Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-07-2014, 14:49   #1
Registered User

Join Date: Apr 2013
Posts: 28
Outboard Motor Acting Up - Idle Speed Only

I have an old Johnson 2-stroke 50 HP outboard that's been acting up. When underway, it runs fine for a bit, but after a while of increased throttle the motor dies down to idle speed. However, when the squeeze ball is pumped it has gone back up again, but then later again returns to idle speed.

We checked both carburetors and they look clean. We also replaced both spark plugs and the fuel filter.

We considered the fuel pump - but this would seem either to work not at all or work fine - not be "kind of needing replacement" - similar to a spun prop which we also considered and ruled out since it has managed to rise above idle speed at times.

Any other considerations/suggestions?

Thanks!
__________________

__________________
MrAntigone is offline   Reply With Quote
Old 12-07-2014, 15:12   #2
Registered User
 
sparrowhawk1's Avatar

Join Date: Jan 2014
Location: Miami Beach Fl
Boat: Colombia Cc 11.8
Posts: 1,252
Just to clarify: you can get it to run fine by squeezing the bulb?
__________________

__________________
sparrowhawk1 is online now   Reply With Quote
Old 12-07-2014, 15:35   #3
Registered User

Join Date: Feb 2009
Posts: 1,848
Re: Outboard Motor Acting Up - Idle Speed Only

You need a new fuel pump
__________________
motion30 is offline   Reply With Quote
Old 12-07-2014, 15:35   #4
Moderator
 
JPA Cate's Avatar

Join Date: Nov 2011
Location: aboard, cruising in Australia
Boat: Sayer 46' Solent rig sloop
Posts: 10,715
Re: Outboard Motor Acting Up - Idle Speed Only

When you checked the carbs, did you blow out the jets? check the fuel for any kind of particulate matter?

[Had a spun prop, it would only work at idle.]

Ann
__________________
Ann, with Jim, aboard US s/v Insatiable II, in Oz, very long term cruisers
JPA Cate is online now   Reply With Quote
Old 12-07-2014, 16:45   #5
Registered User
 
Reefmagnet's Avatar

Join Date: May 2008
Location: puɐןsuǝǝnb 'ʎɐʞɔɐɯ
Boat: Nantucket Island 33
Posts: 2,737
Re: Outboard Motor Acting Up - Idle Speed Only

Check the tank vent is open/working.
__________________
Reefmagnet is offline   Reply With Quote
Old 12-07-2014, 17:44   #6
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 7,963
Re: Outboard Motor Acting Up - Idle Speed Only

Only realistic way to check/clean carbs is to tear them down, clean (careful w the jets), and reassemble.

Re fuel pump. Sometimes the diaphram gets perforated and can cause issues other than work/not work. That's inexpensive and easy to replace.

Maybe a vaccum leak. They can be intermittent and only occur after sufficient vaccum has built up...like after a few minutes of running.

Tank vent. On the outside chance that you have an obstruction there check/clean. You can also make a run with tank cap loose to confirm vaccum is not forming in tank.

Another thought along these lines: is it a portable tank or permanent install? If perm, is vent on cap or seperate vent line?

If you don't get off that easy then:

Clean the carbs.

Inspect the fuel pump (esp diaphram).

Check all fitings on vaccum side of fuel line from pump to tank.
__________________
belizesailor is offline   Reply With Quote
Old 12-07-2014, 17:57   #7
Registered User
 
sparrowhawk1's Avatar

Join Date: Jan 2014
Location: Miami Beach Fl
Boat: Colombia Cc 11.8
Posts: 1,252
If There was a problem with the fuel tank vent you would not be able to pump fuel through the ball it would stay collapsed. Most likely it's an air leak. first place I would look is at the hose connector to the engine. Usually if air is leaking in if you pump on the ball fuel will leak out. second place: the hose connector to the tank which is easier because all you have to do is disconnect it put the hose in the tank. For checking for the leaks on any hoses on the engine or even the fuel pump case once again use the ball pump to pressurize the system and look for leaks
__________________
sparrowhawk1 is online now   Reply With Quote
Old 12-07-2014, 18:08   #8
Moderator Emeritus
 
Ex-Calif's Avatar

Cruisers Forum Supporter

Join Date: May 2007
Location: Singapore
Boat: Maxi 77 - Relax Lah!
Posts: 11,514
Images: 4
Re: Outboard Motor Acting Up - Idle Speed Only

Observe the fuel filter while running - use opaque filters. You can see the air bubble growing.

