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greenwormguru
20-03-2009, 11:15 AM
hi guys,i recently brought a 2nd hand tinny with a 30hp 2stroke yammy,it states to mix fuel at 100 to 1,some people have advised me to make it richer as they think its to lean!i do a fair bit of trolling with it.should i run it as it states or what?cheers gwg:-/

johno r
20-03-2009, 11:48 AM
run it at 100;1 as that is whot yamaha state . I have 30hp 3cyl and run it at 100;1 with no props at all any more and she will smoke when trolling

cormorant
20-03-2009, 11:52 AM
Use good quality oil not cheap and nasty if running that ratio

FNQCairns
20-03-2009, 11:53 AM
Strictly you can but stick with the yamaha oil at least, 100:1 is fine for trolling etc if it where my engine no way would I run at cruising speed on 100:1. The recommendation stem from 2 things, first was the 3 piston ring setup they used to have, 50:1 used to carbon up the rings and they would crack/catch a port...keep in mind not everyone treat outboards the same ie propping to lug, the 100:1 idea was the lesser of 2 evils, redesign/fix all and existing engines, or put it onto the customer down the line and out of warranty.
2 is it's good marketing all round.

I understand they over time updated the engine to a 2 ring piston but kept the marketing as the % of in warranty problems from 100:1 made it worth their while, longevity is entirely out of warrenty you understand.

Personally I would choose 75:1 out of warranty with a known good oil and keep WOT periods short, still i wouldn't be unduly worried about 50:1 either but would leave the 100:1 for those who do not plan to keep the engine for LOTS of hours under recreational use.

cheers fnq

boys play
20-03-2009, 12:05 PM
Found myself with the same dilemma recently...bought an old tinny with a 6 hp Evinrude. The ratio is labelled on the side of the motor as 100:1 which I thought was to lean for an old motor. Looked up various web sites for similar concerns, and the flow seems to go with a 50:1 mix, particularly if the motor is old. Interesting comment on the carbon..hope that is not the case.
I spent a few hours trolling at dead slow speed last w/end after bass..plugs inevitably oiled up after a while and smoked a bit, however a bit of faster running seemed to clear the passages.
My vote is to have an oilier mix..perhaps 75:1 is a good compromise?
cheers
Ian

BaitThrower
20-03-2009, 12:07 PM
Mate I just picked up a 30Hp Yamaha CV second hand... 2002 model. It too states 100:1 but I think I am going to run it at about 70:1, maybe even 65:1 and see how it goes... I imagine I will do 50:50 trolling/cruising so i think 100:1 is a bit too lean for anything but trolling or low rev displacement running.

cormorant
20-03-2009, 12:24 PM
If you run lower ratios you may see some benefit from using products like carbon guard or semi-syntheic oils that have low residue . You should also run a spray of engine tuned to release the carbon and sticky rings every now and then and it will last ages.