’57 Evinrude 7.5 fleetwin fuel mix

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    jeff-register

    US Member - 1 Year
    Replies: 1154
    Topics: 48
    #194285

    Frank,
    I agree with you but must confess my Fastwin 15 was run on a plowing, not planing hull so 50% throttle was the most ever used. I was using Pennzoil 2 stroke mix back in 78 or 79. That motor ran so well!! Great memory’s!!

    Tubs
    Tubs

    US Member - 1 Year
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    Topics: 155
    #194326

    Mumbles
    Mumbles

    Canada Member - 2 Years
    Replies: 4337
    Topics: 428
    #194333

    I have the same chart Tubs has posted but I totally ignore the OMC recommended 24:1 mix given for the earlier AD and CD motors and stick with the original 16:1 mix for the older models. The 50:1 mix for the ’64 and later motors is OK as they all had needle bearings on the rod.

    Notice to they say ’50:1 mix can be substituted for 24:1 mix as long as Johnson oil is used’. Was it possible the powers that be at OMC realised that sales of new six horse motors weren’t as good as expected and lots of their older motors were still being used regularly with no end in sight? Realising that a satisfied Johnson customer would probably come back and buy a new one again, slowly but surely eliminating the old motors off the face of the earth by purposefully and deceitfully shortening their life span would guarantee increased sales and profits and everything would be peachy keen again. After all, why wouldn’t they recommend the same 24 or 50:1 mix for the old TN series of motors? Possibly because they knew they would need replacing soon anyway or new parts for them were just NLA from their dealers.

    Possibly I’m a bit too suspicious but I do have a box full of badly scored pistons I’ve collected over the years and the majority of them are from the 5.5 and six horse lineup. Sure, their are other causes but I also have a Fleetwin 7.5 crank and rod sitting here with close to an 1/8″ clearance on the lower rod journal. The rest of the motor was pretty worn to and I suspect it was caused by using a too light gas/oil mix.

    As for the original question, stick with the recommended 16:1 mix and enjoy your summer! After all, oil is the lifeblood of any motor and is the cheapest thing you can put in it. Trying to save a few pennies now might cost big dollars later. Don’t be stingy with the oil as too much is always better than not enough!

    • This reply was modified 1 week, 3 days ago by MumblesMumbles.
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    fleetwin

    US Member - 2 Years
    Replies: 2868
    Topics: 37
    #194370

    No fight or argument here – I do understand and have read the many, many posts here on fuel mixes, in general, and I’m not looking for a recommendation on that.
    I only wanted to know if anyone knew WHY the factory specified that particular motor for 16:1, when the others in that same list called for 24:1.
    What was different about the 7.5.?

    The reason why the 7.5hp is singled out is because of the plain bronze bushings on the connecting rods….The 5.5 and 3hp models are set up the same way….

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    billw

    US Member - 2 Years
    Replies: 1106
    Topics: 38
    #194417

    When I was a kid, I took a perfectly good-running ’56 Fleetwin, hooked up a tank of 50:1 EVINRUDE oil mix to it, at the recommendation of a professional O/B tech, and went about 1000 feet at WOT, before it threw a rod. Maybe if I had used JOHNSON oil, it would have been okay? I don’t think so.

    Long live American manufacturing!

    frankr
    frankr

    US Member - 1 Year
    Replies: 4715
    Topics: 47
    #194431

    I am totally convinced that those dumped rods in 5.5 and 7.5 motors are the result of water getting into the crankcase through a faulty lower seal, not because of lack of oil. Now, might have an abundance of oil prevented the water damage? Good question.

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    crosbyman

    Canada Member - 1 Year
    Replies: 1401
    Topics: 181
    #194433

    better to burn oil instead of burning up a motor …they say 🙂 .

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    billw

    US Member - 2 Years
    Replies: 1106
    Topics: 38
    #194512

    I am totally convinced that those dumped rods in 5.5 and 7.5 motors are the result of water getting into the crankcase through a faulty lower seal, not because of lack of oil. Now, might have an abundance of oil prevented the water damage? Good question.

    I had beginners luck: When this rod let go, it didn’t go through the crank case. My Dad and I took it apart. He looked it over with his aircraft mechanic’s eye. We bought one rod and some gaskets, put it back together and it ran the entire next summer on 16:1, usually either at dead idle or WOT, on an 8′ Mini-Max.

    Edit: It was a very long time ago; but it could very well have been the bottom rod that let go; so I see your point.

    Long live American manufacturing!

