mrcrunchybeans
New member
Hey! Long time lurker - and it's finally time to ask for help.
Pictures: https://imgur.com/a/RoGnEns
Video of Engine Idling Fast: https://youtu.be/pe0y5lGvo0k
Serial Number: 0b300098
Model Number: 1115452BD
I've got a (new to me) 1988 Mercury 115hp Oil-Injected [tower of power?] engine. The previous owner did not have any maintenance records on it, which led me to do a complete tune-up before getting too comfortable with it.
I bought 3x carburetor rebuild kits and rebuilt the carbs. I also replaced the fuel filter, added seafoam, tuned the timing, replaced the spark-plugs. Replaced the water pressure gauge, added a trim sensor, drained and replaced the lower unit oil, lubricated the linkages, added a second battery to isolate the starter from the accessories and the BlueSea Add-A-Battery kit.
This is my first boat, and quite honestly, I'm not sure 100% what it is "supposed" to sound like. My Seloc manual says that idle speed is supposed to be at 650rpm in forward gear at idle, but my tach read closer to 3400rpm! It seems like a vacuum leak, so I used my propane torch trying to find a leak somewhere, but failed. I then rebuilt the carbs again, to see what I missed (and actually I rebuilt them all 5 times at this point). Still, same thing.
The only "symptom" I have noticed is that it is idling fast. To my untrained ear, the engine sounds to pur nicely, and it operates well on the water. My fear is that if it is truly idling at such high rpm, that I will destroy my lower unit.
I decided that maybe my tach was wrong, so I checked the back of it and it had a dial to calibrate, which I moved and no longer trust the onboard tach. So I bought an inductive tach that wraps around the spark plug wire. That tach reads that my current idle speed is 2900rpm!
I'm at a lost at what else to do to isolate the problem. Any help would be appreciated.
Compression Test:
C1 - 107 107 107
C2 - 106 106 106
C3 - 105 105 105
C4 - 107 107 107
C5 - 103 103 103
C6 - 103 103 103
-Brian
Pictures: https://imgur.com/a/RoGnEns
Video of Engine Idling Fast: https://youtu.be/pe0y5lGvo0k
Serial Number: 0b300098
Model Number: 1115452BD
I've got a (new to me) 1988 Mercury 115hp Oil-Injected [tower of power?] engine. The previous owner did not have any maintenance records on it, which led me to do a complete tune-up before getting too comfortable with it.
I bought 3x carburetor rebuild kits and rebuilt the carbs. I also replaced the fuel filter, added seafoam, tuned the timing, replaced the spark-plugs. Replaced the water pressure gauge, added a trim sensor, drained and replaced the lower unit oil, lubricated the linkages, added a second battery to isolate the starter from the accessories and the BlueSea Add-A-Battery kit.
This is my first boat, and quite honestly, I'm not sure 100% what it is "supposed" to sound like. My Seloc manual says that idle speed is supposed to be at 650rpm in forward gear at idle, but my tach read closer to 3400rpm! It seems like a vacuum leak, so I used my propane torch trying to find a leak somewhere, but failed. I then rebuilt the carbs again, to see what I missed (and actually I rebuilt them all 5 times at this point). Still, same thing.
The only "symptom" I have noticed is that it is idling fast. To my untrained ear, the engine sounds to pur nicely, and it operates well on the water. My fear is that if it is truly idling at such high rpm, that I will destroy my lower unit.
I decided that maybe my tach was wrong, so I checked the back of it and it had a dial to calibrate, which I moved and no longer trust the onboard tach. So I bought an inductive tach that wraps around the spark plug wire. That tach reads that my current idle speed is 2900rpm!
I'm at a lost at what else to do to isolate the problem. Any help would be appreciated.
Compression Test:
C1 - 107 107 107
C2 - 106 106 106
C3 - 105 105 105
C4 - 107 107 107
C5 - 103 103 103
C6 - 103 103 103
-Brian