'77 9.9 surging at WOT

[chris in va]

Finally took my 9.9 out yesterday and after spending 10 minutes trying to start, it finally decided to go after the right combination of levers and knobs.<br /><br />Once on the water it ran great! Even the guy at the boat rental store said it was faster than most 9.9's he's seen (15hp carb). But after about 10 minutes of WOT, it started chopping power somewhat...and I can tell this was fuel related. If I backed it down to 3/4 throttle it ran smoothly again but once I broght the boat off plane and back to idle it stalled instantly. Couple squeezes of the bulb and started right back up again.<br /><br />Now, to fix a bogging issue earlier I had to bend the float valve plate up some. Could I have done it a hair too much? Also the rebuild kit came with this little spring for the inlet needle. Should that be on there?

 

[Xcusme]

Re: '77 9.9 surging at WOT

Chris, a couple of things. <br />Carb clean/ rebuilt??<br />Float level parallel with carb body in inverted position?<br />Did you try squeezing primer bulb when you lost WOT, did RPMs pick back up?<br />Was motor running hot? When was impeller replaced last?<br />Inlet needle spring insures that needle will open when float drops.<br />Fuel lines secure, no air leaks.<br />As a last resort, try running WOT with cowling off, perhaps an exhaust/powerhead gasket leak is choking motor with exhaust fumes.

 

[chris in va]

Re: '77 9.9 surging at WOT

Carb has fresh rebuild.<br />Float was leveled, but caused the flooding problem so I bent it slightly up and it ran after that.<br />Squeezing the bulb didn't do anything.<br />Brand-new water pump. Pisser was going strong.<br />Fuel lines are new, along with the fuel pump.<br /><br />Looks like I need to put the spring on after all. When I installed it the first time, it didn't appear the needle would open fully. I guess it just has to clear the rubber tip to get gas, right? Could very well be the inlet needle is getting stuck closed.

 

[Xcusme]

Re: '77 9.9 surging at WOT

Originally posted by chris in va:<br /> Looks like I need to put the spring on after all. When I installed it the first time, it didn't appear the needle would open fully. I guess it just has to clear the rubber tip to get gas, right? Could very well be the inlet needle is getting stuck closed.

Right, the rubber tip seals off the fuel flow. If the needle sticks in the seat, it would be hit or miss to open as the float drops. When you install the spring, inspect the tip of the needle for any damage. Replacement needle seats are available too. The needle and float arm should move smoothly and in unison. If you invert the carb and glently blow into the fuel line inlet, the weight of the float should seal the needle.

 

[chris in va]

Re: '77 9.9 surging at WOT

Ok, thanks. I did notice the inlet needle would not always drop down immediately with the float plate, at least not smoothly. I asked the guy at the parts counter about this and he said if the original carb didn't come with the spring to not worry about it.<br /><br />Now I'm gonna 'worry' about it!

 

[OBJ]

Re: '77 9.9 surging at WOT

Chris, just to add to X's good advice, check the drop on the float. Should hang 1 1/8 to 1 3/8" when the carb is held right side up....measure from the bowl gasket surface to the bottom edge of the float....front side.

 

[chris in va]

Re: '77 9.9 surging at WOT

Yup, that cured it. Luckily the old 9.9 carb still had the spring in place, along with a better plastic float so I just scavenged parts for the 15hp carb. It runs *nice* now. No more surging.<br /><br />Just curious, how many pulls should it take to get this thing started? Before my pull starter blew up, it was taking about 12-15 before it finally coughed. My right arm is gonna be MUCH larger than the left because of this.

 

[OBJ]

Re: '77 9.9 surging at WOT

If the ignition system is good and the carb is set right, 2 to 3 pulls should have the engine running......this is from a cold start....choke out, couple pulls and engine coughs or starts...choke in engine running or another pull to get it going.

 

[chris in va]

Re: '77 9.9 surging at WOT

Thanks for the info. This is my first pull start 2-stroke, and I'm somewhat clueless on the procedure. <br /><br />The 5hp 4 stroke takes 2 pulls usually...if that.