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Hondas 150 HP stalling at idle.

P

Pohnpei Surf Club

Member
Hello everyone.
I have twin Hondas 150 hp, purchased around 2021 with 2,400 hours.
Both are stalling at idle, needing a bit more of crank time to start, or stalling once you slow down into idle.
The RPM's seem a bit to slow at idle, specially on a cold motor.
The spark plus are new and on one of them I just change the entire fuel system and pump, water separator.
Any tips on what I need to fix, or how to higher up a bit the rpm's at idle and stop the stalling at low RPM's??
Thank you, Allois.
 
Hi,
No expert here...I"'ve never worked on a 150 Honda.
But the electronic air control valve... item 20 in the link (although the number 20 is obscured by the "boats.net" lettering) is a major factor in controling idle speed.

A common problem is that the little filter screen for that valve can get dirty. Item 19.

Often, simply cleaning that screen can restore the idle so it might be the first thing you would want to try.


Beyond that, the throttle body (item 2 in link below) can get dirty and need cleaning. That should be done with throttle body cleaner only and no scrubbing.


In addition to that, there is an idle set screw (item 1) but often that adjustment has an accompanying procedure to follow so consulting the shop manual would be advised before "playing" with that willy-nilly.

Shop manual available here:

Honda Marine | Shop Manuals Publications | Honda Power Products Support Publications

publications.powerequipment.honda.com publications.powerequipment.honda.com

There are some free downloads listed on that site as well so be sure to check those out.

Good luck
 
Last edited:
I would do a valve adjustment as specified in the shop manual, in addition to the above recommendations. From what I read here, it’s best not to play with the idle adjustment screw on a fuel injected Honda outboard, unless all else fails.

Clean fresh fuel with something like sea foam added to it is needed. Run a heavy dose of sea foam on your next run, keep it at high speed to get fuel and valve passages hot and flushed. Keep a close eye on the water separator filter for contamination like sediment or cloudy old fuel. Watch your spark plugs to see they are not showing something bad happening. Buy good clean fuel, ethanol free if possible, I burn 91 octane, the highest octane available.

My 1999 130hp FI, it had a stalling issue at low rpm while docking, a good fuel cleanout cured my problem.
 
NSDON gives good advice here. Not only with fuel treatment but with the valve adjustment. Something I should have remembered to suggest when I replied.

Good luck.
 
You may not have a local supply of sea foam?😁
I live near the town of Mahone Bay, Nova Scotia, Canada. Our boating season is about June 1 to early October, I don’t burn as much fuel as you do.
 
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