boatbonanza
Cadet
- Joined
- Sep 18, 2010
- Messages
- 9
Hello,
I searched the forum archives but didn't find a similar problem so I am going to ask. I recently bought a 1990 VRO 120 Evinrude, it runs excellent but has a noise at low RPM. I would describe it as a tapping or soft knocking sound that is consistant with RPMs, more RPMs and the noise frequency increases but not necessarily the volume, in other words the noise gets faster but not louder. Noise is consistant in gear or out of gear, no change. Over about quarter throttle you don't hear it any more, I'm not sure if it quits or more likely you just can't hear it over the engine exhaust noise. At WOT it sounds perfect just like a new engine. These test were done at the lake. I came home and put it on muffs thinking I would be able to pinpoint the location of the noise better but with the exhaust unmuffled the tapping is almost unperceptable. I'm confident that I can still hear it but it is very faint because of the exhaust. I plan to try and find a water tank to try and use for testing but haven't been able to yet. Running on muffs I tried to listen closely and I believe that the noise is loudest at the exhust housing between the two cylinder banks. But very hard to tell for sure.
So far I did a compression test and found 115,117,123,122 PSI. Not excellent but not anything I see as an immediate problem. Thinking of a bearing issue I did the test where I take the piston a little past TDC then used a dowel rod to push the top of the piston to check for any play in a bearing, no movement at all on any cylinder.
For information sake I will say that within the last year this motor has had the fuel pump replaced, a new CDI ignition, pump impeller and NGK spark plugs. Any advise or ideas for trouble shooting would be appreciated. I'm mechanically inclined but not a lot of outboard experience, I have ordered a shop manual but haven't received it yet. My only idea is if it were an automobile I have heard an exhaust leak at the head sound like a ticking noise. Not knowing the design of this motor well I wan't sure if that is a possibility or not.
Thanks,
I searched the forum archives but didn't find a similar problem so I am going to ask. I recently bought a 1990 VRO 120 Evinrude, it runs excellent but has a noise at low RPM. I would describe it as a tapping or soft knocking sound that is consistant with RPMs, more RPMs and the noise frequency increases but not necessarily the volume, in other words the noise gets faster but not louder. Noise is consistant in gear or out of gear, no change. Over about quarter throttle you don't hear it any more, I'm not sure if it quits or more likely you just can't hear it over the engine exhaust noise. At WOT it sounds perfect just like a new engine. These test were done at the lake. I came home and put it on muffs thinking I would be able to pinpoint the location of the noise better but with the exhaust unmuffled the tapping is almost unperceptable. I'm confident that I can still hear it but it is very faint because of the exhaust. I plan to try and find a water tank to try and use for testing but haven't been able to yet. Running on muffs I tried to listen closely and I believe that the noise is loudest at the exhust housing between the two cylinder banks. But very hard to tell for sure.
So far I did a compression test and found 115,117,123,122 PSI. Not excellent but not anything I see as an immediate problem. Thinking of a bearing issue I did the test where I take the piston a little past TDC then used a dowel rod to push the top of the piston to check for any play in a bearing, no movement at all on any cylinder.
For information sake I will say that within the last year this motor has had the fuel pump replaced, a new CDI ignition, pump impeller and NGK spark plugs. Any advise or ideas for trouble shooting would be appreciated. I'm mechanically inclined but not a lot of outboard experience, I have ordered a shop manual but haven't received it yet. My only idea is if it were an automobile I have heard an exhaust leak at the head sound like a ticking noise. Not knowing the design of this motor well I wan't sure if that is a possibility or not.
Thanks,