1977-85hp Evinrude Carburetor adjustment screws

[John Drew]

Where are the carburetor adjustment screws located on a 1977-85hp Evinrude?

Most I have seen in the past are brass. I don't see any brass screws on any of the four.

Is it under the screw in the attached picture?

 

[crb478]

Re: 1977-85hp Evinrude Carburetor adjustment screws

The jets are fixed size and not adjustable

 

[John Drew]

Re: 1977-85hp Evinrude Carburetor adjustment screws

That explains why the brass screws, under the cap screws, were seated at the bottom. I had to re-shape a screwdriver to fit the head and removed them.
Is it common for these to need replacing? I have the carburetors off and going to clean and rebuild. Should these adj screws be replaced? The overall condition of the carbs are good. no gum any where.

The problem with the motor is that it misses alot.
Things I have done:
1. Put 10 gal of new gas in with Seafoam and Stilbilt . I could not get the old gas out. Been in there since 4 July last year, the previous ower said.
2. Put in new spark plugs. The old ones had a lot of carbon on them.
3. Replaced the fuel pump after I broke the nipple off the old one trying to remove the hose so I could replace it. Urrrrr!
4. Let it run for about 15 min with water mufflers on. Seems to run better at faster speeds and misses at lower speed.
5. Sprayed Seafoam into the sparkplug cylinders and into the carberator- air intake
6. The previous ower said it was rebuilt about 4 years ago when they ran it without oil and was only used at company picknick 4 July. It has 110 written on the two right clyinders and 115 on the two left.
7. At the sparkplug, the metal stays cool to the touch after the 15min run.
8 I did notice, at the needle on the carb, the little spring which attaches to the float was missing.
9. At the moment, this was only on the top carb. I have not gotten to the bottom one yet.

 

[emdsapmgr]

Re: 1977-85hp Evinrude Carburetor adjustment screws

Those "brass screws" were the set high speed jets. They do take a special screwdriver to get them out. They are marked on the side with the size of the jet. Those were put in at the factory to exactly meter fuel for those carbs. (The idle jets are also fixed on that engine.) A normal boat owner will not need to change them, but removal for inspection and cleaning is a good idea. Make sure you use some type of carb cleaner on the passages inside the carb bodys. An aerosol Gumout product works well. I'm not a fan of using old fuel, esp that which is a year old. It is probably stale and the ethanol in it may have attracted water in the bottom of the tank. Best to pump it out. The 110 or 115 probably refers to the compression reading that someone did. That compression is just slightly low, but is in the "normal" range-you should be just fine with those readings.

 

[John Drew]

Re: 1977-85hp Evinrude Carburetor adjustment screws

I took out the "brass screws" and two appeared to have smaller holes. When I blew them out, it was trash.
Now the engine runs excellent on low idle speed but still misses on high speed. You were correct on water in the tank. I found some in the carburetor. Is there an addetive which will take out the water or an inline filter in the hose to remove the moisture?

 

[emdsapmgr]

Re: 1977-85hp Evinrude Carburetor adjustment screws

If you've got water in the fuel, don't even try to filter it..just pump it out and go with new. Keep in mind that fuel is also stale and could have phase separated in the tank. Take the hose barb off the engine end of the fuel hose, hang it over the transom so the end is lower than the tank bottom. Put the hose over an empty container and prime the bulb a few times: it will drain the whole tank for you. An inline fuel/water separator makes a good addition to any engine. I wouldn't make much of how the engine runs till you know it is running on fresh fuel. It will run/idle with some water in the gas, but won't make any hp when under load.