05 Johnson 2 stroke 115 hp hesitation at wot

[boling]

This just started happening, I get up to full speed, after a while (2 or 3 min), then it acts like its fuel starved. Slow down, fine, try to speed up,starts hesitating again. Idle is good.leaving the dock after sitting is fine, always starts good. I replaced the fuel line and tested siphon, pulling about a half gallon out, good flow. Checked the screen at fuel pump, looked fine, washed a couple of particles out and put back. Took it back out, same problem. Any ideas?

Thanks for any advice.

 

[jakedaawg]

How old are the plugs?

When you say "tested siphon" do you mean you somehow tested the fuel pick up from the tank?

Have you pulled a fuel sample into a clear jar?

Plumb a tee into the fuel line before the VRO and attach vacuum gauge (scale of 1-10 in/Hg) with a length of clear hose. Report back in/Hg at various rpm's and whether or not you have air bubbles visible in the clear hose. Since your issue occurs under load at WOT you will need a helper and have to perform this test on the lake. This is an important test for your situation.

A spark test and a compression test will also be required.

 

[jakedaawg]

I forgot to mention that you should also do a test run on a known good portable tank with a known good 3/8ths in fuel line.

 

[boling]

Plugs have maybe 50 hours on them. When I attached the new line including the bulb, I hung the end of line down below tank level, and started the flow by squeezing the bulb several times. I let about a half a gallon out, the flow stayed constant. I saw no bubbles, and the rate was far more than I would expect the engine to ask for at wot. That being said, I did not check the vro line for leaks. Maybe tomorrow

I'm at the nc coast this week, and did not bring too many tools.

 

[boling]

No Title

Noticed this today while inspecting the throttle linkage, The crack goes the entire length of the roller, and the it was pushed up partially when I found it. Could this have been the culprit all along? Certainly if the timing advances without the throttle moving full open, i would think power loss. Am i on the right track?

 

[weaverunner]

If anything, you would be noticing idle issues if that cam roller was bad enough (i.e. chunks missing). It looks like it's on its last legs but not to cause the issues your experiencing. Definitely replace it before it causes you any issues.

So, it runs fine for the first 1-2 minutes after the first (cold) start and then it misses or hesitates as you give it throttle? Sure sounds like your power pack is on its way out.

 

[boling]

I'm going to replace the part and check it again on the lake. When I found this yesterday the outside of the roller had risen above where the cam would make contact.

. It was progressively getting worse each time I checked it. last time i was out, barely left the ramp before it started losing power. Still could be the pack, but I think the moving roller has to be partially to blame. BTW I have replace the plugs as well.

 

[ondarvr]

If the power lose is sudden, like someone flipped a switch, then it tends to be electrical, if it's slower and smoother, then start looking at fuel delivery.

From what you've said so far it sounds electrical, but not a timing issue, more like a coil failing as it warms up, could be a power pack too, but coils are the first thing to look at.

​Use a timing light to check for spark on each cylinder while it's acting up. Or remove one plug wire at a time and see how it performs without that cylinder firing, if you remove one and nothing really changes then you know where to start looking.

 

[boling]

Not sure it's elated or not, at Idle, I have a dancing tachometer. bouncing from 900 to 2000.

 

[boling]

*related

 

[boling]

Troubleshooting has come to a halt. My tow vehicle was rear ended on the interstate, spun across 4 lanes coming to rest against the inside concrete barrier. We are all safe. Kudos for the F150 for keeping us safe. The boat will have to wait a bit.

 

[boling]

Repaired!!! It must have been the cam roller. Took it out on the lake today, ran for several hours at different throttle settings, wot working great. Now I have a very stiff throttle. Shifting is no problem, but advancing the throttle takes way too much effort, both in forward and reverse. Time to look at the controller or cable to find out where all the resistance is coming from.

 

[oldboat1]

Disconnect cables at the motor first, and insure the shift and throttle work properly at the motor. If so, move on to the remote box and cables.

 

[boling]

Cable was the problem

 

[boling]

Replaced cable, smooth as butter. Much better than when it was new, Dealership must have done some damage to it on the install. Thanks for the help,
folks!

 

[boling]

I know this one is old, but I have good news. I replaced the power pack. It ran fine at the lake today, WOT for 8 or so miles, never skipped a beat. Thanks for all the help!!!