Why does it do this??

[CPTom21]

When I pull my throttle back, so that I can shift, my engine sputters out. It seems that if I go below %10 throttle my engine shuts down. Then it usually takes a few minutes before it will start up. It's a 40hp 1964 Evinrude ob on my 14' Starcraft.

Question 1: What am I doing wrong?

Question 2: Could I do serious damage if I'm shifting at %10-%25 throttle??

 

[boobie]

Re: Why does it do this??

Check your compression and spark. If thats ok you may need some carb work and a good sync & link. As to the shifting you can do damage.

 

[nwcove]

Re: Why does it do this??

have you rebuilt the carb(s) in the last few years? and yes, banging it into gear at higher than normal rpms wont do it much good.

 

[oldcatamount]

Re: Why does it do this??

It's time for a tune up. New plugs, points, condensers, and a carb kit. Be sure that you are running fresh fuel/oil mix. Check things over, like fuel line connections, plug wires etc. The motor's got some age to it and things need to be replaced or repaired. Do a compression test to see if the two cylinders are close to each other. Shifting gears at quarter throttle can be bad for the gears. A tune up will allow the motor to run slower and shift better.

 

[CPTom21]

Re: Why does it do this??

Thanks for the responses folks. Actually the engine was rebuilt in this Summer. I bought it in May, got it home and it didn't even have a spark. I took it back to the dealer, and he fixed it(no charge of course). It worked great the first few times I used it. There is a rotating switch next to the choke that is labeled "lean". Does this possibly have something to do with it, and if so what??

 

[robert graham]

Re: Why does it do this??

Sounds like a fuel mixture control...would probably help it idle to turn it(in 1/4 turn increments) towards the "rich" side until it improves. A slightly richer mixture may also make it start more easily. Do you have a fuel filter on the motor to maybe keep trash out of carb/jets?...if not, maybe add one in your fuel line. Good Luck!

 

[kfa4303]

Re: Why does it do this??

Hi CPTom21. Sounds like you need a carb clean/rebuild to me too. Not to wory. It's a quck, cheap, easy job you can do yourself. Here are some handy links that can walk you through the process and give you some great all around info on your motor. Use the term "Big Twin" and you'll find even more information on your motor and those of similar vintage. To answer your question, yes, the Lean/rich knob may need to be adjusted slightly, but be sure you read the link below, so you do it properly. It's used to fine tune the fuel/air mixture in the engine. Rotating it clockwise in small increments, "leans" (i.e. less fuel to air) out the mix and causes the rpms to increase. Conversely, backing it out slightly by rotating it counterclockwise makes the fuel/air mix more "rich", or "fat", and should make the rpms drop slightly. Again, give the links a read before youstart tinkering. Keep us posted. Holler if you get stuck.


http://www.iboats.com/Carburetor-Ki...15.1964--**********.598707941--view_id.174131

http://forums.iboats.com/showthread.php?t=167352
http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm
http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm (smaller motor, but same procedure as yours)
http://www.outboard-boat-motor-repa...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm (smaller motor, but same procedure as yours)

 

[CPTom21]

Re: Why does it do this??

Awesome thanks everyone!! It's still in the 70's here in Syracuse, and I'd like to get a few more uses out of her. With this info i should be able to do just that.

 

[CPTom21]

Re: Why does it do this??

Thanks again everyone. I played with it for like 2 hours yesterday, and it runs beautifully!! All we had to do was adjust the mixture knob. One more question though. My Dad has carb spray that works wonders on all our lawn mowers, and snowblowers. Is it ok to use it in my 1964 Evinrude?? The details on the container say that it's good for cars, mowers, BOATS, etc..., but I just want to make sure that it won't do something screwy to the engine. (He may use it without me knowing because he has a tendency to do that.) Thanks!!

 

[kfa4303]

Re: Why does it do this??

Hi CPTom21. Glad you got her running better. Most folks here are NOT big fans of the aerosol style carb cleaner that you spray into the carob throat as the motor is running. It's fine to use it if you take the carb off in order to rebuild it, in which case the aerosol carb cleaner is great for blowing out the passages. However, you don't really want to use it on a running motor. Carb cleaner is an organic solvent designed to dissolve organic solids like carb good, dirt and the oil in your fuel!!!, which is vital for keeping all of the innards of the motor properly lubricated. The carb cleaner would actually dissolve this oil and cause it to be burned off without doing its job. As a result, your motor's internal components will be starved for oil, which is about the worst thing you can do for these old 2-strokes. I would recommend removing the carb and thoroughly cleaning it and replacing all of the consumable gaskets (i.e. "rebuild" ) the carb. It's a quick, cheap, easy and routine job to do. You can get a carb kit right here at iboars for about $20, or you can get one at NAPA auto parts store. If it's not in stock thye can have there by the next day for FREE. Again, the aerosol carb cleaner is fine for cleaning/blowing out the passages when you rebuild the carb, but not advised for use on a running motor. You may also want to decarb your motor. No, that doesn't mean removing your carb (LOL), it means you want to "decarbonize" the pistons. Over time black, carbon deposits can/do build up on the pistons and rings and can impede performance. By removing theses deposits the internals are allowed to move much more freely and smoothly. Sea Foam and/or Deep Creep is a great product available at any auto parts store for abut $10 a can. It comes in liquid or aerosol form, either of which is fine. It's great stuff and will work wonders for you motor, especially if it's been sitting a while. It is safe to spray Sea Foam into the carb as the motor is running. It will smoke like #@$#@$, but that's what you want. Those are all of the carbon deposits burning away. Spray 4-5, 4-5 second sprays into the carb as the motor is running at med-high idle. When you spray in the Sea Foam the motor will smoke and the rpms will drop. You may have to turn up the idle a bit to compensate, but that's normal. The rpms will come back up again when you stop spraying. After doing this 4-5 times, let the motor sit for 20-30 min, then start it up. Again, it will smoke like #$#@%#$%, but that's normal. Run the motor at med-high idle until the majority of the smoke burns away, then get the boat on the water ASAP and open up the motor up to WOT to bring the motor up to temp so it can burn off the remaining deposits. You'll be amazed at the difference it will make. Now that you know how all the knobs do and how to adjust them, I would suggest you do a carb rebuild and/or decarbonization (Sea Foam) treatment. The whole job will cost about $30 and take an afternoon. These links can get you started.


http://www.iboats.com/Carburetor-Ki...15.1964--**********.704433472--view_id.174131

http://www.duckworksmagazine.com/04/s/columns/max/25/index.cfm

http://forums.iboats.com/showthread.php?t=167352

http://www.youtube.com/watch?v=sLOuUWV4GrQ

http://www.youtube.com/watch?v=vPVqBrhRXUU

 

[CPTom21]

Re: Why does it do this??

Thanks again kfa4303!!