997 Evinrude Ocean Pro 200HP

[dingbat]

This is driving me crazy.

The boat will not idle reliably below 1100 rpm. It looses rpm over a course of 20 - 30 seconds or so. Bump the throttle and it would recover, then 20-30 seconds later the cycle starts over again. If you let it get below 800-900 rpm, it could continue to drop, you get no response to throttle bump, then stall.

I did a link and sync. The butterflies on the port side where sticking, not allowing the throttle to close all the way. I thought I had found the culprit, but no....that increased the cycle time to 5-10 minutes.

I then pulled and cleaned the carbs. Found nothing to speak of. Reinstalled the carbs and found an increase in RPM increased when I blocked the intake on #2 carb. Tore #2 carb down and found nothing but the RPM no longer rises when I put my hand over it. I sprayed carb cleaner around the carb gaskets, base of carb, etc. without a response.

Symptoms:
1. Sneezes/coughs thru the carbs on random cylinders now and then.
2. It will "miss", for lack of a better description, just about stall, then come abruptly back to life on a regular basis.
3. Drop 200-300 rpm (no discernible miss) for a couple of seconds, then bounce right back up to 1300 - 1400 rpm again (on hose). This usually happens after I "goose" the motor by manually operating the throttle arm

Outside of the idle issue, it starts with the turn of the key and runs very well.

Any ideas?

 

[daselbee]

You have 8000 posts. I know your nick. I see your posts all the time....
Have you never read any of my posts on cleaning the throttle bodies?

This problem screams of a dirty throttle body. Search and read up. Maybe use the search term "calibration pockets".

 

[dingbat]

You have 8000 posts. I know your nick. I see your posts all the time....
Have you never read any of my posts on cleaning the throttle bodies?

This problem screams of a dirty throttle body. Search and read up. Maybe use the search term "calibration pockets".

To tell you the truth, I took the covers off while still on the motor and did a visual. Looked clean, put it back together. Lesson learned.......

The good news is that you where right on the money :thumb:. Some fine adjustments in the water and I should be good to go....Thx

 

[daselbee]

To tell you the truth, I took the covers off while still on the motor and did a visual. Looked clean, put it back together. Lesson learned.......

The good news is that you where right on the money :thumb:. Some fine adjustments in the water and I should be good to go....Thx

Are you saying by the phrase "right on the money" that the cal pockets in fact had clogged holes?

I think a great way to prevent that is to spray carb cleaner using the little straw directly into the brass idle bleed jet located in the front of the carb face.
That passage leads directly to the cal pockets, and will keep those holes open if you do it as a PM procedure.
If you use the boat every day, they will stay clean by themselves. If you use the boat once every six months, now you are talking varnish and gum build up.

All OMCs with plastic carbs are potentially affected by cal pocket clogs in the throttle bodies, and most everyone never bothers to really clean the TB.

 

[dingbat]

Are you saying by the phrase "right on the money" that the cal pockets in fact had clogged holes?

I can't honestly say.....a visual turned up nothing that looked clogged or restricted in anyway. I took the TB off and took in on the bench for sterilization.

No smoking gun but found a curiosity. The tapered part of the mixture screws for cylinders 3 and 4 looked "eroded" for lack of a better word. Grayish, streaked with some surface roughness. Not bright and shiney like the others. I would have replaced them if they were not $40+ each

 

[daselbee]

Probably not it. If you examine the cal pockets carefully, you will see 5 very small holes. The smallest is 0.010 in diameter.
Make sure you can see light thru those holes; you may have to operate the butterfly plates to see light properly.
They are so small, and they supply all idle and mid fuel to engine.

Mix screws should be at maybe 5 1/2 to 6 turns out if all is right.

 

[dingbat]

Mix screws should be at maybe 5 1/2 to 6 turns out if all is right.

The idle screws where out 6.5 turns when I removed them for cleaning. Might explain why its seems to smoke more than normal