1973 Evinrude 20 HP idle Problems

Hi Guys I have a 1973 Evinrude 20 hp fast twin that is having problems! I am literary rebuilding the carb as I am typing this well its soaking in carb cleaner. It had what lots of people online where saying its a lean cough so I adjusted the low speed idle needle is seemed to sort it out but when I rev it up (not in gear) and back down again it stalls it at temp when it happens this is my 1st boat and not sure really where to go, next the carb inside was clean so I don't think its that. when I have put it back together I will post video, I have put new spark plugs in. but when im in gear and its on the boat its fine at high speeds just doesn't like low speed its fine on the lake its just when I try to get it in the dock it hard lol :facepalm:.

Any advice would be appreciated its a old motor but im sure it will be great if I can get it back to its former glory. I don't mind spending money on it coz like the sound of and on my 14ft boat it will push it at 30 mph on the GPS.

Thanks

Nick

Re: 1973 Evinrude 20 HP idle Problems

Hi Nick. Welcome to iboats. Here's are some great links that will help you familiarize yourself with your motor. You really only need three things to make these old 2-strokes run; compression, spark and fuel. You'll want to use 50:1 fuel oil mix, Champion J4C or J6C spark plugs, and you'll always need to run it in a test tank as you cannot use "muffs" on motors of this vintage.

Maintaining Johnson E & FD Serie
1973 Evinrude 18305A 18 hp Outboard Motor Parts

Re: 1973 Evinrude 20 HP idle Problems


This is how its running now :encouragement:

Re: 1973 Evinrude 20 HP idle Problems


This is how its running now,

The motor would not rev up and then sit back at idle but seems ok now, I took carb off rebuilt it using car repair kit from eBay, slow speed idle needle was 2 1/4 turns out. I'm not sure if that's right as the kit said only 1 turn out but had a lean cough like that and would not run. seems ok to me but any advice would be greatly appreciated!!


Thanks

Nick

Re: 1973 Evinrude 20 HP idle Problems

Hello again Nick. She looks and sounds pretty good to me. You may be able to get it to idle down a tiny bit more by backing out the idle set screw found where the tiller meets the vertical throttle tower which passes through the lower cowl. By backing the screw out, you retard the timing slightly, which will reduce the rate of spark and lower the idle. If it gets too low, you can then turn the lo speed needle in on the carb to raise the rpms. The idea is to strike a nice balance be tween the two. While 2 1/4 turns is a bit more than most, if it works, it works. Just make sure that the needle itself is snug and won't back out due to vibrations while underway on the open water. You should also find that the idle will drop once you put the motor in gear and have it under load. You may also want to add another inch, or so of water to the test tank which will offer a bit more back pressure for the exhaust. All and all I'd say it's in good shape. If you can get it to start and stop 3 times in a row at home, I say hit the water and give it shakedown run. Good luck. Keep us posted.

P.S.
I'm curious to know which automotive carb rebuild kit you used. It may come in handy for more folks on the other side of The Pond. Cheers!

http://forums.iboats.com/engine-fre...sorted-carb-variations-joe-reeves-167352.html

Re: 1973 Evinrude 20 HP idle Problems

kfa4303 said:

Hello again Nick. She looks and sounds pretty good to me. You may be able to get it to idle down a tiny bit more by backing out the idle set screw found where the tiller meets the vertical throttle tower which passes through the lower cowl. By backing the screw out, you retard the timing slightly, which will reduce the rate of spark and lower the idle. If it gets too low, you can then turn the lo speed needle in on the carb to raise the rpms. The idea is to strike a nice balance be tween the two. While 2 1/4 turns is a bit more than most, if it works, it works. Just make sure that the needle itself is snug and won't back out due to vibrations while underway on the open water. You should also find that the idle will drop once you put the motor in gear and have it under load. You may also want to add another inch, or so of water to the test tank which will offer a bit more back pressure for the exhaust. All and all I'd say it's in good shape. If you can get it to start and stop 3 times in a row at home, I say hit the water and give it shakedown run. Good luck. Keep us posted.

