2001 yamaha, fs115 no upper rms

[nantucket privateer]

hello all, i just bought a 21ft privateer roamer II with a Yamaha fs115 on it, i have ran the boat 4 times, and every time the problem has gotten worse, it has no power first time i took it out it only got 4000 rpms, the second time i took it out it only got 3400 rpms then the third time 2600 rpms. in this past year we have had major problems with fuel on the island, the whole island got a bad shipment of fuel, the tank has been pumped and cleaned and i just had the fuel pump replaced, the screen on the bottom was clogged, so i took it out again and I'm back up to 3600 rmps but its still not running right, my friend (a marine mech. of 12 years) thinks the next step should be fuel injectors but i was wondering if there is any thing else i should check out.

its getting expensive real fast and i know its a boat (Break Out Another Thousand) but any suggestions would be great

 

[nantucket privateer]

Re: 2001 yamaha, fs115 no upper rms

any one????

 

[Draco]

Re: 2001 yamaha, fs115 no upper rms

I have a 2002 F115 that also dies at over 3500 rpm. (It's intermittant) I have replaced the primer bulb and the water separator, cleaned the engine- mounted fuel filter, and treated the fuel tank , and filled it (60 gal). No luck. Today I have removed the anti-syphon device at the fuel tank and it appears to be ok.
Don't think that is the problem

Before I put the boat back in the water I will replace all fuel lines from the tank and at the primer bulb.

Is there anything else I should try?

 

[99yam40]

Re: 2001 yamaha, fs115 no upper rms

Testing the fuel system pressures/vacuum will troubleshoot and tell you where to look, instead of replacing things and hoping.
replace all filters and clean/replace any screens.
Injector screens can be replaced in some or cleaned. May need to send them to a shop for testing and cleaning. But that is better than wiping out the pistons from running lean

 

[sdsaw]

Re: 2001 yamaha, fs115 no upper rms

I have a 2002 F115 that also dies at over 3500 rpm. (It's intermittant) I have replaced the primer bulb and the water separator, cleaned the engine- mounted fuel filter, and treated the fuel tank , and filled it (60 gal). No luck. Today I have removed the anti-syphon device at the fuel tank and it appears to be ok.
Don't think that is the problem

Before I put the boat back in the water I will replace all fuel lines from the tank and at the primer bulb.

Is there anything else I should try?

If your motor is shutting down like someone turned the key off, then start a new thread because I think it is not related to this problem.
The original poster is losing power but not shutting down.
If it's dying like it's running out of fuel, then it might be fuel related, otherwise it may be electrical related
I've had the shutting down problem and have some ideas for you to try.

 

[sdsaw]

Re: 2001 yamaha, fs115 no upper rms

nantucket privateer,

Yep, it sounds like you still have something clogged.
I'd suspect the injectors.
After you have them out, carefully inspect the rubber seals on both ends of them for tears or cracking.
Don't be surprised if the screen on the HP fuel pump gets re-clogged in a short amount of time if you still have some bad fuel in your system

If you don't already have one, you should have a Racor 10 micron fuel/water separator between the fuel tank and low pressure fuel pump and a Yamaha 10 micron filter between the LP pump and VST(houses the HP pump).
Hope this helps

PS: You better stop trying to run it with this problem because you may cause engine damage because of a lean fuel condition that you have.

 

[Draco]

Re: 2001 yamaha, fs115 no upper rms

Thanks for the replies and advise. The motor does not just quit running. It sort of starts to falter. If I maintain advanced throttle it will die. If I throttle back motor will continue to run.. I suspect some or all the little filters on the engine as you suggested. Will try all and report.