I was looking for advice on a general tune up. I started my 2004 yamaha 75hp four stroke today for the first time this spring and it was acting like it was missing. I think it’s time for new spark plugs, and a water pump. just wondering if anyone has ever done it and if it was something I can take on myself or if I should take it somewhere. 
http://www.repairmanual.com/marine/4
Worked on my ’00 Honda 40hp 4 stroke most of the afternoon on Sunday. R&Red oil, oil filter, fuel filter, and water pump. Adjusted the valves and sync’ed the carbs. (this you will need a bank of vacuum gauges for the # of cyls. you have) My best suggestion is to first find a manual specific to your engine. Other than that it was a piece of cake ! ! ! 
P.S. the web site at the beginning of this message is a good source for that manual…… GOOD LUCK ! !
How many hours do you have on it? I’m guessing some new fuel and a can of SeaFoam will work wonders. As for the plugs, pretty easy to pull them and see how they look. Had my “01” F80 in last fall for a seal fix and asked about doing the water pump. The mechanic said with the Yamaha’s if they are pumping a good stream don’t worry about it. If they go bad you’ll see it. Just some thoughts for you.
I’ve only got about fifty hours on it since I bought it 4yrs ago, but it was used. I put an hour meter on it when I bought it. Looks as though the water pump had been changed once before. I was just having some concerns with my water flow at the pee hole and thought this might be the problem. Besides, I like to have my gear running in top shape. I’ve been stranded before in a friends boat and it was NOT 
fun……
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