Fuel Pump Questions - Yamaha

[hotajax]

Engine slows down just after startup, and sometimes idles down to 400-500 rpms and occasionally stalls out. I have decided to do something about the fuel pumps. Before I buy 3 new pumps, is it worthwhile to replace the diaphragms or just replace the whole pump? There are three pumps. The boat is 12 years old, and to my knowledge the fuel pumps have never been replaced. Other questions - What about increasing the idle speed? Or is this a case of what made the idle drop down in the first place?

 

[seasick]

I had a similar issue on my 2001 sx150. When first started the motor runs fine for a minute or so. It then slows down, eventually sputtering and stalling. After that it runs fine all day.
It is not the VST, filters, plugs, thermo switches, thermo sensor or O2. All tested OK. Pumping the primer bulb when the motor slows down does not stop it from stalling and that makes me think it isn't fuel starvation. There is no excessive smoke and that makes me think that it isn't too rich a mixture either.

I pulled and tested one LP pump and it appeared to be OK. At least is want leaking on the back as folks mentioned. I didn't test the second pump since I have to unbolt the VST to get at the LP pump bolts.
So after many months of head scratching, I decided to raise the idle as the motor started to slow down. I expected that would raise the normal warmed up idle speed but it didn't. It just stopped the motor from stalling. It has been like that for a few months. I really don't understand what is going on and will do more in-depth testing in the off season but for now raising the idle 'fixed' the problem.
Let me know what you find out.

 

[hotajax]

That was a helpful post, thanks.
H. A.

 

[gw204]

Just replace them. After I replaced the pumps on my old 225s, I tried to break one down just to get a look at it and couldn't get it to open up.

I think the diaphram kits are almost as expensive as new pumps. Two zip ties and two bolts (10mm heads I think) on each. It's a piece of cake.

 

[kmhitecman]

those motors like too sneeze on cold startup most of the time it it is center fuel pump that goes change all three pumps. u can test them by losening them up a little with a 10mm socket and wreanch pull pump away from block a little pump primer blub see if gas comes out pluse hole in back of pump. no gas should come out of hole. you will see a little gas leak around the 3 phillps screws when u do this test but that is alright. u have to losen bolts for vst tank but u due not have to remove them . then with 10 mm wreanch u can get to bolt behind vst tank to losen up one bolt. then test.

 

[westar]

I have a 150 OX66 - TXRY and it's beginning to do the same thing. Approximately how much is a fuel pump (without labor fees) for this engine?

 

[kmhitecman]

ABOUT 42.00 BUCKS U HAVE TWO ON THAT MOTOR

 

[Zebulon]

Bought 6 LP Pump Kits @ around $42.00 / ea from SIM Yamaha, received them today and will install tomorrow hopefully. The only issue I had was a gas slick around the stern of the boat while flushing the motors after use. Motors ran fine @ all RPM's, was told a faulty pump would dump excess fuel into the crankcase and may cause them to run too lean. Said you should replace every three to four years, motors are 2000's and I'm the third owner and not sure of the service history. Will let you know how I make out and if it cures the problem.

 

[kmhitecman]

IF YOUR MOTOR RAN FINE AND DID NOT STALL AT SLOW SPEED YOUR FUEL PUMPS MIGHT NOT BE BAD. BUT R FINE TO CHANGE SO U KNOW THEY R GOOD. U MIGHT HAVE ATRIM LEAK IT MIGHT BE OIL ON WATER WHEN U FLUSH MOTOR.