]

Here's another "loosing power" poblem.<br /><br />The boat was layed up from spring of '89 until<br />2001. The first time out with fresh 91 octane,<br />new gearcase oil and sparkplugs she ran just fine<br />on my Glastron V140 doing about 40 as she used to.<br />About an hour or so of changing fishing spots and<br />starting and stopping she came down off full power to about 5 to 7 mph. Another time or two<br />out last year got me less running time at full<br />power. This year I want to sell it so I took it<br />out and she flew for about 15 minutes. I began<br />with the pickup tube in the tank: Strainer = clean. Bought a new hose with bulb and plugs. Changed every rubber tube under the hood. Rebuilt<br />the fuel pump. Compression is 125 per cylinder. Took the 3 carbs apart and thoroughly cleaned them out and checked the floats and valves. Replaced the waterpump somewhere in there. Called the marina I bought it from in '78<br />and he said there was a re-call on the driveshaft<br />bearings. It siezes up enough to bog you right down. Something about it not getting the oil.<br />I took the lower unit apart and checked the bearings. Both are submersed in hypoid and in good condition. Being at wits end I swallowed my pride and took it to the local marina. Mechanic<br />said all it needed was a vented fuel cap. Said he had it out for almost a 1/2 hour at full power and<br />it ran great. Cost me $29 for a gas cap and $65 for labor. Took a potential buyer out last night and she took off like a bat outta hell. 2 minutes of that and she powered down. Lost the sale and blew my top!! Any help will be greatly appreciated. Thanx.<br /><br />Uncle Fred

 

[JB]

Re: 1976 Evinrude 70 HP

Howdy Uncle Fred.<br /><br />I suspect that you are losing spark on one cylinder after the ignition system gets hot. Cool it down and it works again. <br /><br />Crank it up on the ears and use a hair dryer to heat each part of the ignition system. If there is a heat failure there will be a slight drop in rpm at idle, and the last item you heated is probably bad.<br /><br />This test works much better if you can do it with the engine under load.<br /><br />Good luck.

 

[ND Boater]

Re: 1976 Evinrude 70 HP

Hello Uncle Fred,<br /><br />I have a 1977 75hp evinrude at it is having the same problem. It usually runs well for about 10-15 minutes and then it starts loosing power. Sometimes it comes off plane.<br /><br />JB, I have tried the hair dryer trick, but I just can't duplicate the problem unless I have it out on the lake running near full throttle. With the engine running in my driveway with the ears on I started check voltages in the powerpack. The A/C voltage between the two stator leads is only about 50 volts. My manual says that 300 volts A/C should be generated. Also the voltage between the primary coil ignition leads and ground in the powerpack are very low, less than a volt. They are steady, but doesn't this seam a little low?

 

[petryshyn]

Re: 1976 Evinrude 70 HP

ND boater<br />Best time to check these voltages is when you are having trouble. What are you using for test equipment? You must use a peak reading meter or a DVA adapter. A conventional voltmeter will read low....

 

[ND Boater]

Re: 1976 Evinrude 70 HP

I'm using a very cheap analog meter. Where can I get one of these DVA adapters or peak reading meter. I don't think I've ever seen one.<br /><br />Thanks,<br /><br />ND Boater

 

[rsl31652]

Re: 1976 Evinrude 70 HP

Firtst rule in diagnosis is to isolate the problem. Is it fuel, electriclal, neither, etc. 9 out of 10 times it will be the power pack (cd box) if its an electical problem. DVA's and peakreading Voltmeters are available thru Stevens Instruments. When the engine slows, use your choke, if it revs up your problem is fuel ( providing it is not a flooding problem. Cheap spark checkers from snap-on would be a wise investment for your diagnosis process. Have someone else drive the boat so you can watch the spark checkers.

 

[ND Boater]

Re: 1976 Evinrude 70 HP

Thanks Outboarder,<br /><br />I don't think it is a fuel problem because the problem is so intermittent. I have tried using the choke and pumping the bulb while having the problem with no success. If the problem is an ignition problem, it seems to be that being able to check the voltages from the timer base, the charging coils, and the ignition leads from the powerpack while the problem is occuring (which is only out on the lake) would tell me what is wrong right away. I just haven't quite figured out a good way to do that.<br /><br />Uncle Fred, sorry for taking over this post. It just sounds to me like we are having the same problem and I would love to find a solution.

 

[gessner17]

Re: 1976 Evinrude 70 HP

Was this ever solved? I'm having what seems to be the same issue with my 76 70HP Evinrude.