20 hp Yamaha questions

[mmd5]

I picked up a 1991 Yamaha 20hp 2-stroke(model 20 MLHO) on the weekend. It was fogged and gas stabiliser was ran through it when it was 'winterised', but had not been running for 4-5 years. It was purchased in 1996 and has less than 10 hours of service. To my surprise it started almost right away and once it warmed up it would idle down very nicely. I ran a 50:1 mix through on start up although it calls for 100:1. I am going to change the lower case oil, plugs, and fuel filter. Is there anything else I should be looking into such as having the carbs cleaned?. I'm going to continue to use the Yamaha recommended premix oil, but are there any suggestions on the 100:1 mix. Should I possible run 75:1 or something more conservative?. The unit will be used a 16' open hull aluminium, mostly for fishing, so low trolling speeds are desirable. <br /><br />Thanks in advance, look forward to your suggestions and comments.

 

[JB]

Re: 20 hp Yamaha questions

Howdy, MMD5.<br /><br />Yamaha withdrew their recommendations for 100:1 and now recommend 50:1 mix.<br /><br />You probably should replace the water pump impeller. They have a finite life, whether in use or just sitting.<br /><br />Any TCW-3 rated oil will do fine. I used (when I had 2 stroke engines) Wal-Mart's SuperTech at a much lower price than "premium" brands. There you don't have to pay for the brand name and the advertizing. There is no hard evidence that your engine will run better or last longer with a different name and price on the oil bottle, as long as it is rated TCW-3. Any additives that matter are sold seperately.<br /><br />Sounds like you have an excellent engine for your boat.<br /><br />Good luck.