    • This reply was modified 1 week, 1 day ago by Avatarbillw.
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    jeff-register

    US Member - 1 Year
    Replies: 1154
    Topics: 48
    #194530

    Can someone tell me about my 53 Evinrude 15 on the rods weather or not they had needles or not? I’m thinking they did but not sure. Asking why the inside the cowl, it stated ” for convenience mix 1 qt in a 5 gallon container. Result was 19 qts of gas to 1 qt of oil.
    Anyone know? Needles or bushings?
    Always run my 78 Evinrude 85 @ 40/1 ratio. Heard the rings are close to the crown of the piston.

    David Bartlett
    David Bartlett

    US Member - 1 Year
    Replies: 248
    Topics: 13
    #194533

    Can someone tell me about my 53 Evinrude 15 on the rods weather or not they had needles or not? I’m thinking they did but not sure. Asking why the inside the cowl, it stated ” for convenience mix 1 qt in a 5 gallon container. Result was 19 qts of gas to 1 qt of oil.
    Anyone know? Needles or bushings?
    Always run my 78 Evinrude 85 @ 40/1 ratio. Heard the rings are close to the crown of the piston.

    Jeff,

    That motor has needles on the crankshaft end of the rod.

    David Bartlett
    Pine Tree Boating Club Chapter

    "I don't fully understand everything I know!"

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    fleetwin

    US Member - 2 Years
    Replies: 2868
    Topics: 37
    #194566

    When I was a kid, I took a perfectly good-running ’56 Fleetwin, hooked up a tank of 50:1 EVINRUDE oil mix to it, at the recommendation of a professional O/B tech, and went about 1000 feet at WOT, before it threw a rod. Maybe if I had used JOHNSON oil, it would have been okay? I don’t think so.

    Don’t feel bad, OMC sure pushed a lot of “hype” when it came to the capabilities of new and improved oils…. I remember this malarkey being pushed on us by the instructors at service school as well…. I’m convinced most of the engineers had never even seen a 56 Fleetwin, much less worked on them or run them… I always felt that engineers should take an OMC engineering history course every year….Just seems like the same mistakes were repeated again and again, even though past failures should have been a good lesson……
    I guess half the problem is that none of the folks that new the history were still around to teach the course!
    The other half of the problem is that the sales/cost departments ruled the place, so engineering designs were often squashed due to cost or going against that sales department…

    • This reply was modified 1 week ago by Avatarfleetwin. Reason: addition
    Mumbles
    Mumbles

    Canada Member - 2 Years
    Replies: 4337
    Topics: 428
    #194579

    Here’s what happens if you run a 5.5 or 7.5 horse motor with not enough oil in the mix and out of the water. No, I do not know who these axxxxxxs are.

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    jeff-register

    US Member - 1 Year
    Replies: 1154
    Topics: 48
    #194582

    thank you Don!
    It was that way at TRW building pipe bombs….or air bags. They wanted us to perform service on the robotic assembly lines running & dealing with explosives. Big meeting with all the staff. I made a few negative remarks about reality check & “show me how you change oil at 65 mph & I’ll follow your lead. The passenger air bag had a 2.5” aluminum pipe packed with explosives. Just to be in the same room with sodium azide was toxic. The robots scrapped too many sodium azide pellets so TRW put people in there to use all the scrapped pellets up.
    TRW = terrible risky work!!!!

    Thanks for the data on my 53 Evinrude 15. Now I know why the cowl said 1 qt of oil to 5 gallons of fuel!
    Sorry guys I was wrong!!

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    bwanadon

    US Member - 1 Year
    Replies: 7
    Topics: 2
    #194612

    I vote 16:1. I have the manual in front of me. Now oil back then and oil today are different. Err on the side of caution, use 16:1. More oil will not hurt anything.

    I have that exact motor. Every time I work on it it runs worse.It’s ripping my heart on and chewing it up. It’s down on my workbench pulled apart once again. I’m going to hone it and put rings in it. If I can get the bolts out of the power head. Well not if but when. I’ve got a Bridgeport mill at work that says those bolts are coming out.

    If you need, I’ve got the owners manual and parts manual. These guys around here are experts, they will give you good advice. Good luck I hear these are excellent motors that run great.

    Don

    Mumbles
    Mumbles

    Canada Member - 2 Years
    Replies: 4337
    Topics: 428
    #194639

    Here’s the ’56 Fleetwin parts manual in PDF form for everyone to enjoy.

    Evinrude-Fleetwin-7.5-HP-1956-Parts-Manual

    I can’t find a ’56 Fleetwin owners manual but a ’56 Johnson AD owners manual will be close enough.

    1956-Johnson7.5HP-AD10-AD-Owners

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