2018 20VTX Engine bogged down, maxed RPM @3000 with full throttle

[BillR]

Have had an intermittent issue with engine bogged down, at full throttle, barely got up to 3000 rpm, with ballasts full surfing.....happened 2x last summer and again twice this last summer with passengers 3-7 in total.  Someone suggested I run the boat at full throttle at top speed with empty ballasts for several minutes.  Sure enough it cleared it out and engine runs fine after doing it.  

Has anyone experienced this? What does running top speed do to fix it? What causes the bogging down? Is it a computer issue....much like a PC needs to be shutdown and restart to clear cache or RAM?

Bill R

[Pie]

Since this only happens a couple of times a season I'm inclined to say you may be over propped for the load. When running with heavy load and close to the motor capacity, fuel injection dumps more fuel creating a rich mixture.

By running it at WOT without the load, you're giving it the old Italian tune up, basically clearing the carbon from the motor and exhaust.

When surfing with the load, note the RPM and then give it the beans all the way. Note the maximum RPM. How much more were you able to rev?

Was the engine happy to give more?

 

 

[oldjeep]

If I were to guess, I would say you have either completely fouled your o2 sensors or cooked the cats.  Since it cleans up, I will go with o2 sensors.  Re-prop the boat for chugging overloaded so that you can get the RPMs up into the powerband during your normal activity.

Edited October 15, 2023 by oldjeep

[justgary]

@Engine Nut said it best:

 

[BillR]

On 10/15/2023 at 5:54 AM, Pie said:

Since this only happens a couple of times a season I'm inclined to say you may be over propped for the load. When running with heavy load and close to the motor capacity, fuel injection dumps more fuel creating a rich mixture.

By running it at WOT without the load, you're giving it the old Italian tune up, basically clearing the carbon from the motor and exhaust.

When surfing with the load, note the RPM and then give it the beans all the way. Note the maximum RPM. How much more were you able to rev?

Was the engine happy to give more?

 

 

Thank you....sorry for the late response....was traveling.  When surfing with a load....the engine happily gave more power/rpms to about 4800...of course with more groan....btw what did you mean "over propped for the load"?...

[BillR]

Just now, BillR said:

Thank you....sorry for the late response....was traveling.  When surfing with a load....the engine happily gave more power/rpms to about 4800...of course with more groan....btw what did you mean "over propped for the load"?...

Also, I'm inclined to accept your thought of carbon build up...and running WOT clears things up.  Thanks again

[BillR]

On 10/15/2023 at 1:43 PM, oldjeep said:

If I were to guess, I would say you have either completely fouled your o2 sensors or cooked the cats.  Since it cleans up, I will go with o2 sensors.  Re-prop the boat for chugging overloaded so that you can get the RPMs up into the powerband during your normal activity.

Forgive me for this dumb question....what do you mean by re-prop the boat?

[oldjeep]

2 minutes ago, BillR said:

Forgive me for this dumb question....what do you mean by re-prop the boat?

Take prop off, put a different one on that is more suited to your activities.  If you tell folks what prop you currently have on, they should give some suggestions on what might work better for surfing.

[BillR]

On 10/27/2023 at 10:50 PM, oldjeep said:

Take prop off, put a different one on that is more suited to your activities.  If you tell folks what prop you currently have on, they should give some suggestions on what might work better for surfing.

Thank you