Removal/Cleaning of low speed orifice/jets

[RFox10]

Hi -

I have a 1976 Evinrude 70hp (model 70673D). This motor sat for several yrs before I bought it. I've done a lot of work to it and finally got it running really well...except, when throttling from the neutral position to WOT, the engine bogs and will only run very slow, but all I have to do to get it to go is just bump the choke. It will take right off and run great every time. I've cleaned and rebuilt the carbs, replaced the power pack, replace the coil on then lower cylinder, new plugs, replaced the rectifier, replaced fuel pump, replaced fuel lines, new fuel tanks...among other things. My thought now is that the low speed orifice or "jets" on one or all of the carbs may need more cleaning. When I rebuilt the carbs I did not remove these because they were very tight and I was worried about stripping the threads. It looks like I can access and remove all three of these without removing the carbs, can somebody give me some tips on how to remove these orifices and how I should go about cleaning. I don't have the special jet screwdriver, how can I modify a regular screwdriver to make it work? Any ideas would be greatly appreciated. Thanks.

 

[Bosunsmate]

Re: Removal/Cleaning of low speed orifice/jets

I use a file or a grinder and grind a small screwdriver down to fit

 

[classiccat]

Re: Removal/Cleaning of low speed orifice/jets

The LS jet meters fuel when your throttle plate is closed. You have HS jets to worry about as well. (I have the '75 70Hp who's 3 carbs are sitting on my bench ready for complete tear-down)

If you're uncomfortable with fabricating your own tool, an orifice tool is still available for about $21; search PN: 0317002

 

[eavega]

Re: Removal/Cleaning of low speed orifice/jets

Two bits of information for you:

1. The specifications for making your own tool is here:

http://forums.iboats.com/engine-fre...ns-faq/carb-cleaning-instructions-244013.html

The tool is super easy to make, should take you all of 5 minutes to make it, all it is is a ground down screwdriver with a thicker blade.

2. You, my friend, are experiencing the ever-popular "Mid throttle lean" condition which was exclusive to the 1976 70 and 75 HP Johnson/Evinrude motors. You need to look up Evinrude TSB 1144 (There is a Johnson equivalent, but I don't know that number) that deals with this condition. To quote directly from the TSB:

"Some of the '76 Evinrude 3 cylinder motors have developed a flat spot or hesitation, and in some severe cases, a tendency to die during mid-range acceleration such as when pulling up skiers. If blipping the choke momentarily helps the motor accelerate through the mid-range R.P.M,. a lean carburetion condition is indicated..."

The TSB goes on to describe modifications to the carburetors including drilling out a couple of ports in the high-speed nozzle, drilling out the calibration ports (under the core plug) and replacing the idle orifice with a larger size.

There is two ways to see if your motor has had the modifications made (since this TSB came out in September of 1976, there is a chance that the modification has already been made on your carbs). Either there will be a stamped "X" on the carb body ( to indicate the modifcation made), or you will have .032 idle orifices instead of .030.

If your carbs are unmodified, I would suggest giving this mod a try, as it resolved the problem for me, and for a few others that have been made aware of this TSB.

Good Luck.

Rgds

 

[RFox10]

Re: Removal/Cleaning of low speed orifice/jets

Thanks Guys.

Ghostrider - how do I know if I have the .030 or the .032 jets installed? Are they stamped or anything?

 

[eavega]

Re: Removal/Cleaning of low speed orifice/jets

Thanks Guys.

Ghostrider - how do I know if I have the .030 or the .032 jets installed? Are they stamped or anything?

Yes, they should be stamped on the side of the head.



it will read 30 (as this one is one of the old jets) or 32.

Rgds

 

[RFox10]

Re: Removal/Cleaning of low speed orifice/jets

Awesome. Thanks Ghost rider. Where can I order the .032 jets? Do happen to know the part#? I PM'd you a few questions on this topic.

Thanks.