Rpm fluctuations

[Seacraft12]

I tried to post earlier but I can't find it now. 2001 115 two stroke TXRZ. It will run fine at 3900 rpms. If I push above that to include up to WOT the rpms fluctuate a lot rapidly and you can feel and hear the engine surge and bog as the rpms go up and down. This is the second trip like this and have not experienced this before. There was a little water in the racor bowl which was drained and the plugs have been changed after the first trip but the problem persists. Please help. Thank you.

[rodbolt17]

more than likely you waited 2 minutes to long on changing the filters.
most likely now you get to clean carbs,flush lines and replace the lift pump.

[Seacraft12]

Thanks rodbolt. Will do. Does the lift pump refer to the fuel pump or is it something else? My service manual is at work of course.

[rodbolt17]

lift pump,fuel pump.
I don't rebuild them as they are about 50 bucks new.

[Seacraft12]

Okay thanks. I actually replaced the fuel pump a few months ago just beacause, so I have the one that was installed previously. I took that one apart to see how it worked and was surprised it was just a membrane looking thing on the inside. I put it back together and put it in my spare parts drawer. Do you think it would be okay to use or should I even bother replacing since I did just a few months ago? Also, I replace the racor filter a month ago but not since there was a little water in the bowl and the small engine filter was replaced 1.5 months ago. Should I still change them? Thank you.

[TownsendsFJR1300]

Did you empty the Yamaha under cowl fuel filter?

If its just water, you may get by just draining the carb bowls. Prime the primer bulb until clean fuel comes out...

Put a small CLEAN tuna fish can under the drain bolts and catch what comes out. If there's water there, it'll show as cloudy and separate...

[Seacraft12]

Thanks guys I will try all this after the hurricane/stiff breeze passes. Rodbolt, still think I should change the filters that were changed very recently? Thanks

[99yam40]

You did notice Rod is in NC

Filters will plug if you throw nasty stuff through it

So it depends on what you have in the fuel system

[rodbolt17]

I spent ALL yesterday after 12 moving stuff.
I spent MOST today moving it back.
hurricanes suck but other than 3 pieces of siding I did good this time.
actually got to party a bit this afternoon.
gonna go full on tomorrow.

but getting back to the issue.
all I can say is if you rebuild and clean the fuel system at breakfast and all is well.

at lunch you reintroduce debris.
guess what's for dinner?

[99yam40]

if there is water in filter then it is a very good chance you need to be getting the water out of the tank, lines,pump, and carbs.

Rod has said before when he cleans carbs he replaces pumps, filters, and flushes lines just to keep anything in then from hitting the cleaned carbs and coming back to him.

Cleaning the tank, carbs, and filter/screen on motor along with flushing the pump and lines should be enough. If not you get to try again

[Seacraft12]

So far I have replaced the racor, cleaned the small engine filter(hardly anything there), removed carbs, disassembled them completely and have one soaking in carb cleaner. With the carbs out I pumped the ball several times and collected the fuel that came out of the lines. It appears very clean but I will do it again to ensure it was not just the clean fuel I put in the racor filter. Then I have to figure out where my water is coming from. I suspect there are only two places as the tank is brand new last year. The fill or vent. I will replace the fill with a new one to be sure. Anything else? Thanks again guys for all your help!!

[TownsendsFJR1300]

If you have the carbs off, pull the jets and visually inspect them to make sure their clear. Just blowing carb cleaner and air may NOT clean the jets. Soem jets have HORIZONTAL holes you cannot see unless you pull the jet from the car body.

BTW, the jets are the first thing to varnish and clog up, especially if not using a fuel stabilizer. Once cleaned up and running right, Yamaha's Ringfree will help keep them that way..

Cleaned 3 carbs last week (small engines, two mowers, one larger CAT pressure washer), ALL clogged jets... A fourth engine, just water in the bowl-(along with a cameleon in the tank, yes a cameleon) commercially used.

[Seacraft12]

Thanks guys. I totally dismantled the carbs as far down as the could go soaked in a gallon of carb cleaner than used the spray carb cleaner and finally compressed air. Reinstalled everything, replaced fuel pump, filters and flushed the lines. Just did a quick (20 min) sea trial and everything is top notch!! Thanks for all the help now on to my source of water... I'll be replacing the fuel fill and try that.