Good evening fellow boaters.
I need help troubleshooting my outboard engine.
I have a Yamaha 30HP two-stroke outboard engine, model 30HMH.
This outboard was purchased new in January 2022, and has run without any troubles. We use it several times per week, so it’s doesn’t sit unused. On average we go through a 5 gallon tank of fuel every two or three weeks.
Today it started, but I noticed it didn’t sound the same - running rough, if that makes any sense. When I tried to load it, it seemed to have no power. It wouldn’t rev-up much. Sounds like it’s bogging down, a term I’ve heard used when a car is shifted into a gearthat’s too high for the speed of the car… the engine doesn’t have enough power and sounds “bogged down”.
There is also some sputtering, like it was out of fuel. There was a few strange misfires, which made me wonder if the fuel has water in it.
My troubleshooting thus far is described below, which has not revealed the problem.
Spark plugs, a bit oily and some carbon, but otherwise good. I cleaned them up and used a bit of emery paper to be sure the electrodes were clean.
I dumped the fuel and installed new, checking for any evidence of water or dirt - none found.
I checked the fuel filter on the engine and saw very tiny particles, but nothing significant. I checked the filter for minor tears, none found.
I disassembled the diaphragm fuel pump, and it appears fine, with the metal flaps looking perfect, and the diaphragm intact, not ripped.
I opened the carburetor and remove the float and needle, which look perfectly new - no wear, debris, or accumulation of anything. The entire carburetor looks like it’s never been used - whistle clean. I could see micro holes in the round chamber where air flows through, and there’s zero trace of any accumulation or gunk (like from ethanol fuels). Probably the fuel I’m using in the Caribbeanis not EPA compliant and isn’t susceptible to gunking up the carburetor. I didn’t disassemble further.
I confirmed proper functioning of the choke and its linkages and the throttle and its linkages.
I’ve tried using the fuel-line pressure bulb to add fuel pressure while running the engine under load, and there was no improvement. The engine cannot deliver much power, and it seems to me that even under zero load the RPM acceleration is hesitating. I also feel the engine is not running as smooth as it used to when at idle or higher RPM’s. Seems to shake a bit more than I remember.
I don’t have a compression gauge, but I think this is my next step. I also think it might be worth replacing the fuel pump even though it seems to be fine (complete disassembly for inspection was conducted).
Obviously I’ve missed the troubleshooting steps that will eventually diagnose this issue. Hopefully those with experience or expertise can suggest next steps.
Sincerely,
Randy
I need help troubleshooting my outboard engine.
I have a Yamaha 30HP two-stroke outboard engine, model 30HMH.
This outboard was purchased new in January 2022, and has run without any troubles. We use it several times per week, so it’s doesn’t sit unused. On average we go through a 5 gallon tank of fuel every two or three weeks.
Today it started, but I noticed it didn’t sound the same - running rough, if that makes any sense. When I tried to load it, it seemed to have no power. It wouldn’t rev-up much. Sounds like it’s bogging down, a term I’ve heard used when a car is shifted into a gearthat’s too high for the speed of the car… the engine doesn’t have enough power and sounds “bogged down”.
There is also some sputtering, like it was out of fuel. There was a few strange misfires, which made me wonder if the fuel has water in it.
My troubleshooting thus far is described below, which has not revealed the problem.
Spark plugs, a bit oily and some carbon, but otherwise good. I cleaned them up and used a bit of emery paper to be sure the electrodes were clean.
I dumped the fuel and installed new, checking for any evidence of water or dirt - none found.
I checked the fuel filter on the engine and saw very tiny particles, but nothing significant. I checked the filter for minor tears, none found.
I disassembled the diaphragm fuel pump, and it appears fine, with the metal flaps looking perfect, and the diaphragm intact, not ripped.
I opened the carburetor and remove the float and needle, which look perfectly new - no wear, debris, or accumulation of anything. The entire carburetor looks like it’s never been used - whistle clean. I could see micro holes in the round chamber where air flows through, and there’s zero trace of any accumulation or gunk (like from ethanol fuels). Probably the fuel I’m using in the Caribbeanis not EPA compliant and isn’t susceptible to gunking up the carburetor. I didn’t disassemble further.
I confirmed proper functioning of the choke and its linkages and the throttle and its linkages.
I’ve tried using the fuel-line pressure bulb to add fuel pressure while running the engine under load, and there was no improvement. The engine cannot deliver much power, and it seems to me that even under zero load the RPM acceleration is hesitating. I also feel the engine is not running as smooth as it used to when at idle or higher RPM’s. Seems to shake a bit more than I remember.
I don’t have a compression gauge, but I think this is my next step. I also think it might be worth replacing the fuel pump even though it seems to be fine (complete disassembly for inspection was conducted).
Obviously I’ve missed the troubleshooting steps that will eventually diagnose this issue. Hopefully those with experience or expertise can suggest next steps.
Sincerely,
Randy
