idle problem on a 40hp 1985 mariner outboard

[TERRY W KUBIAK]

what can I do to slow down the idle speed on a 1985 mariner 2 cylinder outboard?

 

[boscoe]

Is the idle speed in specification or out of specification?

Are you trying to slow down the idle RPM of the motor or is the objective to slow down the speed of the boat when the motor is at idle RPM?

What is the engine ID?

 

[TERRY W KUBIAK]

It’s a 1985 Mariner 40 hp, 40EL 6E9 L 420631. I’ve got the idle screw turned down all the way and it still is idling too fast. I would like to slow it down so that it won’t klunk so hard when I shift it.

 

[boscoe]

Specification is 800 RPM in neutral. Is that what you are seeing? That or maybe a tad lower.

Is the propeller stainless steel or aluminium?

There are propellers that have a shift dampening hub but I can't recall if there is one available for low HP models.

 

[TERRY W KUBIAK]

Aluminum prop, idle speed is way higher than 800 rpm.

 

[boscoe]

Now you have to find and fix the problem that is causing the high RPM.

 

[racerone]

Checked flywheel key?

 

[TERRY W KUBIAK]

Checked flywheel key?

I’m not understanding what that has to do with idle, prior the boat ran strong for 30-40 minutes , but it idles too fast.

 

[boscoe]

I would be suspecting an air leak of some sort.

 

[TERRY W KUBIAK]

Do you mean around the carburetors? Would it be worth it to rebuild the carburetors or would it be better to just replace them with new OEM carburetors?

 

[No-Fish Nubi]

It doesn't appear that the original poster was able to resolve his issue, which is the same one I have - two years after this post, I just bought a sixteen-foot runabout equipped with a Mariner 40EL 6E9 L (long shaft) and a six-digit serial number (416281). I have to mix the oil with the gas, it's not oil-injected (according to the guy I bought it from). All the parts and manual search engines seem to be restricted to seven-digit serial numbers. Claude.ai can't find the exact model year, citing "conflicting public serial number lists," and nothing comes up for that serial number when I search the official Mariner shop manual page, marineengine.com, and crowleymarine.com. I guess I'll keep poking around this forum and see if anyone knows what this mystery engine is and how to make sure I'm ordering the right parts. Claude.ai did tell me it's basically a Yamaha engine re-branded "Mariner" so I'll check that out, too. I'd appreciate anyone with more info about this engine to reply.