2011 Suzuki 140 bogging and surging intermittent issue

[The Riddler]

Been battling an intermittent bogging and surging issue in my 2011 140. Today I took apart the vst and replaced the filter and cleaned. Came back tonight after running it for an hour. You can run it in reverse to 5 rpm or more and have no issues. Going forward you can run from 5-6 rpm and it comes back and reduces to 3.5-4rpms. Checking reverse again, it fine, going forward can't get above 3.5-4rpms with throttle all the way. Shut off and start up a few times and it goes away and you get back to the ramp with no issues. Checking neutral, will not rev above 3. That. Seems to be on par. Cannot figure out what the issue is only going forward. Was thinking it may be neutral switch but works fine in reverse.

Any help will be appreciated.

[Moonlighter]

Neutral throttle switch on engine prevents the engine being revved past 3000rpm in neutral. Sounds like its working as it should on yours.

So, seriously, you have put the engine into reverse, boat in the water, and run it up to near max rpm for several minutes??? That must have been interesting!!

Apart from cleaning the vst, what else have you done to try to find the issue?

How long since you changed spark plugs? Engine reducing revs like that is suggestive of a cylinder dropping - spark plug failure after getting hot/under load….

Do you have a inline water separating filter eg RACOR style filter on the fuel line?

[The Riddler]

Yes. Have the racor with clear bowl and clean out. Emptied that a few times. Plugs are just over a season old. I have another set will swap and take her out. I will take a look at ignition coils. Thanks.

I have a scupper boat. Northcoast 20. Yap, there was some water in there going reverse.

[artdf175]

two things come to mind
fuel? have you checked the condition of the fuel bulb?
If it is all sucked in you are having a fuel restriction
the other issue I have been dealing with myself is electrical
is the engine throwing any codes?
I narrowed my problem to bad connection with the rpm sensor.
put the engine interface on the screen and was running along just fine then the RPM's jumped off the top to zero and back.. the engine would go from say 5000 Rpm to 4100 rpm and there was nothin do to get back to 5,000 other than shut down and restart.
then found the problem in the SDS connector.
Art

[The Riddler]

Fuel bulb good. I do not know if the engine is throwing codes. No light is on and do not have software.

[The Riddler]

I will locate the rpm sensor and inspect. Thanks.

[The Riddler]

two things come to mind
fuel? have you checked the condition of the fuel bulb?
If it is all sucked in you are having a fuel restriction
the other issue I have been dealing with myself is electrical
is the engine throwing any codes?
I narrowed my problem to bad connection with the rpm sensor.
put the engine interface on the screen and was running along just fine then the RPM's jumped off the top to zero and back.. the engine would go from say 5000 Rpm to 4100 rpm and there was nothin do to get back to 5,000 other than shut down and restart.
then found the problem in the SDS connector.
Art

Art, having trouble locating rpm sensor. Can't find anything tagged that. Maybe one of these?


51AFB4BF-DE1A-4B92-9D17-0B6A32F78064.png

[artdf175]

It is the CKP sensor
it is located wonder the flywheel

[The Riddler]

It is the CKP sensor
it is located wonder the flywheel

Thank you . Appreciate it!

[The Riddler]

Changed out the spark plugs and ran good tonight with no bog down. Will keep an eye on it and report back. To me the plugs looked fine, more wear on one than the other but not bad. Plugs were last changed 14 months ago accord to my log.

Thanks for your help guys!