Hello Everyone,
I've need some guidance on where to go next in resolving a problem with my 1988 Mercury inline 6 outboard with 115hp.
Here's the problem
Engine has gradually decreased MAX RPM during WOT from about 5,000 rpm at the begining of spring to roughly 4,000 RPM now. When you push the throttle to WOT it quickly gets to 3,500 then sort of stumbles to finally reach 4,000. I am not having a problem with idle and the engine always starts up every time.
Here's what I have checked
My next steps unless I hear other ideas here...
Any other thoughts?
I've need some guidance on where to go next in resolving a problem with my 1988 Mercury inline 6 outboard with 115hp.
Here's the problem
Engine has gradually decreased MAX RPM during WOT from about 5,000 rpm at the begining of spring to roughly 4,000 RPM now. When you push the throttle to WOT it quickly gets to 3,500 then sort of stumbles to finally reach 4,000. I am not having a problem with idle and the engine always starts up every time.
Here's what I have checked
- Using a timing light I confirmed that all plugs (or at least the wires) are firing at all speeds
- I have changed the fuel / water separator
- I have changed the fuel filter
- I have changed the spark plugs
- I tried to test compression but couldn't get a good reading with the cheap loaner gauge from AutoZone.
- I have a glass fuel filter so I can see fuel flow at WOT, the fuel filter bowl stays full of fuel at all speeds
My next steps unless I hear other ideas here...
- Find a good compression guage and do an accurate check
- Clean and rebuild the carbs
Any other thoughts?