Yamaha 3hp 2 stroke - conflict of info

[Eeyore]

I know this topic has been discussed before, but........there is a conflict of information in the manual regarding the fuel/oil mix. The manual that came with the engine (Yamaha 3A) states a 50:1 mix after running in. The exact same manual online states 100:1. I used to run my previous outboard (Yamaha 3hp Malta) with 100:1 and never had problems. This engine I've run with 50:1 for the last couple of years but I frequently have to clean the plug and carb out. What do the learned forumites think?

 

[TernVI]

I don't think 50:1 should cause plug problems, unless you do a lot of slow short trips.
Are you using the correct NGK plug?

 

[jwilson]

50:1 lubricates the engine bores and bearings better but prolonged low-rev running will oil up plugs more. Some outboards were originally sold as 100:1 models, but with a recommendation of 50:1 for heavy usage.

 

[VicS]

I know this topic has been discussed before, but........there is a conflict of information in the manual regarding the fuel/oil mix. The manual that came with the engine (Yamaha 3A) states a 50:1 mix after running in. The exact same manual online states 100:1. I used to run my previous outboard (Yamaha 3hp Malta) with 100:1 and never had problems. This engine I've run with 50:1 for the last couple of years but I frequently have to clean the plug and carb out. What do the learned forumites think?

You are presumably using an NGK grade 6 plug , not a cooler grade 7 plug , and a good TC-W3 certified 2 stroke outboard oil?
If all else fails you could try a grade 5 plug as used in 2 hp models

Have you checked the float level

Have you tried adjusting the carb low speed mixture .
(Reduce the ide speed to the absolute minimum, lean out the mixture until if falters then enrich it again to just run smoothly. Finally readjust the speed)

You could try a 75:1 fuel mix

If you can find it you could try Amsoil synthetic 2 stroke outboard engine oil at 100:1 ( I'd either fog it or run a tank ful of 50:1 before laying up whatever oil I used at 100:1)

Specifically designed for outboard motors, Outboard 100:1 Pre-Mix Synthetic 2-Stroke Oil contains a heavy dose of low-temperature dispersant additives that excel at reducing varnish, carbon and deposit formation in water-cooled motors. Its low-smoke, low-odor, low-toxicity properties produce fewer emissions at 100:1 mix ratios than oils mixed at 50:1, benefitting operators and the environment. Outboard Synthetic 2-Stroke Oil is formulated to prevent "oil loading" and plug fouling for rapid throttle response, making it ideal for trolling motors.

AMSOIL Synthetic 2-Stroke Oil has been providing improved performance and protection in two-stroke engines since 1973. Trust the extensive experience of AMSOIL, The First in Synthetics®, to do the best job protecting your engine.

Engine Protection
Outboard Synthetic 2-Stroke Oil provides premium protection and performance at 100:1 mix ratios. It is formulated for hot-operating two-stroke outboard motors, effectively fighting carbon and deposit formation and preventing ring sticking.

Smokeless Operation
Outboard Synthetic 2-Stroke oil's synthetic formulation burns cleanly. When mixed at 100:1, smoke is virtually undetectable. Boaters subjected to smoke and fumes benefit from these low-emission properties.

• Excellent lubricity and cleanliness properties
• Controls friction and helps prevent wear, plug fouling, ring sticking and exhaust port blocking
• Improves throttle response
• Lowers or eliminates smoke
• Delivers outstanding protection and performance at lean mix ratios
• Anti-rust formulation counteracts the damp environments often encountered in outboard applications

APPLICATIONS
For pre-mix use in two-stroke outboard motors, personal watercraft and jet boats that specify TC-W3. For maximum performance, mix with gasoline at 100:1 regardless of the mix ratio specified for the equipment. Richer mix ratios may be used where desired.

 

[Eeyore]

Thanks to all who responded. I am in Borneo, so specific oils are not easily available. The plugs are supplied by a local Yamaha dealer in the capital. Yesterday, I cleaned the carb out again and today it is running as it should. Normally, it would be run hard for a few miles to various immigration points but for the last 6 months I admit it has been on slow runs - which may account for the rough running. I was thinking along the same lines as VicS and trying it with 75:1 mix. Adjusting the mixture, I usually raise the idle speed, then adjust the needle valve until it runs smoothly before lowering the idle speed again - unlike VicS says, however, I will try his recommended way. Thanks.

 

[QBhoy]

So just to clarify...is this also a Yamaha Malta ? In the U.K. and Europe these are called a Malta. Everywhere else they are badged a 3hp. The original were all 100-1 mix. But it perhaps might be the case that you have a much later made commercial spec model. I’d think most guys will mix these things at 50-1 now. I mix all three of the Yamaha 2 strokes I have at 50-1...despite the original spec saying 100-1. Never had an issue with plugs fouling. Likely you will do better with a bit of carb adjustment

 

[Eeyore]

So just to clarify...is this also a Yamaha Malta ?

The engine looks identical and you are probably right about the locations. I had the Malta in the UK and I replaced it in Kota Kinabalu with the "3hp", so it's likely just a badging thing. I wonder why the hard copy of the manual differs from the pdf version downloaded from the internet?
Interestingly, my neighbour has a Yamaha 4hp which runs on 100:1 as per his manual.