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Johnson 40hp? not sure of year maybe 80s or 90s, running badly and needs to run rich to idle and have power

L

lucayoyom

New member
runs great for 10 minutes on water and then its stuck at 5kph for the rest of the trip with super low rpms at full throttle in gear, If i clean the spark plugs if works maybe once or twice for about a couple minutes, out of gear i can rev it up to max rpm but for about 1 second when putting full throttle it goes fast and then gets stuck to slow again.
 
Model # is ?----The trouble shooting starts with a compression test.-----Post the actual values here.---Does spark jump a gap of at least 3/8" on both leads?----Running with VRO or 50:1 mix>---What type of fuel tank?----Does primer bulb go hard?-----Do not rev it up high in neutral/
 
racerone said:
Model # is ?----The trouble shooting starts with a compression test.-----Post the actual values here.---Does spark jump a gap of at least 3/8" on both leads?----Running with VRO or 50:1 mix>---What type of fuel tank?----Does primer bulb go hard?-----Do not rev it up high in neutral/
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Hi thanks for reply, old owner painted over the tag or removed it, not sure how to see model number, compression is 125psi both cylinders, im running 50:1 mix with new fuel lines from tank and a hard bulb, not sure how to measure the spark jumping gap?
 
Buy an air gap tester, or make something out of scraps, like this. The end with the bolt goes into the sparkplug boot, ground the other in a sparkplug hole
 

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WOW you should get a patent Ed. I'm green with envy. This little simple tool can save a lot of trouble.
How long did the motor sit idle and was it ever used with regular fuel? If one carb is partially plugged it will score that cylinder then you are in trouble.
 
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timguy said:
WOW you should get a patent Ed. I'm green with envy. This little simple tool can save a lot of trouble.
How long did the motor sit idle and was it ever used with regular fuel? If one carb is partially plugged it will score that cylinder then you are in trouble.
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I just bought the boat and he said it was rebuilt, think i got sold a lemon in terms if the motor, the actual boat is great haha 🫠, ill clean out the carbs today and check the timing, do u know what advance it should have to run good? Thanks
 
Timing should be okay for now. Concentrate on carb cleaning and synchronizing so they open IDENTICALLY. Checking carb follower so it contacts at the mark. Carbs, likely once removed/reinstalled, will not be in the exact position where you removed them thereby changing the synchronization because of slop in the flange holes. If carbs are not synchronized and especially at idle or trolling....one cylinder may run dryer than the other and possibly get scored. If you need cylinder heads/bolts or depending on what you find, call Tim's Outboard in Hackensack Minnesota at 218682-2331 and they will help you, tell them that Tim sent you.
 
timguy said:
Timing should be okay for now. Concentrate on carb cleaning and synchronizing so they open IDENTICALLY. Checking carb follower so it contacts at the mark. Carbs, likely once removed/reinstalled, will not be in the exact position where you removed them thereby changing the synchronization because of slop in the flange holes. If carbs are not synchronized and especially at idle or trolling....one cylinder may run dryer than the other and possibly get scored. If you need cylinder heads/bolts or depending on what you find, call Tim's Outboard in Hackensack Minnesota at 218682-2331 and they will help you, tell them that Tim sent you.
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Hi thanks for the info, ill check all that aswell. Hopefully i havent scored the cylinder. Im from new zealand so ill have to try find parts here but its a bit hard for sure haha
 
Yes New Zealand is incredibly beautiful. I have been to Australia, my brother many trips to NZ. I think he invested with someone in land near Christchurch. He rents a bike whenever he goes. If you need parts, he goes back every year.
 
Land of the Long White Cloud. Rented a broken down Toyota years ago, drove around the entire North Island. Saw the only de Havilland Rapide I’ve ever seen at an airport I’ve forgotten. About 6 years ago, toured, & walked some good sections of the South Island. Shame to see the earthquake damage in Christchurch.
Over here in Canada, there are hundreds of Kiwis working at the ski hills during our winter.
 
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