P.S.
I'm curious to know which automotive carb rebuild kit you used. It may come in handy for more folks on the other side of The Pond. Cheers!

http://forums.iboats.com/engine-fre...sorted-carb-variations-joe-reeves-167352.html

Click to expand...

Hi the carb kit I used was Johnson Evinrude Outboard Carb Rebuilding Kit 18-75HP got it off ebay but paid ?34 about $55 you guys over the pond can get them I saw for about $30 was good kit had all the gaskets and bits and bobs you need in them.

what you where saying there about the low speed idle I thought it was a little high too but when I was putting the linkage back together the throttle plate leaver thing was all the was back, but you said it changes the timing, so that should drop the RMP right? I will post a video tomorrow if I get time its father's day over here and my 14 week old is taking me out for a meal so not sure but will deffo try at some point this week.

My next question was going to be what is the best prop for it as it still has the original one on, I have seen them with newer looking props the boat its on is light GRP boat, it will get up on plane fast 5-10 sec's and hits top speed not long after that but I want to pull a rubber ring and other water toys the faster the better I have seen 20 HP Evinrude Outboard Boat Propellers 1969 - 1973 - iboats the one in the 11" pitch might work but would like to know how much more I can go if any. Then im redoing the boat its self but that should be easy ish I think as its just a fresh coat of gelcoat all over and seats / side lining. Im a electronic engineer so will be putting Amp sub speakers lights plug sockets in and a larger fuel tank with sender unit nice white gauges with blue back light Fuel, Speed, Battery. I have seen uni fit tachometer I might try to put on but not sure how good they are. I enjoy doing it at the min and have a image of what it will look like in my head its just if I can get it to look like that lol. do you have any advice on the best way to tackle it?

Thanks Again for your help

Nick

Re: 1973 Evinrude 20 HP idle Problems

Hello again Nick. Congratulations on the 14 week old! You must be busy indeed. The stock idle set screw I was referring to is usually made of nylon and located at the junction of the horizontal tiller throttle assembly and the vertical throttle tower (see pic below). It acts as a stop to prevent the twist throttle from going too low and stalling the motor. It is also used to help dial in the idle. Turning it clockwise, should advance the nylon screw and advance the timing slightly, while backing it out should lower the timing. You can then use the low speed needle on the carb to further dial in the idle. I try to back out the nylon set screw until just before the motor stalls. I then twist the low speed needle in 1/8-1/4 turn and wait 10-15 seconds for it to take effect. This will raise the rpms slightly to prevent the motor from stalling after which point, I again back out the idle set screw to retard the timing thus lowering the rpms again. You can then repeat this procedure until you get as low an idle as possible. Don't be surprised if the nylon screw itself is quite deteriorated. Mine was so bad, that I simply replaced it with a 1/4 x 20 x 3'' stainless steel machine screw. It's also best to do the final adjustments on the open water with the boat in FWD gear under a typical load, but you should be able to dial in a pretty good idle in the test tank as well. As for the tachometer, there are several aftermarket devices. Probably the best know is a little device called a "Tiny Tach". It's an ingenious little device that lets you retrofit a tach onto any 2 or 4 stroke/cycle motor without making any modifications whatsoever. You simply wrap a lead around one spark plug wire and the rpms are then displayed on a small LCD screen. It also acts as an hour meter. There are other brands that may cost less, but I've heard they're generally not as well made. Here are some links and pics that may be of use. Herewith, hope they serve.




Johnson Outboard Marine Motor Tachometer / Hour Meter Install - YouTube (Tiny Tach in action)

Evinrude johnson 20 OMC outboard per?moottori - YouTube (nice low idle on this 20hp)
20 hp Mid 80's Evinrude Motor - YouTube (another nice little 20hp)
Johnson 20HP Outboard - YouTube (one more)