problem on the water today

[CAM212SS]

every thing was going just fine... Pre launch checks etc.
launched the boat. everything seemed normal
once we got out of no wake zone, I hit the throttles and noticed my port engine would only go to 4200 rpm
i stopped to make sure there was nothing around the impeller, checked the throttle wire etc.

do you think i have a fuel filter issue clogging the line not letting it go past 4200 rpm
everything up until 4200 is normal feeling and sounding on the engine

 

[CAM212SS]

things get more strange to me anyhow...
i got the boat home and hooked it up to the hose... Now everything seems fine. Would make a difference if it is not under load to allow the RPM's to be normal again or do you think it was a water issue in the line and it finally passed.
I always use 100% gas and fuel stabilizer every tank

 

[Chuckbig]

Spark plug failure maybe?

 

[CAM212SS]

engine felt smooth even when it was stuck at 4200... would spark plugs cause it not to rev to full rpm ? but now being home it revs to full RPM
i did not change the plugs this year, but since owning a jetboat from 2011 i have changed them out yearly.

 

[4x15mph]

Out of water can be very different than under load. I wouldn't rev it much past 4000 on a hose anyway so you want to be back in the water for testing.

How does the air filter look? How do the spark plugs look?

Not sure what your overheat rev limiter is but on my boat if I have an overheating situation, the engine does not rev past 3500. Be on the look out for overheating as another cause

Others will have ideas but I would start with the above ideas

 

[CAM212SS]

water coming out of pee holes just fine while i was idling out and also when pushing the throttles up. once we got past no wake zone and i throttled up was the first sign of rpm issue... no sign of overheating from the gauges. Would under load prohibit a higher RPM than on the hose ?

 

[mark_m]

I forgot to plug in one of the coils after spark plug change. Maybe you are running on 3 cylinders on the port side?

 

[skrip345]

water coming out of pee holes just fine while i was idling out and also when pushing the throttles up. once we got past no wake zone and i throttled up was the first sign of rpm issue... no sign of overheating from the gauges. Would under load prohibit a higher RPM than on the hose ?

Yes, most definetly. On the hose, it could potentially rev to red line (or higher, so be careful, theyre not designed to be run hard out of water) and then not make enough power to over come the load once in the water. I would carefully inspect the intakes, props, pumps, etc first. Then move on to oil level, air filter, spark plugs, etc.

 

[Murf'n'surf]

I'm going to guess that you had some debris in that impeller to cause cavition that you couldn't hear with the other engine running up in rpm. Unless you throttled it fully without the other engine.

 

[buckbuck]

I will suggest you look at the throttle linkage and make sure the keeper nuts are tight and the throttle rotates to the stops.

 

[CAM212SS]

I forgot to plug in one of the coils after spark plug change. Maybe you are running on 3 cylinders on the port side?[/QUOTE




The strange thing to all of this is that everything was perfect 4 weeks ago

 

[CAM212SS]

I'm going to guess that you had some debris in that impeller to cause cavition that you couldn't hear with the other engine running up in rpm. Unless you throttled it fully without the other engine.

it did not seem to be cavitation, and i did just keep the other engine at idle speed when pushing the rpm's up on the one i am having issues with

 

[Scottintexas]

one year I had an engine that would only go to 7k rpm's, I changed the plugs and everything was back to normal,

I'd test it on the water again and then start with the plugs,

 

[jwhedberg]

Murf n Surf is probably right, there is (or was) some debris still stuck hiding in your impeller or your intake grate. While there are other possibilities as cited above, after over two decades of jetboating, a tiny woodchip or rock or other small piece of debris has been my problem 9 out of ten times, even after inspecting the intake grate and impeller carefully.

 

[Scottintexas]

when was the last time it ran right? last week or last year?

 

[CAM212SS]

4 weeks ago... no issue....
i am changing the spark plugs now. I have added some insulation and did notice that some of the insulation got close to the air intake... could that be the problem. it not getting enough air for the amount of fuel it was asking for and keeping the rpm's lower ? i wont be able to get back on the water till thursday next week to know for sure

 

[Murf'n'surf]

4 weeks ago... no issue....
i am changing the spark plugs now. I have added some insulation and did notice that some of the insulation got close to the air intake... could that be the problem. it not getting enough air for the amount of fuel it was asking for and keeping the rpm's lower ? i wont be able to get back on the water till thursday next week to know for sure

Time to call in sick and head out Monday

 

[CAM212SS]

Time to call in sick and head out Monday

that sounds like a good idea LOL

 

[Matt Phillips]

In addition to your plug change, I suggest carefully running your finger along each impeller blade runs next to the wall... See if you CERN feel any debris. Also check along the entire length of the drive shaft... Maybe there is some thing wrapped around it.

 

[rkluck]

The few times I had issues like this typically was something causing cavitation or spark plugs. There are several treads on spark plugs but I just changed them every year to insure no problems. Many times the cavitation problem would go away after reversing a few times or even just the next day. I thought maybe the stick or whatever got softer (or maybe dried and more brittle) so it would break and get pushed through.