1998 25 hp Yamaha Oil/gas

[bag007]

Hi all
I know this question has probabily been asked but I cant find it.....
what is the oil to gas ratio. I bought a boat with the motor ... 1998 Yamaha MSHX 25hp. The previous owner was runing 50:1. He said he preferes to run all his motors like that. But On the side of the motor there is a sticker saying 100:1... I was thinking running at 50:1 might foul the plugs quicker .. be a little more smokey but is it better for the Engine??
Thanks for your replies in advance ..
TONY

 

[trendsetter240]

Re: 1998 25 hp Yamaha Oil/gas

50:1 is the correct fuel/oil mixture.

 

[trendsetter240]

Re: 1998 25 hp Yamaha Oil/gas

Sorry, let me expand on that. 50:1 will provide the lubrication that the engine needs.

I had a mid 80's Johnson 30hp that had the 100:1 oil mix sticker on it. OMC issued a service notice to run these engines at 50:1. What they found was that 100:1 would not leave enough oil on the engine internal parts to prevent damage.

 

[bag007]

Re: 1998 25 hp Yamaha Oil/gas

Thank you so much for your prompt reply. I definately wil go with 50:1
TONY

 

[rodbolt]

Re: 1998 25 hp Yamaha Oil/gas

not quite correct on that OMC bulliten.
the bulliten stated basically that while 100to 1 provided adequate lubrication for running it was inadequate to proted the shiny parts inside the engine and rust and corrosion could form in as little as 30 days,
yamaha hasnt said anything but metal is metal.
if you maintain the cooling and fuel system in a like new condition and follow the reccomendations for long term storage(anything over 30 days) 100 to 1 will work.
I personnaly reccomend 50 to 1 and still following the owners manual for long term storage.
wont foul plugs any faster or slower.

 

[bag007]

Re: 1998 25 hp Yamaha Oil/gas

Rodbolt. I am going to follow your advice... and run 50:1 I am greatful for your advice. Thank you for your updates to!
TONY

 

[ttp]

Re: 1998 25 hp Yamaha Oil/gas

You are all talking about petroleum bases oil, 50 to 1. Not the synthetics, right? The synthetics are becoming very popular and can be mix at a thinner ratio, right?

 

[JimS123]

Re: 1998 25 hp Yamaha Oil/gas

Some good info here, some questionable.

The truth is that some years back when the riceburners came out advertising 100:1, to stay with the competition OMC recommended the same. Then, they had a few engine failures that they attributed to low oil so they issued the subject bulletin.

Many of the gurus on this web site recommend 50:1. My local dealer (who has been a Yami dealer since day one, and an Evinrude dealer since the 1940's) told me that 100:1 is adequate in Yamis based on his experience. He's a master tech for all outboards.

I tried 50:1 in my Yami and it smokes terrible. 100:1 runs fine and there is a good coating of oil on the plugs. I compromised on 75:1 and I still get some smoking and some fouling.

 

[trendsetter240]

Re: 1998 25 hp Yamaha Oil/gas

Some good info here, some questionable.

The truth is that some years back when the riceburners came out advertising 100:1, to stay with the competition OMC recommended the same. Then, they had a few engine failures that they attributed to low oil so they issued the subject bulletin.

Many of the gurus on this web site recommend 50:1. My local dealer (who has been a Yami dealer since day one, and an Evinrude dealer since the 1940's) told me that 100:1 is adequate in Yamis based on his experience. He's a master tech for all outboards.

I tried 50:1 in my Yami and it smokes terrible. 100:1 runs fine and there is a good coating of oil on the plugs. I compromised on 75:1 and I still get some smoking and some fouling.

I've seen this debated many times. it always seems to end up that OMCs go with 50:1 and Yamaha is ok at 100:1 WHEN recommended for a specific motor.

My statement, is personal experience, that I have run outboards that had the 100:1 sticker at 50:1 without problem. Never had a problem with fouled plugs nor did I experience premature wear on internal engine parts.

What is different about these motors that would make it ok for them to run a 100:1 mix? On the other hand, the excess smoke could be from an overly rich mix at the carb and not directly caused by the 50:1 mix.

Again, I'm stating personal opinion based upon what I've experienced and read on this issue.

Cheers!

 

[JimS123]

Re: 1998 25 hp Yamaha Oil/gas

I also stated my personal experience with fouling. My comment about OMC engine failures came from an OMC insider that worked for the company in a technical capacity for 40+ years.

 

[robert graham]

Re: 1998 25 hp Yamaha Oil/gas

I've used the 50:1 oil mix for 20+ years in all motors(mostly Yamaha) with no fouling/smoke issues, did switch to the Pennzoil 100% Synthetic Outboard motor oil a few years ago and seems to burn even cleaner with very little smoke. Recommend Ringfree and Stabil Marine all the time with a fuel/water seperator. Good Luck!

 

[bag007]

Re: 1998 25 hp Yamaha Oil/gas

Hi all Thanks for your input. I have used the motor with 50:1 using penzoil and it runs well with no smoking issues and I checked the plugs and wow they are nice and clean.
Thanks again !!
TONY