Fuel:Oil Ratio

[Fishcamp]

I recently aquired a 1954 Johnson Sea Horse 10Hp motor (Model# QD-15). The motor, which uses a 24:1 fuel il ratio, runs great, but the exhaust leaves a minor oil slick when the engine is running at idle in neutral. With today's new oils, can I go to a 50:1 ratio? Has anyone actually run an old motor designed for a 24:1 ratio at higher ratios? I've had some feedback from some other postings saying it's no problem with the new oils, but I'd sure like to hear from someone who has ACTUALLY done it!<br />Any feedback would be greatly appreciated.<br />Thanks!<br />Fishcamp

 

[Trent]

Re: Fuel:Oil Ratio

Iv done it for years on my grandfathers 1955 Johnson 5hp that was given to me with no problems.

 

[JB]

Re: Fuel:Oil Ratio

Risky. You have sleeve bearings on the top of the rods. I wouldn't risk it.<br /><br />Red sky at night. . .<br />JB

 

[Pursuit2150]

Re: Fuel:Oil Ratio

Stick with the ratio called for. You may have to clean the carb and plugs more often. Spend the money on oil or spend the money on repair.

 

[DJ]

Re: Fuel:Oil Ratio

I've done it on my 58 7 1/2. I didn't quite go to 50:1. Sort of split the difference at about 40:1.<br /><br />JB's right, you're taking a risk, but I don't think it's a great one.

 

[Pursuit2150]

Re: Fuel:Oil Ratio

Just Curious** Why would any one want to modify the recommendations given in the specs??

 

[Lark40]

Re: Fuel:Oil Ratio

This is probably one of the most debated issues with pre-1965 OMC engines.<br /><br />Sure, you think, oils have greatly improved in 50 years. But, so have engine internal tolerances. Your engine was built expecting to have a lot of 30 weight oil handle its sleeves and other internal tolerances.<br /><br />It would be nice to be more environment friendly, but I won't chance running my Lark on other than 24:1 mix.

 

[D.J. Diver]

Re: Fuel:Oil Ratio

I have a 1958 Johnson 10 HP (model QD-19.When I aquired it in 1993 I asked a local marine shop what ratio to use.They said 50:1.So I bought OMC TCW-3 oil and that's what I mixed it at, and have ever since.I haven't had any problems at all and she still runs like a champ.A few months ago I submitted a post asking if small outboards were designed to run continuosly at full throttle,since that's pretty much how I use mine.One reply to that post informed me that the internals of the powerhead have bronze babbitt bushings that need extra oil.I'm pretty sure he wasn't the only one that cringed when he read I've been mixing at 50:1.I thought about mixing richer after I read all the reply's but was concerned about fouling plugs.I recently had the power and cylinder head off and everything looked great.Of course I couldn't see the crank and rod bearings.You should probably play it safe and experiment with richer mixtures and find one that strikes a good balance.I don't have to worry about it anymore.I 've got myself a brand new Mercury 25HP and I LOVE it! No more having to use full throttle to get anywhere.Good luck with your motor.

 

[petryshyn]

Re: Fuel:Oil Ratio

I have a 1954 5.5hp Johnson. <br /><br />I've tried 100:1 with synthetic, 50:1 with tcw-3, and 24:1 with sae30<br /><br />I used 100:1 and found the crankcase bearing area extremely hot at idle, but it ran...Who can say what mixture is hurting there engine until they run it for years and disassemble it for inspection. Just because it runs, doesn't mean it'll last as long as it should...<br /><br />My advice (for what its worth) is to mix 24:1 TCW-3 if you are mostly idling or just off idle. Very little volume of pre-mix at idle needs a richer mixture. If you are using it mostly at WOT, go 50:1 TCW-3. The extra volume will keep the friction bearing happy.<br /><br />If you want to be safe, and don't know who to believe, always go with OEM.....<br /><br />my .02 cents worth.....

 

[jimfishes]

Re: Fuel:Oil Ratio

Our local marina,who is also a large Johnson dealer, sells only 50:1 at their docks. They only ask one question: Was your motor recently rebuilt, thus having tighter tolerances on crank and pistons? So, for the last ten years I have used TCW3 @50:1 on all my motors with absolutely no problems, BUT the largest of these is 15hp, and vary from '58 to '98, all OMC.<br />As an aside, I have found that Champion makes<br />lousy spark plugs for small engines, Autolites are twice as good, and AC is 3 to 4 times as good.<br />----jim----<br /><br />Just my tuppence!