Johnson Seahorse 7.5 Fuel Mixture

[Kimberly Ballas]

Im wondering what the Johnson recommended fuel mixture would be for my '79 Johnson 35hp outboard. Want to make sure I go with the manufacturers recommendations. Also, what 2-stroke outboard oil brand should I use? I've been doing some reading on this and a lot of people seem to be convinced that the Wally Mart brand is just the Quicksilver brand, relabeled.

I believe if you pull the cover on the motor you will see the rate.If it is a tiller they use to put a white sticker on the inside of the tiller handle with the rate also.50-1 rings a bell but I would not bet on it.

I've got an '81 Evinrude 35hp and it takes a 50:1 mix. I can't imagine it would have changed in 2 years. It does say the ratio under the cover as well so I would also check there as others have stated. Good luck

Thanks guys! I looked all over the outboard for the ratio and couldn't find it anywhere. After a lot of searching and talking to several people... it seems as if you are all right on the money... 50:1.

MERCURYs - ANY non-high performance Merc made after 1960 can handle a 50:1 mixture of fuel and oil. Racing motors will need more oil. I run 20:1 in my smaller Merc racers. Newer V6 high performance engines might need more and some require av-gas (100 octane).

Anyone who owns, or has owned, a two stroke outboard would have asked themselves the question; how much oil do I mix with my fuel? 100:1, 50:1 or 25:1? It is one of the most asked questions for those required to pre-mix their oil and fuel together. Below I have listed the oil ratios recommended by manufacturers and a few tips based on my experience.

100:1 - Mix 50ml of oil per 5ltrs of fuel. Recommended by Yamaha and Suzuki for most of their small two stroke engines up to about 30hp, this ratio requires the least amount of TCW3 two stroke oil. The result of using this ratio (less oil) is reduced spark plug fouling and less smoke. For older Suzuki outboards, pre-1997, I'd recommend running 50:1 as the information I've provided about is for current model two strokes.

Note: For commercial applications Suzuki recommends 50:1.

50:1 - Mix 100ml of oil per 5ltrs of fuel. Recommended by Mercury, Mariner, Tohatsu, Johnson and Evinrude this is my preferred ratio for all outboards including Yamaha and Suzuki. You can confidently use this ratio for any horse power and just about all year models. Whilst this ratio might see spark plugs fouling with extended use at lower RPM (such as trolling), in my opinion, it provides the best amount of lubrication for your outboard.

25:1 - Mix 200ml of oil per 5ltrs of fuel. This mixture is very rich and is usually recommended for running in brand new two stroke outboards and when running in rebuilt or reconditioned engines. If you have a rebuilt or reconditioned oil injected two stroke outboard (excluding Evinrude ETEC or Mercury Optimax) then you'll just need to add 50:1 to your fuel and let the oil injection system add the rest of the oil to make up the balance to get to 25:1. Most technicians will have their own opinion or view on how long you should run the 25:1 ratio for but, I always recommend between 8 and 10 hours. Unfortunately, you will foul plugs at this ratio and leave a very impressive smoke plume on engine start up but, outboards that have been rebuilt or reconditioned need this extra oil while the piston rings bed into the bores.

Oil ratios can be confusing and daunting. The last thing anyone wants to do is not use enough oil and damage their pride and joy. Hopefully, the above answers any questions you may have and gives you a better understanding of what ratio your outboard requires.

Shop for Penrite outboard oils & lubricants here.

Its a little bit messy but good for a first boat. Unfortunetly the motor needs some repairs but im not sure of the year model series. Could anyone tell me how to find this out? once i find this i can do some more research and hopefully get an owners manual to get the correct fuel and air mixtures.

I have a 35 Johnson Seahorse Ive had it for about 2 years its my first boat to. I have always used Shell 2 stroke marine oil and i mix 50-1 ratio that 100mls to every 5 litres and its been a great motor after i fixed the bodgy work from the previous owner which caused me to get reco gearbox and get proper linkages and it hasn`t missed a beat yet. touch wood.

Hi, if it is a 33HP that puts its age back in the 1960's and the fuel/oil ratio is 50:1 with good quality oil. Fuel/air ratio is a total different thing and is adjusted by the mixture screw in the carby and unless you know what you are doing I would not play around with this. An owners manual will not give you this ration and only a service manual would and you would not get one for that age. We might have one in the workshop that you could photocopy?

Any questions ask, because with a bit of maintance there is no reason the old girl can run for another 30 plus years. If my engine I would service the cycliner head making sure the thermo is in good working order, do a water pump service and grease/oil change and she will be good to go.

Sometimes there is a tiny leak in the fuel line, small, but big enough to suck air into the system, it causes a shortage of fuel supply to the carburetors because it sucks some air instead. double check all your connections and hoses. As for speed, that may be a trim issue. If you can, do a compression test and see if the cylinders are within 10 % of each other. As for the fuel pump. It may be that the membrane is eaten up by ethanol or just gone leaky because of old age. Membranes are cheap ,so is a $20 fuel pump. They usually are at least twice that price. If you decide to take the fuel pump apart to replace the membrane, be very careful with the tiny springs and places where they are in. The suspects are false air and pump membrane.

I just read your report again and the cracked fuel lines and the electric choke do point at a possible other cause. Fuel lines not only crack outside, but also inside and tiny rubber particles are swept along in the fuel towards the carburetor where they can cause trouble in 2 specific spots. The first is where the fuel comes into the bowl. That is where a little inlet control needle is held in place by the float. the second place is the high speed needle hole. I write this because the electric choke bypasses that whole setup of the carburetor and they enrich the fuel mixture straight into the horn of the carburetor.

I wonder what fixed the problem? Update please? Thanks. If you're still looking, try a portable gas tank and hose to eliminate the built in tank and hoses if applicable. Process of elimination is sometimes easiest way to troubleshoot.

Sent from my moto z3 using Lake Ontario United mobile app

If the problem was the plugs themselves would it run like H the first time he tried it out I don't know....? Seems more like fuel related (e.g. pump) or spark distribution problem....had that when the power pack was going bad on my 1979 Johnson 35 and thought it was fuel related...I don't know whether they used the "modular" power pack back in 1976.

We have the exact same year motor doing similar. Motor ran great until I forgot to open vent on a plastic tank causing it to collapse. After that it would bog down under a load and not plane out. We changed plugs, power packs, seafoam thru carbs and replaced fuel line to tank, still bogs down. Any other Ideas?

3a8082e126