1976 70hp Evinrude ob

[camera guy]

I have a glastron 1976 156 trihull with a 70 hp Evinrude. It is always stored inside with a cover so it is in near mint condition. My Dad purchased it new. Until 2007, it started and worked perfectly (we don't live near a lake, so it gets used a couple time a year). In '07, it began lurching at planing speed. We brought it to a repair facility for Evinrudes. When we got it back, it started perfectly and idled -- as soon as we shifted, it stopped (only in the lake, in the drive-way it ran perfectly at all speeds). We returned it and some linkage was fixed (another $90) and it worked great in the drive-way and in the dealer's tank -- in the lake it started, idled at trolling speed for hours BUT when the throttle advanced it would run for 15 - 30 seconds and then act like it was running out of gas. I change gas tanks; gas hoses; ran with the cover off the tank; pumped the bulb when running with the same results. A 3 trip to the dealer -- same results (he has never lake tested, only tank tested). First time they put in a new carb kit, The 2econd time they installed new needle and seats (said old ones were stuck); don't know what they did the 3rd time. TWO things more, if I run just faster than trolling speed, then when I fully advance the throttle, it does NOT change speed; And after it starts to hesitate, if I go back to trolling speed for 3 - 5 minutes, I can again advance to full speed for the 15 - 30 seconds before it hesitates.

Help

 

[tashasdaddy]

Re: 1976 70hp Evinrude ob

sounds like you need the OEM service manual, and the motor need linc n sinc. by now probably needs carbs cleaned again. http://forums.iboats.com/showthread.php?t=299680

manuals http://www.outboardbooks.com/index.cfm?fuseaction=models.main&year=1976&ID=54493

 

[camera guy]

Re: 1976 70hp Evinrude ob

Can you explain the linc & sinc & is this something that an Evinrude dealer should have taken care of in 3 trips?

Also, what are the icons in the 'Quick Reply' that I am supposed to hit to activate the quick reply

 

[tashasdaddy]

Re: 1976 70hp Evinrude ob

yes, just hit quick reply. but this is a forum, not a chat room, so do not expect immediate response.

 

[camera guy]

Re: 1976 70hp Evinrude ob

please explain linc & sinc

 

[KDT1961]

Re: 1976 70hp Evinrude ob

linc & sync is making sure that your ignition timing is synchronized with your carburetors. Boat motors may work in the driveway and in a dealers tank because they are not under a load, and can run on 1 cylinder. When you put them under load (in the lake) they will bog down because they need all cylinders to work. Your motor may not be running on all cylinders.

Since your problems started in 2007, you may be experiencing the effects of Ethanol additives to your gas. If your fuel lines are original, they are not resistant to Ethanol and will deteriorate, clogging the jets in your carbs. That is one possibility. New alcohol resistant fuel lines, carb overhaul and linc & sync.

You have a 30+ year old motor and based on what I am finding out, not too many service centers really know how to work on these.
Your best alternative is get a service manual and work on it yourself, with suggestions and advice from here.

 

[camera guy]

Re: 1976 70hp Evinrude ob

linc & sync is making sure that your ignition timing is synchronized with your carburetors. Boat motors may work in the driveway and in a dealers tank because they are not under a load, and can run on 1 cylinder. When you put them under load (in the lake) they will bog down because they need all cylinders to work. Your motor may not be running on all cylinders.

Since your problems started in 2007, you may be experiencing the effects of Ethanol additives to your gas. If your fuel lines are original, they are not resistant to Ethanol and will deteriorate, clogging the jets in your carbs. That is one possibility. New alcohol resistant fuel lines, carb overhaul and linc & sync.

You have a 30+ year old motor and based on what I am finding out, not too many service centers really know how to work on these.
Your best alternative is get a service manual and work on it yourself, with suggestions and advice from here.

Thanks for the advice -- armed with your ideas I took it back for the 4th time. They tested under a load this time and were able to dublicate my symptoms. Checking and re-checking, they found the fuel line to the bottom carb had a slight pinch thus restricting fuel when the motor was operating under a load -- I'm sure going at trolling speed for a time allowed the carbs to fill up and thus run for 15 to 30 seconds before running on only 2 or 2 and a partial 3rd. The problem probably happened on the first fix when they put in a new line that was slightly long.

 

[SS140]

Re: 1976 70hp Evinrude ob

Im not brainiac but Im willing to bet you coulda figured that one out on your own buddy. I mean, how hard is it to miss a crimped fuel line? xD

Grats on getting it fixed.