1995 Johnson 175 Fast Strike - Idle adjust screws?

[trxxx250r]

I've had this boat out 2 times since I got it running about 6 gallons thru it each time and it runs great, however, the plugs are a light tan evenly. The 2 bottom cylinders are the lowest compression (100 &105) and they are a little darker. The other cylinders are about 115 PSI. I ran the boat at full throttle a bit and about even split between half throttle and idleing around.

I'm a little concerned the motor is running lean as per the plug readings. I've been reading and from what I gather the idle screws should be approx. 3 turns out on some motors and 5 on others. I checked the top 2 and they are 10 & 1/2 out! Are these "idle air" screws or "fuel screws"? In other words, the further out the screws are the richer... Or the reverse? It seems to me the further out the richer.

Is there something odd about that?

Is it possible I may need to go up on the idle jets since the idle screws are so far out?

The motor spits or coughs a little at idle when the motor in in forward and at about 800-900 rpm.

Any help is appreciated! It seems like a lean condition even though the moter runs good, I don't want to burn it up!

Please help.

 

[trxxx250r]

Re: 1995 Johnson 175 Fast Strike - Idle adjust screws?

Anyone?

Thanks.

 

[SUBMARINER47]

Re: 1995 Johnson 175 Fast Strike - Idle adjust screws?

my manual says the screw at 8 o'clock is the idle screw and out is richer

 

[trxxx250r]

Re: 1995 Johnson 175 Fast Strike - Idle adjust screws?

Well, I finally got the chance to work specifically on the idle screws. First, the screws were set all over the map from whoever worked on it last. From 2-1/2 out to 10-1/2 out, some were 6 etc... No wonder it was coughing at idle, especially that one cylinder at 2-1/2 out.

So, since my plugs were mostly burning lean I decided to just turn them all 9 turns out an see what happened. The coughing went away and the boat idled great. Came out of the whole strong. Ran the boat all afternoon. However I still didn't know whether I was rich or lean and on which cylinders, so I pulled the plugs and that told the tale. Some cylinders were just right, 2 were a little rich and one a little lean. So, I adjusted the 2 bottom cylinders to 8 turns out and the port side top cylinder to 10 turns out and left the rest at 9.

I'm not sure if this is the best way to tune the idle mix screws but it makes sense to me and now the motor runs great and I'm not running too lean, at least not as much as it was. I'm sure I will do a little more fine tuning but I believe I'm pretty close at this point.