intermittent rough running 60hp '97 Evinrude

[mckennatim]

Running at 'no wake speed' engine sounded good for 9 seconds then rough and throaty for 12 seconds for the entire 10 minute ride to the boat ramp. Varying speed slightly didn't change the pattern. First time in for the season was the day before and it ran fine on a little trip to the beach. On the return trip it wouldn't accelerate so I eased back and limped home at low speed hoping that I wasn't starving a cylinder and scorching it. Now it is back in my driveway.

The engine is a '97 60hp (E60TLUEA) 3 cylinder carbed with vro2.

The bulb wasn't real hard; pumping it up didn't change things. The gas tanks were clean and dry with new fuel. None of the system check lights came on though they cycle on for the self test. I can't be totally sure that the oil level went down since I only ran 2-3 gallon of gas. I had oil in the first 6gal tank but switched to the pure gas tank when it started acting up; no difference.

Got this engine last year, about 15 hours ago. Changed the fuel filter and rebuilt the carbs back then before I even used it.Ran a 'storage mixture' in for 15 minutes at the end of the season. So far...

-plugs look similar to each other
-compression is 140, 140,140

what should I try next..

-replace the fuel filter?
-clean the carbs?
-change the gas line from the tanks to the engine?
-??

[Solarman]

I would definitely go back to pre-mix to prevent damage, then investigate problem further.

Good luck.

[mckennatim]

So I;m running with oil in the tank and here is the status

So far... winterized by the book, used new fuel in clean tanks then... rebuilt carbs, changed fuel line, changed tank, new fuel filter, new plugs, checked spark, checked compression.

here is a video of WOT

Not sure where to go with this as my vacation slips away

[Solarman]

Ok. ”plugs look similar” , doesn't say anything to me. Similar doesn't tell me how they're burning. Couldn't view the video?
Pumping bulb is a good thing. It still could be a fuel related issue? But it's difficult to tell. Are all carbs adjusted identically, air mixture? Set by the book?
Post back a little more info, does motor run good at any speed?
Is it possible motor is in a limp mode?
If not running smoothly at idle after the 9 sec, did motor stop firing on all cylinders?

Post back when able.

[mckennatim]

Plugs look the same color, have the same gap, same wetness, when one is disconnected you notice.

Hopefully this link to the video works. If not I will change it from mp4 to another format.

I thought if there is no change at WOT while pumping bulb that eliminates fuel pump as the issue.

The carbs are adjusted identically, by the book, first by me then by a certified Evinrude tech at Diamond Marine in Ipswich.

Motor runs great at idle and low speed.

Not sure what limp mode means, will research.

Once you pull back the trottle to low speed, motor sounds smooth.

[Solarman]

Limp mode means, motor is trying to protect itself because something is not right. The motor limits RPMs for a number of reasons, different RPMs can tell a little about what's wrong sometimes. What RPMs is you're motor running smooth at? And what RPMs is motor maxing out at? Not going over?

Post back when able.

[mckennatim]

not sure, don't have a gauge

[mckennatim]

Turns out it was the fuel pump. When Jeff (of Diamond Marine) watched the video it pushed him back to thinking it was a fuel problem; the slow repetition of surging and dying out did not seem to be electrical to him. When he took it out, he too pumped up the bulb when it was dying and it had no effect; so the common wisdom that if pumping the bulb has no effect, you can rule out the fuel pump turns out not to be true for these VRO2 type pumps. My mistake was to only check the choke at low speed. I though I was verifying that it wasn't stuck on but Jeff choked it at full-speed-dying-out and it came back to life. That was enough for him to decide it was the fuel pump.

So I spent the afternoon fishing in beautiful Ipswich MA, $1,200 poorer and with 4 weeks of summer having slipped away. $368 of it was Jeff repeating what I'd already done, plugs, fuel filter, rebuild carbs, change out the tank and hose. You see this kind of 'professionalism' all over our culture, from medicine to mechanics. The next $832 was 3 hours of labor + the VRO2 pump marked up 25% over what you can get it for from marineengine.com. I don't think they got rich off this job, between 2 trips to put it in the water, they probably spent more than 6 person hours.

So I learned a couple of things about diagnosing. Turns out there was no magic bullet of high speed tank or fancy test equipment. The two likely scenarios that I didn't want to get wrong were power pack or VRO2 pump. I could have bought both of those high price items + a coil, carb kits tank, hose and filter for less than 1/2 of what I spent at the certified tech. I shouldn't have chickened out, I was afraid to be just an (expensive) part replacer. Oh well. Thanks for all your help. Happy boating.

[Solarman]

Thanks for the update.

This is not a blame game. Those of us here try to help, we are boat owners also. We are not all professional mechanics (some here may be?). But most are not.

A tach is very helpful with how motors are running, but some don't have them. It helps greatly where ears don't always hear the changes in RPMs, unless the changes are drastic enough to be noticeable.

Often many owners do the same as you, replace a number of items, but hold off on the expensive ones.

The ”surging” at higher RPMs is normally fuel related, and still can be a number of different causes.

Good luck, am glad you're up and running again, and thanks for the update.
Happy boating to you also.