Adjustment Steps After Carb Refurb/Re-installation?

[crybdr]

I have a 1992 40HP Evinrude Outboard (VRO disabled). It sat a lot this summer due to a back injury that had me out of commission. The 3X we did take it out this year, it ran a little worse each time. Stalling at idle has been getting progressively worse this year. Last week, I couldn't even get it to stay idling. I changed over the gas in the tank and bulb to a fresh premix, and now it idles, but dies immediately when you try to engage the drive (I got it to go into gear once while moored to the dock, but had to go real quick with the throttle lever). I have 2 different tanks and bulbs on the back - both produce the same results.

It had compression tested a year ago and that was fine. The shop I go to has done work to try to fix the poor performance from previous years (thermostat replacement, throttle linkage adjustments...) It sits A LOT unused in the sun - and I don't know the condition of the carbs as I have only owned this engine for 3 years. So, I removed the carburetors and am having them professionally rebuilt at a local carb shop.

I'm confident that I can put 'humpty-dumpty' back together again (took lots of pictures and time during disassembly). It's a really tight space to work in, but it's logical how it all goes together.

However, what adjustments will I need to make in order to get the right mix of air and gas into the engine? I have zero experience in that area.

Any thoughts or links to vids would be very appreciated.

 

[sutor623]

Well, I would hope that the shop rebuilding your carbs would be able to get your motor honed in. Most on here will tell ya to get a service manual. It will help you learn that motor inside and out. For now, check out the link in my sig. It is a link to free outboard motor manuals online. Have a looksee for your particular motor and come back with any ?'s once you start to get your hands dirty.

 

[crybdr]

Thank you for the links. The boat is dead in the water on our dock. So.....the 'shop' won't have an opportunity to hone them in. The shop is dedicated to rebuilding all sorts of carburetors. When I brought in the bare carbs the guy behind the desk took one look and said "40HP Evinrude?". Yep.

I'm doing the work in hip-waders and the water is starting to get cold.

 

[sutor623]

I'm doing the work in hip-waders and the water is starting to get cold.

Yikes!! Well I'm sure we both have been caught in worse situations!!! Good luck. The link and sync for these two carb motors is pretty cut 'n dry. Will all be outlined in the online manual.

 

[crybdr]

Well.....

After a meticulous dis-assembly, a week at the carb-shop for a pro-rebuild, and a meticulous re-assembly of the new carbs, the situation is no-better and no-worse.....

Now, I'm thinking the disabled VRO system fuel pump (mechanic disabled it 1 year ago to get us on pre-mix due to it throwing in WAY too much oil - it ran great for a year after that) or a fuel filter might be the culprit (fuel filter replaced 2 years ago). *does the fuel filter need to be replaced every year..... probably?

After the fresh carb install, the engine started up, ran at high idle for a little bit, began to ramp down like it should - then died. Subsequent restarts could happen, but I had to bump the primer on the key occasionally to keep it going.......it then runs for a little while, then slows down and dies. The primer bulb won't get 'rock-hard', but it's obviously moving fuel, and gets firm - fresh pre-mix in the tank too.

I have read about others converting from VRO to pre-mix for this motor. Seems like most of them have had success with adding the dedicated pre-mix fuel pump - there are pre-drilled and tapped holes on the block for this new fuel pump.

I have a retired 'boat-whisperer' who works out of his driveway about a mile away that is willing to make a house call for me. So, I'll have a pro looking at it. But in the meantime, if anyone has an opinion, I'm all ears.

I'd rather confidently drive this thing into the landing to be yanked out - rather than try to find a tow......But we'll see how it goes...... :-(

 

[Tim Frank]

Sounds like you are guessing and prepared to throw some parts at it until something "sticks".

That can be an expensive sport.

As suggested earlier, I'd also be one of the ones that would suggest getting an OEM manual.
You need to be systematic in your approach to troubleshooting; that way you actually zero in on the root cause, and then can effect the correct cure.

1) do a drop test to make sure both cylinders are firing.
2) If not, do a compression check (good idea to do one anyway). You said you had one done last year and it "was fine"; but the motor also "was fine" last year wasn't it? Things change.
3) Actually check spark with a gap tester set at 7/16" to make sure spark can make the leap.

If all above checks OK, should take LT 1/2 hour, back to the fuel system.

 

[crybdr]

Just finished a 45 minute session standing in the water with my boat mechanic.

-Compression is good - both cylinders just above 125, well matched.
-Spark is good on both cylinders.
-Fuel flowing freely to both carbs

He was as perplexed as I am.

He removed the air box in front of the carbs and manually choked the air flow with his hand to each of the carbs to test them. His best guess is that the top carb may still have something wrong in the idle circuit (physical crack or poor rebuild). We pulled the top carb and he's looking at it tonight.

????

 

[Tim Frank]

How did you test the spark,
and ....did you do the drop test?

 

[crybdr]

Spark was tested with a gizmo that he brought along (a cord with connections for spark plug and plug wire with a small metal chamber in between with a window to look for spark). Both cylinders show spark.

I don't know if we did the 'drop test' or not. I'll need to look that up.

This guy is a retired marine mechanic, old-school. I'm confident I'm in good hands. But, he's scratching his head too it seems.

 

[crybdr]

Made some diagnostic progress today.

My mechanic brought back the top carb after he took a look at it and cleaned it again. We re-installed and tested, engine won't idle.

He also brought a similar carb from his stockpile. We installed that one and the engine runs and idles.

So, something in that my top carb is still messed up on the idle circuit, no amount of cleaning/rebuilding has solved it.

I've ordered a new carburetor assembly.

 

[crybdr]

No Title

As was recommended by many - I have the manual for my engine now. The service manual is exceptionally well written and 'deep'.

I may have found an obscure fix for my dead (rebuilt 2x professionally) carb. Step 16 of the carb rebuild sequence says to check the emulsion tube pickup/carburetor fit for any leaks - not something that can be disassembled. Test from manual - flooding with isopropyl alcohol with the carb inverted may have shown a small leak - it's hard to be sure. So, the fix from the manual is to apply a drop of drop of OMC Ultra Lock to that joint. I used Locktite 271. Capillary action swings the drop around the entire joint - just make sure to keep the carb tipped so that the Loctite doesn't run into the idle ports. Pic attached of the potential fix. It needs 24 hours to cure - will install and test tomorrow.

I also took a look at my 'Link and Sync' relative to the manual. It's off from the manual. Pic attached. I haven't touched this stuff since I received the engine 3 years ago. Should I start at square one and work forward as the manual says? Why could these items be so different from the manuals recommended settings?

Thanks for any insights you might provide. I'm a little better informed now......

 

[crybdr]

Per an earlier question. The drop test was performed while my mechanic was here helping.