canoemang
Petty Officer 1st Class
- Joined
- Apr 9, 2011
- Messages
- 350
1984 mercury 115 inline 6 (6524769)
I am having an issue with RPM's dropping at WOT. At WOT it jumps up to 5100 RPM and slowly drops down to 4900 then surges back up to 5100 and so on. When it surges it sounds like it is running strong then tapers down to 4900, also all 6 plug's have drops of black oil. I prime it and no gas leaks at all and the primer bulb holds pressure.
It has a jet lower unit (from outboard jets) with a 4 blade aluminum impeller (shimmed correctly) and is pushing an Alweld 1856 (1400 lbs). The rpm surge is not cavitation of the jet, i have intake fins and it is sucking water the whole time.
So far I have:
Rebuilt fuel pump
Rebuilt all 3 carb's (maybe floats need to be readjusted and is currently running to rich?)
Installed new Gas lines from tank on through
Link and sync (set max timing on the water wot @ 21 degs
CDI Switch boxes
CDI stator
CDI trigger
Coil packs test good (resistance test in spec)
Strong spark on all 6 cylinderz
Hooked and inductive timing light to each plug wire 1 at a time during wot, no miss at wot
Compression is 120 on all 6
New inner exhaust baffle gasket (was leaking and water droplets was on #3 spark plug, fixed)
Both of the water jacket gaskets I did when I did inner exhaust gasket
New port gasket (was leaking also)
91 Octane gas with no ethanol, mixed 50-1 with quicksilver 2 stroke mercury oil.
I currently have the idle mixture screw set at 1 1/4 turns out, it has given the best performance at hole shot and wot.
I am having an issue with RPM's dropping at WOT. At WOT it jumps up to 5100 RPM and slowly drops down to 4900 then surges back up to 5100 and so on. When it surges it sounds like it is running strong then tapers down to 4900, also all 6 plug's have drops of black oil. I prime it and no gas leaks at all and the primer bulb holds pressure.
It has a jet lower unit (from outboard jets) with a 4 blade aluminum impeller (shimmed correctly) and is pushing an Alweld 1856 (1400 lbs). The rpm surge is not cavitation of the jet, i have intake fins and it is sucking water the whole time.
So far I have:
Rebuilt fuel pump
Rebuilt all 3 carb's (maybe floats need to be readjusted and is currently running to rich?)
Installed new Gas lines from tank on through
Link and sync (set max timing on the water wot @ 21 degs
CDI Switch boxes
CDI stator
CDI trigger
Coil packs test good (resistance test in spec)
Strong spark on all 6 cylinderz
Hooked and inductive timing light to each plug wire 1 at a time during wot, no miss at wot
Compression is 120 on all 6
New inner exhaust baffle gasket (was leaking and water droplets was on #3 spark plug, fixed)
Both of the water jacket gaskets I did when I did inner exhaust gasket
New port gasket (was leaking also)
91 Octane gas with no ethanol, mixed 50-1 with quicksilver 2 stroke mercury oil.
I currently have the idle mixture screw set at 1 1/4 turns out, it has given the best performance at hole shot and wot.