Motor Help

[Creede]

Early 80s evinrude 40

Runs great with muffs but won't run at the lake?

Starts fine but dies when turned down to an idle.

Motor sat for a season but I have gone through the carbs and cleaned them up and checked for problems there.

Should I start with Turning the throttle up with the motor in water or look into other potential problems?

Thanks for any advise

[fishinwrench]

Usually a complete synchronization of all of the control linkage will make a HUGE improvement.

Simply cranking up the idle speed stop screw might "keep it running" but to fix it proper there are 5 steps to syncing the control linkage that come BEFORE you ever touch the idle stop screw or the cable barrels.

That 40 also has a tuned exhaust and depending on the model will have either

1 or 2 seals between the exhaust tube and the lower unit. If someone has serviced the water pump (which I'm sure they have since 198?) and not renewed those seals (which have a lifespan of about 5-6 years before they get all hard and crusty) then you probably have some exhaust back-pressure adding to its fussyness.

[Creede]

From the way it acted the exhaust seal sounds like it could be the problem. Do the seals have a name? I can't find anything but seal kits online. Should I have the linkage syncronized anyway?

Thank you for the help

[fishinwrench]

It looks like this.

New fresh one in my hand. Old crusty leaking one is behind.

And yeah it sounds like it could use a good sync routine, most that I see are off a little so it's almost a given.

[Creede]

Thank you. I'm ordering a seal today. I'm also goin to get a service manual for the motor. Is synchronizing the linkage a very difficult process? I'm pretty comfortable working on my own stuff and have some knowledgeable help.

[fishinwrench]

Difficult, no. But to get the best results it requires an understanding of the entire engine.

A good manual will certainly get you there if you make absolutely sure that you understand everything that it is telling you, and why, before turning to the next page.

[Creede]

First of all thank you very much for all the help. I think I will get it with a manual. The guy helping me grew up in a small engine shop that his parents owned. Boat motors are just something new to us. I work in a heavy equipment shop so small motors are a little foreign to us. But I want to understand how it operates so I can handle future problems. I will post the results of a seal and sync

[fishinwrench]

Not a problem. I'm currently running a 1985 Evinrude 40hp on one of my rigs too and she's a sweetheart.

Love those motors!

[Creede]

Changed the exhaust seal and ran it in water. Same thing, fires up, will run choked but won't idle correctly and sounds like it's starving for fuel possibly? It may have pulled some trash from the fuel lines? I'm going to pull the carbs and check them over better. Exhaust seal was shot and needed changing anyway. Any suggestions are appreciated. Thank you

[fishinwrench]

The linkage sync is good now?

Before you go any further you probably should verify that compression is good (all cylinders within 15% of each other based on a 8 second crank cycle).

Then verify that you have strong and consistent ignition output (spark) on all secondary leads.

Then you can move your attention deeper into the fuel system.