Yamaha 4-stroke engine oil

[hoavannguyen]

I need some advice from some experts in the forum on engine oil for Yamaha 4-stroke engine. I am currently living in Guam and the weather here is hot all year round. I am spending 10-15 hours in the water running hard or throlling for several hours. From the manual, the recommended engine oil is either 10W30 or 10W40, but my mechanic suggest changing to 20W50 or 25W40 for higher viscosity since the weather is hot here all year round. He said that it will keep the engine running cooler. I would appreciate any thoughts/comments from the forum.<br />Thank you,<br />Hoa

 

[seahorse5]

Re: Yamaha 4-stroke engine oil

Actually a "thicker" oil will generate more internal heat in a motor due to the extra "power" needed to pump it. Stick with the factory recommended oil for best results. Most Yamahas have water circulating by the oil sump to help keep the oil temperatures low.<br /><br />If you can find it, get the March issue of Bass and Walleye Boats magazine for an article and test on different outboard and car oils for 4-strokes.

 

[rodbolt]

Re: Yamaha 4-stroke engine oil

the 10w30 10w40 is fine. I like an additive like stor-n-start for added corrosion protection.<br /> save the extra money for water pumps pressure valves and t-stats. keep them good and change them every 250 hours.<br /> good luck and keep posting

 

[BillP]

Re: Yamaha 4-stroke engine oil

Ditto what seahose says about running hotter. Cycle Mag had a test several years ago on aircooled mcy engines and various oils. They used a dyno, egts and chts to measure. Motors specified for 10-30 were run on heavier oils. The 20-50 "racing" oils ran the motors on the edge of "too" hot. Water cooled engines probably suffer too. Another good reason why following the mfgs specs are best.<br /><br />I have a 50hp 4 stroke and changed oil from 5-30 to heavier 10-40 for better corossion resistance during storage. Both are speced in the owners manual.