What's causing a "soft" miss or backfire at low RPM's? 1999 Mercury 15 2 stroke
Brought the engine from the lake(3500ft), down to the ocean for the summer. Probably put maybe 5hrs on it since. Had it serviced before using it down here. Wasn't too happy with them, as they charged me almost $400 to change 2 plugs, gear oil and lube the nipples. Engine was covered in rust dust too when it came back. Wasn't impressed with them at all. Thought it would have been a good idea to get a professional to take a look at it since it's been over 10years, but I have many mechanical family members who help take care of all the engine toys at the lake. Still, I though it couldn't hurt to get these guys to service and give a once over. They said everything seemed fine and gave it back (covered in rust dust!)
Never had any problems with this engine, and she still looks brand new, especially under the cover!
She starts fine. Pull the choke and crank a couple times and she starts right up. A little rough idle when cold, but never dies. Once she warms up, she seems to have a rhythmic miss when idling or trolling. At high rpm's she seems to smooth out completely.
So now today and the other day I noticed a weird thing happening when trolling around at low rpm's. There would be a quick, "soft" miss or backfire and a puff of smoke, then back to normal. Almost made me think I hit something and broke a prop pin, but it was so quick and she never dies. Would only seem to happen when in gear and under a little throttle, but still slow and no where near planing. Also notice that it kinda lags and feels "rough" in the first half when accelerating to full, but then becomes quick and smooth once rpm's come up past half way or so.
I pulled the plugs today and they seem normal(they only have about 5hrs on them) They are dry and brown, with little to no deposits. The only sign of oil is around the plug threads
So this has me worried. Does this sound like symptoms of a lean engine? Maybe there is a high altitude jet installed? I'm hoping it's maybe a fuel issue? I try to run my fuel/oil about 75:1. I think 100:1 is recommended and 50:1 for commercial use, so I figure 75:1 is probably good, especially in the salt water.
Any ideas?
Thanks
Brought the engine from the lake(3500ft), down to the ocean for the summer. Probably put maybe 5hrs on it since. Had it serviced before using it down here. Wasn't too happy with them, as they charged me almost $400 to change 2 plugs, gear oil and lube the nipples. Engine was covered in rust dust too when it came back. Wasn't impressed with them at all. Thought it would have been a good idea to get a professional to take a look at it since it's been over 10years, but I have many mechanical family members who help take care of all the engine toys at the lake. Still, I though it couldn't hurt to get these guys to service and give a once over. They said everything seemed fine and gave it back (covered in rust dust!)
Never had any problems with this engine, and she still looks brand new, especially under the cover!
She starts fine. Pull the choke and crank a couple times and she starts right up. A little rough idle when cold, but never dies. Once she warms up, she seems to have a rhythmic miss when idling or trolling. At high rpm's she seems to smooth out completely.
So now today and the other day I noticed a weird thing happening when trolling around at low rpm's. There would be a quick, "soft" miss or backfire and a puff of smoke, then back to normal. Almost made me think I hit something and broke a prop pin, but it was so quick and she never dies. Would only seem to happen when in gear and under a little throttle, but still slow and no where near planing. Also notice that it kinda lags and feels "rough" in the first half when accelerating to full, but then becomes quick and smooth once rpm's come up past half way or so.
I pulled the plugs today and they seem normal(they only have about 5hrs on them) They are dry and brown, with little to no deposits. The only sign of oil is around the plug threads
So this has me worried. Does this sound like symptoms of a lean engine? Maybe there is a high altitude jet installed? I'm hoping it's maybe a fuel issue? I try to run my fuel/oil about 75:1. I think 100:1 is recommended and 50:1 for commercial use, so I figure 75:1 is probably good, especially in the salt water.
Any ideas?
Thanks
