I have a 1989 48hp johnson. The engine starts right up and runs great at top speed for about an hour. After that, the engine starts to shudder and jerk. At that point it will run smoothly at low speed, but if i give it any gas it starts shuddering again. I am thinking that one of the carbs needs to be adjusted, but I am not sure.
THoughts?
Thanks,
Shudder and jerk like its misfiring? If so I would lean toward an ignition issue not fuel.
Disclaimer: I am not an outboard technician, nor did I stay at a Holiday Inn Express last night.
The engine starts fine, are you thinking its a spark plug or fuel injector issue?
ShrimpPimp207
sounds like the motor is going into rpm reduction from overheat, and your alarm just isn’t going off.
if you shut it down for a while and restart does it work normally for a while?
Ignition as in spark, not starter. Parts include: coil, power pack, rectifier, stator, timer base.
These parts will sometimes operate fine until they get hot.
Listen to Chris V. He knows much more than I.
I put some fuel system cleaner in the fuel and took it out yesterday. Now the issue is immediate when I attempt to give the engine any gas. It runs great at low speed, but I cannot give it any gas now. I am using an old omc gas tank, so I am going to take that apart next to check the intake. If that isnt it, I may have to find someone to work on it.
Stater and trigger
Water pump impeller or thermostat. How’s the stream look while its running? Listen to Chris V, he knows what he’s talking about.
'06 Mckee Craft
184 Marathon
DF140 Suzuki
Impeller seems to be working as it is pulling in water and spitting it out up top. I will check the thermostat next.
air fuel or spark, there isn’t anything else.
only way I work is to start at the beginning
compression
spark there is lot of variables here
fuel
Check your roller sleeve assembly.(small ruber piec that rides in the cam lever to control timing) they ruber sleeve dry rots over time eventually falling off completely. When this happens the timing lever no longer makes contact with the throttle lever therefor not allowing for correct timing changes when opening the throttle. I think its a 4 dollar part but it can sure cause a lot of headache!
It really could be any of the things mentioned already. Sounds more like ign or over heating to me. Or maybe a combination of both:smiley:
Thank you all for the input. I will try of few of your suggestions and then get a mechanic involved if i cant get it figured out.
Best Regards,
ShrimpPimp207
Go get the OMC technical manual or the SELOC. Either will have a trouble shooting tree pointing to the procedure to test each branch of the tree. Like Chris said, air fuel spark. I’d add mechanical (on an older worn motor, there could be bearing/seal/bent or corroded shaft/etc). Or, just take it to Chris… or whomever you prefer.
ps - some people apparently greatly prefer the OMC publication to the SELOC publication. I have the SELOC for my 1995 Johnson 88spl and it covers everything I need… so far…
17’ Henry O Hornet
26’ Palmer Scott