Suzuki 115 4 stroke feels like not enough fuel under load @ over 2000 rpm

[Panama Tom]

I have a problem with the engine sputtering and backfiring at about 2k RPM and higher. This started happening after the boat sat for about 3 weeks. We got about 10 gallons of gas with e10 from the station on the way to the ramp. When we started it up and idled it around for about 10 minutes so it was warmed up (we changed the oil and filter and the fuel / water filter, also the filter going into the engine at the bulb).

When we tried to throttle up it started to bog down and cough and sputter. Put it back on the trailer, went home and then I started to read the forums. I have since taken out about a pint of water from the tank (pumped it through the separator and back into the tank) then I put a bottle of HEAT in the tank. Kept emptying the separator and checking for any residual water. I did this for a couple of days and also changed the fuel /water seperator to one that has a clear bottom and drain plug. no water showing up for the last couple of days.

I called the Suzuki dealer and he said to change the plugs I did that. I also tried to put it in gear and bring up the rpm to 2 -3 k but without a load don't want to go any higher and it runs fine.

I bought a fuel pressure gauge and checked the fuel pressure at the low pressure pump about 3-5 lbs and at the fuel rail about 33-35 lbs and when you turn off the motor it goes down to about 25 lbs. and stays there for a while. When I tried running the rpm up to 3k again the pressure stays stable but I only held it up for about 30 seconds.

Does any one have any ideas what else I can try? It sort of sounds like a timing issue because it still has good fuel pressure, but the Selloc manual is a little confusing when it comes to timing advance.

Thanks in advance for your help. Whenever I have had a problem in the past you guys have been able to lead me in the right direction.

Panama Tom

 

[99yam40]

Re: Suzuki 115 4 stroke feels like not enough fuel under load @ over 2000 rpm

water in a tank with E10 kills the octane.
I would drain and clean the tank

Try running on a portable tank with fresh fuel

Make sure the alarm system is functioning

find out what the specs are for the fuel rail pressure
not sure if 35 would be correct

 

[crb478]

Re: Suzuki 115 4 stroke feels like not enough fuel under load @ over 2000 rpm

Sound like your injectors may be clogged. I had something similar happen on a 90 hp Yamaha four stroke. It would run at lower rpms but not power up. It had fine grit in the filter directly before the injectors. I got new spark plugs same thing. Sent the injectors off to be cleaned and it ran like new again. Was told that the E10 is a great gas tank cleaner and will loosen up all particles down the line from the motor. The tinniest particles will pass through all your filters but not the injectors. I ended up cleaning the gas tank the best I could, its built in, Adding a new fuel line from the tank to a new 10 micron filter, new primer bulb and line, and new filter on the motor to try to get rid of any particles that may be in the system. Cleaning the injectors only cost about $80.00

 

[Panama Tom]

Re: Suzuki 115 4 stroke feels like not enough fuel under load @ over 2000 rpm

That's what I did today. I took all of the fuel out of the tank and then cleaned the separator/filter and the inline filter right after the priming bulb and ran out of a 5 gal can of NON E-10 gas. put it in the water and ran a little till it warmed up then started to give it some throttle, went fine up to about 2500 RPM then the fuel pressure started to dip down to about 20-25 LBS. and started to bog down. I read in one of the other posts that 35LBS. is about right. that was enough for me. I called the dealer who said it should be around 39 LBS. and that it sounded like it was in the VST or at worse the fuel pump might be going bad. I dropped off the boat and he will check it out.

Thanks 99yam40 and crb478 for your suggestions I will update this post when I get new$ :greedy_dollars:

 

[Wurzle]

I HAVE HAD TWO HEADS CRACK BECAUSE OF WATER IN THE FUEL. You need to drain the injector pump and the injector rail too. The aluminium bar to the injectors. I hope its not too late for you. One engine was a df 250 and it got water in the oil when the head cracked. The other was a 140 that had water in two pistons. I only found out what the problem was when I could not remove a spark plug. It was corroded in due to salt water. I had to remove the head.