25 four stroke tune up/service list?

[Blake]

I've got a '02 25 hp four stroke Yamaha that I haven't serviced in a couple years, and I've forgotten what all I need to do to give it a proper tune up.

I'll be de-carbing through the air intake, changing the oil and filter, new spark plugs, changing the lower unit oil, possibly a new water pump. What am I missing? Do I need to bother with new plug wires or any other ignition parts? What about timing, is that something that needs to be reset on those motors? Is there a fuel filter under the cover?

Any help would be greatly appreciated.

 

[cgaengineer]

Change the plug, engine oil and lower unit oil...don't waste your time on the rest.

The water pump might need to be changed as well, depends on the hours.

 

[stevesecotec02]

If its never been done you might want to change the thermostat.

 

[turbotodd]

Water pump for sure. Impeller probably has a memory by now. Also the metal sleeve is usually worn a little; I like to replace it as well. Thermostat is not a bad idea. Mine was stuck open and it would "make oil" because the engine never got hot enough. New one solved that. Lower unit oil is a must as is the engine oil and filter. Spark plugs are a good idea too and don't forget about the fuel filter if you have one. I like to clean the carb too; but if yours is running great and doesn't sit more than a couple weeks at a time, it may be ok. Also a valve adjustment if it's not been done since 2002. Mine were a little tight on the intake and loose on the exhaust. Set them back to factory specifications and it purrs like a brand new motor again.

The valve adjustment is easy, BTW. Remove voltage regulator and ignition coil, then tilt the motor up. Remove valve cover with 4 6mm bolts. From there it's just a normal rocker-arm adjuster style 4 stroke, like a 4 wheeler or tractor. TDC compression stroke, measure, adjust. I think lots of people forget the valve adjustment.

Decarb isn't required as these little engines don't carbon up real bad. I just usually run some ringfree through the fuel every tank. Last time I had the borescope out, I had a looksee and it looked literally almost brand new inside. Top of pistons still shiny and not all blacked. Intake valves do get dirtier but ringfree also helps that too.