Trying again. I entered this post yesterday (or was it the day before?) and I can't find it. Now, I'm trying again. Can anyone out there help me find what the fuel/oil ratio is for this old '61 Merc 500 50 HP engine I've gotten along with the boat and trailer I bought? Also, really would like to find an owner's manual for this motor.
Original mix was 24:1, I am not sure, but I think with the new TC3 W oils or better you can run 50:1. As for a manual, you need the 1965 and older manual. You can also buy then on CD on E-bay.
I have a 63 that I've been running on 32:1, and its safe. I'm going to see if it likes 40:1 better, but I read that because of the bearings it needs richer fuel, yet most people suggest 50:1.
I like to be safe then sorry. It doesn't smoke at 32:1, so I'm in no rush to try 50:1.
The new oils are nice in the lack of smoke. I run my older Johnnyrudes on 50:1 now, but there lower HPs, 28 and under. My newly aquired mrec 1961 800, I'll run for a while at 24:1, but I'll most likely move to 50:1 at some point
Any of the larger Mercs are quite happy at 50:1. They all are "fully jeweled" meaning every bearing surface has a ball bearing, roller, or needle on it. No bushings allowed. Years ago I ran all manner of late 50's and early 60's Mercs on 50:1 with no ill effect.
In deference to their age, however, 40:1 ain't gonna hurt anything! Just be sure to use a quality oil, either a major outboard mfr's or good aftermarket. I've been using Penzoil Synthetic Blend and it seems to work very well and isn't too smoky even with higher oil mixes. Also avoid Gasohol if possible.
Along with a richer oil mix you should use a decarbonizing fuel treatment such as Seafoam, Berryman's B-12, Chevron Techron, or any of the outboard mfr's such as Yamaha Ring-Free, OMC Carbon-Guard, etc. This'll keep the rings carbon-free and non-sticking.
BTW on the old JohnRudes, you do have to be careful as some of the smaller 50's motors (and a few early 60's) do have babbitt or bushings as bearing surfaces. These require mixes close to the original recommendations to keep things well-oiled.
Some of the more 'modern' 50's motors needing a rich oil mix would include 5.5 & 7.5 hp, which are all babbitt/bushed. Definitely do your research on others because some have needle or roller bearings on the crankshaft but bushed wristpins and these would also need a heavier mix. Should be no problem with a 28Hp though.
If I recall the older 15's had bushed wristpins and maybe some 18's but that's best left to the JohnnyRude forum!
I think the Mercs of that period that are labelled "Fully Jeweled" on the cowl are good for 50:1, they have no sleeve bearings. Without that label I would run 24:1.
We need an old timer Merc-spert to clear this one up.
lol
I don't want to flood a merc forum with johnyrudes, but I am ok on the 28 and the 1964 20, I have a 1956 7.5 which I am running 40:1, since I am not sure of the bearings,(pretty sure 50:1 would be fine, but 40:1 don't smoke much anyhow) as well I have a clinton j7 which I run 32;1.
The 61 800 FGs is my first merc, I've been on the learning curve trying to get everything set up. Its sat for about 35 years, in a showroom, so I've been trying to get it ready to run. I thought since its sat so long, maybe I should stick with the orginal mix, for the first few tanks. Its been seafoamed, and deepcreeped already, just got the throttle/shifter hooked up, and set up.
I did the waterpump, and just have to do the link and sync, then I'll see how it runs. (this weekend if I get the time)
JB, I read a post by "clams" about the fuel mixture being ok at 50:1 for the older mercs, but I am not 110% sure if there were ages and exceptions in the post.
Be nice if someone could clear up the doubt.
Thanks for all your advice. I found a number in the paperwork with the title. It is 2629260. Not sure if that is a serial number or what. Does anyone know what I'm dealing with here? Is it possible that I have the wrong year?
Well now that I can be sure my 63' 50 hp, 500 will be safe with 50:1, I'll mix a tank up and see. It does miss once in awhile while idling, sometimes stalling the motor, but it always starts right away.
Thanks for the Seafoam and other tips. I'm gonna grab some of it once I can. I grabbed some engine tune-up/carb cleaner (spay can), from a merc dealer, and I've used it every year. your supposed to use the whole can, but I only use half.
1961 Mercury 500 (50 HP) oil/gas ratio?
Linear Mode
