F60 losing power

[tidnish1]

Hi Folks,
I have a 2003 F60TLR with 85 hours on it. Its new to me and seems to be losing power. Deal is, when I start out, it seems to rev up fine, up to about 5200 RPM with a 10.25/14 prop. Almost as soon as Scout 155 gets on plane like 30 seconds), the engine drops back on power, down to 4000, then drops back to about 3200. It seems to drop quickly, like its losing a cylinder. When I pull the throttle back, it shakes like its missing. If I idle for a few minutes, it will then pick up speed when I advance the throttle, only to drop down to 3000 or so in about 10 seconds. While doing this a few times, I squeezed the fuel bulb and it didn't make any difference so I suspect its ignition.

Any thoughts on where to look? Plug or coil? Anything?

Thanks very much for any suggestions.

[99yam40]

guessing is not the way to go.
Test things to see if you are loosing spark and on which cylinder if it is.
timing light hooked to different plug wires should show if spark is dropping

[tidnish1]

Thanks 99. I absolutely agree guessing isn't the way to go. I've checked the fuel system, including the lines from the tank, the large filter outside the motor, the fuel line including the bulb and fitting, and the filter inside the motor cowl. This all looks fine. Seals where its supposed to seal, flows freely where its supposed to flow.

I pulled the spark plugs, they looked fine. Connected one of them to a plug wire, grounded the outer housing, and cranked the motor. No spark, nada. Tried another plug on the same plug wire, same results. Tried another plug on the other wire from the top coil, no spark. Tried another plug on one of the wires from the bottom coil, and say a glimmer of a spark. It was really week (in my opinion) but evident. Tried another (starting to repeat plugs now) on the other wire of the bottom coil, same week spark.

So, I'm now focused on ignition, not fuel. It looks to me like coils, or the rotor that energizes them. Is there a test I can do to narrow this down? 99 mentioned a timing lite on each plug but I don't think this will prove if its week coils (if they even go week) or something further up the ignition system,

Thanks again for any help.

[tidnish1]

Some test results and observations

Did some testing tonite. First, I put a spark gap measurement tool on the plug wires, set at 0.35" All coil plug wires did show a spark across this gap but to me, it looked weak and 'thready'. Certainly wasn't bright or blue. Tried the plugs again and they all showed a spark, but again it looked weak. The battery is new and spins the motor quickly without any problem (For comparison, I tried the spark gap tester on my 15 year old lawn mower and the spark across the same 0.35" gap looed stronger to me, and I'm pulling this over by hand).

Next, I measured the coils: Orange to Black wire measured .5 to .4 ohms on each. Spec is .08 to .11 so these seem to have a high resistance. Plug wire to plug wire measured 4.2 Kohms and 4.4 Kohms. Spec is 3.5 to 4.7 Kohms so this seems OK.

Next I measured the Charge Coil resistance, 333 ohms against a spec of 272 to 408, so seems OK. Pulser coil resistance measured 512 ohms against a spec of 396 to 594 so again, seems OK. Checked the Pulser Coil air gap and its fine at 0.03".

Sorry for the long post but can anyone comment on the possible problem? From the measurements, it seems the coils may be a problem but I'm concerned about how consistent the measurements are between the two. If they're bad, both have failed the same and I just don't know how likely this is. But, if the resistance is high across the primary coil, does this translate into a weak output on the spark plug leads? Or is it as simple as bad plugs (new last fall and only run for 1/2 hour, the look new).

Thanks Folks,

[99yam40]

get a DVA adapter and read the voltages into and out of the CDI to make sure they are in spec, unless you happen to have the proper voltmeter to read the peak voltages in these systems.

It is a lot better than looking at ohms

[tidnish1]

I'm trying to get my hands on one but not much luck yet. From the measurements I've given, is there anything that stands out as a potential problem?
Thanks

[tidnish1]

More info

Hello. I had a chance to test the overheat sensor, works fine. Also looked at the fuel system a bit, the fuel pump pumps, the filter is clean. I looked at the top of top carb (there is a plate there that can be removed), and its as clean as it can possibly be. I stopped short of removing the carb assembly. I'm still looking for a DVA adaptor (or making one as it appears to be a simple circuit)

So, as far as I know now, the coils have a slightly high resistance on the primary side and the spark appears weak. The fuel system looks clean and appears to be fine. I still have to test the coil output, the stator output, and the CDI output once I sort out a DVA adaptor.

Can anyone comment on the results so far?

Thanks

[tidnish1]

I like to complete things. Someone suggested the problem might be a stickey needle on one of the carbs, leading ot insufficent fuel flow at high speed. Its exactly what the problem turned out to be. Bottom carb was 'green' with corrosion and the needle did not move freely. Fuel would fill the bowl under light loads but when I accelerated, it would burn up and not be refilled due to needle stickage. A clean needle valve is a happy needle valve.

[Wellcraft238]

Ive had this occur on 2 different occasions. Once on an Evinrude 4 cyl 2 stroke 140 hp motor. After chasing the intermittent issue for quite a while, I discovered that the coil pack had a crack in potting in the back of it and would heat up, and then arc against the block causing 1 cyl to drop off, and tehn return after a bit and tehn drop off again.

My recent issue with my 95 250 2 stroke - it wouldn't atart...and finally did later on that day in the driveway. I ran it a week later and lost a cyl and quickly lost the rest of them.. it was the stator. Put a used on in and I'm back in action..

[madharchod]

have you had a diagnostic done ,since your engine gives intermittent failure the chances are your throttle position sensor is gone so replace it and see what happens as i dont think there will be any other problems

[rodbolt17]

get the DVA adapter.
test pulser coil outpts and charge coil outputs.
test CDI output.
then go fix the fuel system.