Fix the suction air side leak.

Double check the vent - while it may not be totally blocked, it could be restricted.

There is no debris in the tank, right?

Only other thought is, "What boat is this engine powering and has the tank been relocated recently?" i.e. lowered in the hull so the lift is higher.
__________________
Relax Lah! is For Sale <--- Click
Click--> Custom CF Google Search or CF Rules
You're gonna need a bigger boat... - Martin Brody
Ex-Calif is offline   Reply With Quote
Old 12-07-2014, 18:59   #9
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 7,963
Re: Outboard Motor Acting Up - Idle Speed Only

Quote:
Originally Posted by Ex-Calif View Post
Observe the fuel filter while running - use opaque filters. You can see the air bubble growing.
....
Cleaned/Changed your fuel filter lately? These symptoms are similar to a clogged filter too.

Should at least add that to the list to things to check.
__________________
belizesailor is offline   Reply With Quote
Old 12-07-2014, 21:52   #10
Registered User
 
NoTies's Avatar

Join Date: Nov 2005
Location: Vanuatu
Boat: Whiting 29' extended "Nightcap"
Posts: 1,378
Images: 2
Re: Outboard Motor Acting Up - Idle Speed Only

Don't forget the filter inside the tank on the pick up
__________________
Pete

Positively, socially deviant.
NoTies is offline   Reply With Quote
Old 14-07-2014, 15:22   #11
Registered User

Join Date: Nov 2012
Location: French Polynesia
Boat: Allied 39
Posts: 470
Re: Outboard Motor Acting Up - Idle Speed Only

That is exactly what happened to my Yamaha 8hp Enduro a few weeks ago.. Exactly! Everyone said fuel pump. But what it turned out to be was an old hose fitting. Replaced the hose with a Yamaha version, cleaned the tank, removed and cleaned the carb. Blew the jets out, etc.

Been working like a champ now.

My suggestion. Is to do all the regular checks before you spring for a new fuel pump.

How old is the fuel?

Good luck

Chuck


Sent from my iPad using Cruisers Sailing Forum
__________________
www.jacarandajourney.com
chouliha is offline   Reply With Quote
Old 14-07-2014, 15:38   #12
Registered User
 
cwyckham's Avatar

Join Date: Apr 2011
Location: Vancouver, BC
Boat: Niagara 35
Posts: 1,870
Re: Outboard Motor Acting Up - Idle Speed Only

A simple mistake that I've made three times now: Fuel goes bad, especially mixed fuel. If the gas isn't fresh, start by buying brand new fuel from a source that gets a lot of turnover. Only then start trouble shooting the engine itself.
__________________

__________________
cwyckham is offline   Reply With Quote
Reply

Tags
motor, outboard

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Perkins 4.108 Idle Speed Adjustment Astral Blue Engines and Propulsion Systems 6 09-04-2013 04:37
New Member Question Regarding Idle Speed jeffcowt Engines and Propulsion Systems 9 04-09-2011 14:16
High Oil Pressure - Only at Idle windsaloft Engines and Propulsion Systems 10 22-04-2011 08:10
Adjusting 2qm15 idle speed Derrick Serrer Engines and Propulsion Systems 4 09-08-2008 10:35
Engine idle woes-Will not idle after warm Pa La O La Engines and Propulsion Systems 5 24-09-2006 13:13



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:07.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.