yamaha 9.9 hp cutting out

[dogsbollox0]

recently purchased a boat with a 2001 yamaha 9.9 hp 4 stroke ouboard on her ,took her out for the first<br />time cruised for approx 4 hrs no probs,second time out cruised for about 2 hrs no probs until we did a u turn on river and she cut out ,i thought it was because the fuel tank was just over the quarter she might<br />need refuelling but after refuelling she would run and then cut out after any amount of time ,i have replaced fuel line and bulb from tank checked small<br />filter in fuel line,but even after this she will play up running for a few minutes then cutting out<br />dead ,after doing this 4 or five times she might run for 3 hrs,engine does not seem to splutter when she dies you just hear a slight hesitation ,if i can squeeze the bulb quick enough she will keep running .<br />any ideas please

 

[rodbolt]

Re: yamaha 9.9 hp cutting out

hello<br /> I would start by at least draining the carb. maybe even removing it for cleaning. also test the fuel pump. its a quik easy test. the cut out at a sudden change in direction may indicate it picked up some water or trash and passed it on to the carb,by the fact you can keep it running by hitting the primer bulb indicates the possibility of something other than gasoline, petrol, in the fuel bowl. but without hearing the cutout its hard to tell. all I can go by is the clues you give.

 

[garyN]

Re: yamaha 9.9 hp cutting out

Hi<br /><br />I had very similar problem with the same year Yamaha 4 stroke Hight Thrust. At the end of the day it turned out to be two items:<br /><br />1. the fuel pump had a crack on the diaphram. Yamaha replaced it - also note that it had been redesigned to route the water cooling,<br /><br />2. the carb was replaced and it had also been redesigned some. these carbs are expensive, so dont do that unless you ahve a warranty.<br /><br />Hope this helps<br /><br />Gary N

 

[garyN]

Re: yamaha 9.9 hp cutting out

To clarify<br /><br />The fuel pump is now cooled by the water pump indicator hose to (according the the Yamaha factory rep) avoid vapor lock. <br /><br />As for the carb they have issues. Look to see if you have oil dripping from the front. If so I'll bet you fuel pump is bad. Also check your oil - if the level is up (or over full) see if it is diluted. this can happen with the bad fuel pump. <br /><br />Look for oil on the plugs also since, if you oil pump diaphram is cracked your engine is burning a mikture of oil and gas like a two stroke! and the plugs are likely black with a oil film.<br /> <br /><br />Good luck, nice engine when it runs well.

 

[dogsbollox0]

Re: yamaha 9.9 hp cutting out

Hi rodbolt,<br />you say to check fuel pump its quick and easy,<br />could you please give details.<br />thank you

 

[rodbolt]

Re: yamaha 9.9 hp cutting out

dogs<br /> use a vacum gauge and test as per the service manual. or you can use a pressure gauge and pressurize it to about 5 psi, pressurize the inlet side with the outlet side capped. should hold 5 psi indefinatly. then try to draw a vacum on the inlet side. should hold. the check valves will only allow a one way fuel flow. most of GaryN previous problem was a fuel issue compounded by incompetent techs, in my opinion. but usually when it works great then after some high G force manuvers it does not you will find water or debris in the carb. happens a lot.<br /> the caarbs have no issues that I am aware of other than the passages are very small and very susceptable to debris.

 

[bigbrownbuku]

Re: yamaha 9.9 hp cutting out

biggest problem i see by far is debris in those carbs. otherwise they run fine. the low speed pickup is 1 of the smallest holes you could get light through, a hair will make it run poorly.<br />a good filter would certainly help.

 

[garyN]

Re: yamaha 9.9 hp cutting out

Rodbolt is corret, my problem was bad service - but the problem was just like your and the small crack in the diaphram seemed to act up only at certain RPM's?<br /><br />As for the Carbs - I have had 3 replacements mainly because it is easier to put a new one on than clean the little holes and jets.<br /><br />I would do whatever Rodbolt advises to test your pump - and I would take it apart and look at it - the crack in mine could be seen (it was on the rolled edge, almost on the very circumfrance of the material.<br /><br />Good luck

 

[dogsbollox0]

Re: yamaha 9.9 hp cutting out

Thanks for the info rodbolt cant seem to find a four<br />stroke workshop manual that covers my year of engine,<br />latest manual i can find is 1985-1999 is there much<br />change on the later engine?

 

[bigbrownbuku]

Re: yamaha 9.9 hp cutting out

find the genuine yamaha manual if you can dogsbollox. its written differently but its a far better manual.

 

[garyN]

Re: yamaha 9.9 hp cutting out

One additional suggestion. Check your fuel tank - I have had the pick up tube blocked by a smal piece of paper or plastic. IN the old tanks it was rust. anyhow, they would run fine unit this piece got stuck on the screen of the pick up tube - then stop and often restart and run fine. You can take the tube out by unscrewing the part on the tank that holds the fuel joint. Lift it out and inspect it and the bottom of the tank. If you see any dirt or foreign objects dispose of the gas property and start with fresh.<br /><br />Gary N