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05-26-2017, 11:31 AM
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#1
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Senior Member
City: Tacoma, WA
Vessel Name: Matilda
Vessel Model: Ponderosa (CHB) 35' Sundeck
Join Date: Sep 2016
Posts: 130
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Dinghy outboard problem
I have a Johnson 8hp outboard on my small RIB. It has been working great for a long time, until last week. After running with it for about 30min, it suddenly dropped down to idle speed and would not accelerate. It did not die, it was still getting fuel, still had a spark, etc. But even turning the throttle full open would not give it much power. And even in neutral it would not rev very high at all.
I checked simple external things like the fuel line and the prop, but everything looked fine. I'm wondering what troubleshooting I could do to narrow down the cause of this problem. Or maybe the cause is common and already well-known?
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05-26-2017, 11:52 AM
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#2
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Guru
City: Campbell River
Vessel Name: Okisollo
Join Date: Apr 2012
Posts: 783
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Quote:
Originally Posted by schrater
I have a Johnson 8hp outboard on my small RIB. It has been working great for a long time, until last week. After running with it for about 30min, it suddenly dropped down to idle speed and would not accelerate. It did not die, it was still getting fuel, still had a spark, etc. But even turning the throttle full open would not give it much power. And even in neutral it would not rev very high at all.
I checked simple external things like the fuel line and the prop, but everything looked fine. I'm wondering what troubleshooting I could do to narrow down the cause of this problem. Or maybe the cause is common and already well-known?
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You don't mention it in your external checks but, when you turned the throttle handle did you see the the throttle on the carb open?
Check the throttle "vane" inside the carb, it may have come loose on the shaft.
Ted
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05-26-2017, 12:13 PM
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#3
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Senior Member
City: Lafayette, LA
Vessel Name: presently boatless
Join Date: Dec 2014
Posts: 350
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I'm assuming this is an older 2 stroker 8hp. Sounds to me the high speed jet in the carb is gummed up. Take apart the carb and clean it well.
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05-26-2017, 12:58 PM
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#4
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Valued Technical Contributor
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,775
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As others have noted, first check that the throttle plate in the carb is moving when you twist the throttle. If it is then as noted above, it is probably gummed up with ethanol related stuff.
Remove and dissasemble, then soak in a can of carburetor cleaner that you buy at an auto parts store. I have an 80% success rate with this procedure.
David
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05-26-2017, 12:59 PM
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#5
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Moderator Emeritus
City: Cameron, La
Vessel Name: Baobab
Vessel Model: Bayliner 4788
Join Date: Aug 2013
Posts: 2,660
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Quote:
Originally Posted by ragin cajun
I'm assuming this is an older 2 stroker 8hp. Sounds to me the high speed jet in the carb is gummed up. Take apart the carb and clean it well.
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Ragin Cajun is probably right but seeing as it is running, I would add a carb cleaner to my fuel and see if it cleans up before pulling the carb.
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05-26-2017, 01:09 PM
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#6
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Senior Member
City: Lafayette, LA
Vessel Name: presently boatless
Join Date: Dec 2014
Posts: 350
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Quote:
Originally Posted by dimer2
Ragin Cajun is probably right but seeing as it is running, I would add a carb cleaner to my fuel and see if it cleans up before pulling the carb.
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This is worth a try...Sea Foam works really well.
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05-26-2017, 01:55 PM
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#7
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Guru
City: Kenai, Alaska
Vessel Name: Melanie Rose
Vessel Model: 1999 Willard PH
Join Date: Feb 2013
Posts: 1,236
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Another for plugged jet, do a uTube search for how to clean your carb and do it. I had a bugger in my jet, probably because I was carrying the fuel tank on the swim platform and a little water migrated into the tank.
Got to love uTube :-)
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05-26-2017, 03:40 PM
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#8
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TF Site Team
City: Jacksonville
Join Date: Nov 2008
Posts: 11,670
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Quote:
Originally Posted by dimer2
Ragin Cajun is probably right but seeing as it is running, I would add a carb cleaner to my fuel and see if it cleans up before pulling the carb.
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Quote:
Originally Posted by ragin cajun
This is worth a try...Sea Foam works really well.
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Or just get the Sea Foam spray and use it directly into the carburetor. Short bursts vs a steady stream seem to work pretty good. You want to keep the engine running. I don't have the patience to mix the SeaFoam with the gas. I want it to work now!
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05-26-2017, 03:44 PM
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#9
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Guru
City: Full Time Cruising East Coast
Vessel Name: Meridian
Vessel Model: Krogen-42
Join Date: Aug 2011
Posts: 1,014
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Sea foam directly will not necessarily clean a clogged jet as the spray is upstream of the clog. But worth a try.
__________________
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Terry
Meridian
KK-42097
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05-26-2017, 04:54 PM
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#10
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Guru
Join Date: Jan 2010
Posts: 1,178
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Something to try and has on occasion work for me. Pull the fuel connector and run the motor dry. Tilt the motor up and pump the fuel ball. Start it and see how it runs if that will not clear your main jet the carburetor needs to be removed to disassembled and manually cleaned. You can spray anything you want in the carburetor it will not clear the debris in your jets
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05-26-2017, 04:57 PM
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#11
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,119
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First, check the fuel...if it phase separated from lack of use...a carb deep cleaning or rebuild is necessary.
Pour the gas out and see if it phase separated.
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05-26-2017, 05:06 PM
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#12
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Veteran Member
City: Puget Sound
Vessel Model: Currently boatless
Join Date: Aug 2015
Posts: 92
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I had the same problem on my 1 year old 4 stroke 4HP Tahatsu.
The solution was looking at a you tube video to know how the carb came off... Then, I pulled the carb off, removed the jets, cleaned the jets by just blowing the gunge out, cleaned the inside of the bowl with paper towels, put it back together and added fresh non-ethanol gas.
It took longer to pull the outboard off the dinghy onto the dock and put it back onto the dinghy after it was all cleaned then it took to clean the carb. It has ran great ever since.
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05-26-2017, 05:09 PM
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#13
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Guru
City: Sydney
Join Date: Jul 2015
Posts: 1,646
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Short answer REED VALVE
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06-04-2017, 05:34 PM
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#14
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Senior Member
City: Tacoma, WA
Vessel Name: Matilda
Vessel Model: Ponderosa (CHB) 35' Sundeck
Join Date: Sep 2016
Posts: 130
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Thanks to all who replied with helpful suggestions on this. For those following along at home, the carburetor actually ended up being very clean, but a small plastic part called the "cam follower" had snapped. This meant the throttle handle would turn without ever opening up the high speed jet. $10 replacement part and problem solved!
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06-07-2017, 08:16 AM
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#15
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Guru
City: LI or Fla
Join Date: Jul 2013
Posts: 1,148
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Good news, thanks for posting the results.
Ted get's the award for closest diagnoses over the internet!
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06-13-2017, 02:27 AM
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#16
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Guru
Join Date: Oct 2010
Posts: 519
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God I love a happy ending!!!!! take all the advice in relation to what you paid for it and approach life with informed open eyes and you will prosper. To al the contributers bravo! you are the rock against which judge my my whako mind!
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