Just wondering if anyone has come across this problem. Early spring I was running 51 – 52 GPS speed. In April my 200 Mercury EFI was running at 5500 RPM’s and I was running 45 – 47 MPH. I was down at Lake Pepin Sunday and noticed that my RPM gauge was back to normal running at 6000 RPM’s and I was back up to 51.8 MPH. Bad Gas, Bad Oil, or possibly some motor problems. Any help or advice on what to do.
I do not know why your rpms were down.
But water temp and air temp with effect your speeds.
Could have been bad gas.
Make sure you read your owners manual also. My 225 EFI requires 91 octane. Putting in cheaper gas (or having stale gas) in the tank will effect your power.
Good question. I have a similar issue with the 4-stroke Mercury on my pontoon. Last summer after changing props I was at 5600. Stayed there all summer. Last weekend on maiden voyage it goes to 6200. Spoke to dealer. No clue. Either tach went bad or ??? The only change I made was to put in synthetic oil when I changed it last fall. This is a 40hp bigfoot. I’ll sit on it a while and see if it changes. If not I need my old prop back. Hauls pretty good for a 40!
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