Dinghy outboard problem

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schrater

schrater

Senior Member
Joined
Sep 4, 2016
Messages
130
Location
USA
Vessel Name
Matilda
Vessel Make
Ponderosa (CHB) 35' Sundeck
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?
 
schrater said:
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?
Click to expand...

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
 
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.
 
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
 
ragin cajun said:
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.
Click to expand...

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.
 
dimer2 said:
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.
Click to expand...

This is worth a try...Sea Foam works really well.
 
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 :)
 
dimer2 said:
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.
Click to expand...

ragin cajun said:
This is worth a try...Sea Foam works really well.
Click to expand...

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! :D
 
Sea foam directly will not necessarily clean a clogged jet as the spray is upstream of the clog. But worth a try.
 
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
 
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.
 
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.
 
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!
IMG_5795.JPG
 
Good news, thanks for posting the results.

Ted get's the award for closest diagnoses over the internet!
 
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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