High RPM at idle - 1800 - 3000 on shore

capslock118

Petty Officer 1st Class
Joined
Apr 27, 2009
Messages
249
Hi everyone.

Summary:
-In the driveway
-added sta-bil
-turned engine over to mix sta-bil and to drain carbs, started and was running at 2k idle. I knew this was high but I continued to let it run so I can close the season.
-engine was not running constant, it varied in RPM from 1800 - 3000, averaging 2,000, most of the time it held at around 2k.
-Once it starting averaging closer to 3,000 i turned the engine off, disconnected the fuel line then turned the engine back on to drain the carbs.
-this all occurred within the course of 5min - the engine did not indicate it got up to operating temps.

This past spring I was told that I needed my reed valves replaced from a mechanic I do not fully trust (this mechanic deals with all manufactures and is mostly a sales floor). A mechanic that I do trust 100% and more if I could said that didn't make any sense (100% mercury repair shop, no sales); and he fine tuned the idle screws this past spring.

Throughout the season, the engine was probably averaging an idle speed of about 1200; that's on the high end for sure.

I did notice that the in-line fuel filter still had liquid in it, i'm presuming it's fuel since I have a fuel/water separator.

I consider the engine closed for the season. I will probably not do anything to it until next spring as that is when I like doing all the mechanical work. So I intend this thread to serve as food for my thought until then, or if there is anything immediate I can check.

What are your thoughts?

things I have planned for next spring:
-idle timing adjustment
-new fuel lines on the engine block
-possibly reed valves and carb cleaning
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Re: High RPM at idle - 1800 - 3000 on shore

Do a link & sync according to your manual. It is important to do it in the steps given. Final adjustments must be done with the motor in the water and in gear.
 

capslock118

Petty Officer 1st Class
Joined
Apr 27, 2009
Messages
249
Re: High RPM at idle - 1800 - 3000 on shore

That's what I figured the answer would be.

What would explain the engine varying in RPM speed over the course of the 5 min though?

Seems to always happen when the boat is out of the water...
 
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