yamaha 225hp runs well for hour or two then slowly dieing

[sonic NZ]

My Yamaha excel 1986 225hp v6 runs fine with awesome power for the first hour or two depending on water conditions then it starts losing power gradually for the next half hour until it eventually stops. the odd thing is when it does stop (with full throttle) and after the throttle is placed back into neutral . . . it starts without a missed beat and will idle all day long, but when throttle is given it stops instantly , then if I take it out the next day it would do the same thing one to two hours running then nothing.

It has only just started doing it. the only thing that has changed would be the water pump pressure dropping, but the temp gauge says it not over heating. any help would be great help ... thanks.............Matt

engine details : 225AETO 6K7 UL 701420

 

[Les MacDougall]

Re: yamaha 225hp runs well for hour or two then slowly dieing

If you run it hard does it cut out sooner?

Les

 

[sonic NZ]

Re: yamaha 225hp runs well for hour or two then slowly dieing

absolutely, If I'm towing or conditions are choppy she will last only an hour, if its flat and taking my time she will last maybe two or more hours but once it starts losing power it doesn't gain power unless i stop for ...... maybe three or four hours

 

[pine island fred]

Re: yamaha 225hp runs well for hour or two then slowly dieing

Finger filter/screen inside your gas pick up tube is probably clogging up. If so equiped. Remove the tube, take off the anti-siphon valve, push the screen up out of the tube from the bottom with a smaller diameter copper tube or long wooden dowel. I would leave it out and rely on the main fuel filter. regards FRED

 

[sonic NZ]

Re: yamaha 225hp runs well for hour or two then slowly dieing

I have a large water fuel separating filter very close to the fuel tank (built into hull of boat) and then a much smaller filter inside the engine itself which is see through. Is one of these filters the one you a meaning or is there anther one on the fuel line somewhere?

I would hate to unnecessarily change filters due to the cost of them here in NZ is there a way to test them . . . . fuel seams to flow freely into the fuel bowls when squeezing the fuel primer

 

[cousinabe]

Re: yamaha 225hp runs well for hour or two then slowly dieing

Sonic,
When your condition occurs, did you happen to notice if the primer bulb is collapsed?
If so, this would indicate a fuel restriction issue which could be related to:
1) clogged fuel tank vent. Test by removing fuel cap to see if it goes away.
2) clogged pickup tube as fred mentioned.
3) clogged anti-siphon valve.

If the primer bulb is not collapsed, can you pump it during your power loss and report any results.

 

[sonic NZ]

Re: yamaha 225hp runs well for hour or two then slowly dieing

that was the first thing that came to mind when it first happened - a lack of fuel - so when I attempted to prime more into the carburetor bowls I couldn't . . . . . the primer bulb was rock solid of fuel.

The smaller see through filter on the engine comes after the fuel primer, if this was clogged the primer bulb wouldn't collapse, I will bypass this filter today and see what happens.

thanks

 

[rodbolt]

Re: yamaha 225hp runs well for hour or two then slowly dieing

when you bypass that filter and allow all that trash to the carbs please start a new thread about clogged carbs.
dumbest post I can remember.
mmmmmmm my filter is clogged let me bypass it and see where the trash goes?
slow down, think.
it runs fine until choppy or a hard load is applied.
and choopy adds tremendous load and stirs the fuel.
what would it hurt to use a simple vacum guage t'd into the system at the lower lift pump intake?
takes almost no time.
if fuel system vacum exceeds 4"Hg at any RPM you have a restriction, if not check/replace the pump diaphrams as 3 years is typical life span.
from there its less than 2 hours and 3 fuel bowl gaskets and possibly 6 main jet orings to dissasemble,clean and reassemble the carbs.
if you suspect electical, and I dont, monitoer high speed charge coil output voltage.
but your describing a fuel problem try not to make it worse.
the filter on the engine on that model is washable.

 

[pine island fred]

Re: yamaha 225hp runs well for hour or two then slowly dieing

The finger filter I am talking about is actually in the fuel pick up tube in the fuel tank. Cone shaped, could be 4 ins. long made of a copper material. It is the first in line, picks up bugs, bark, leaves, hair, all sorts of trash that somehow makes it into the fuel tank.
Years ago, GM thought it was a good idea and actually had what was refered to as a tea bag filter in the fuel tank. Big fix was to blast it off with compressed air back thru the fuel line. There was no elect. pump in the tank at that time. regards FRED

 

[sonic NZ]

Re: yamaha 225hp runs well for hour or two then slowly dieing

I have now removed the small filter from inside the motor and bypassed it. I replaced the large fuel/water separating filter with a standard fuel filter but while I had all the filters off I flushed all the fuel lines between the six carburetors and main fuel tank (so no fuel got to the motor without passing the new fuel filter) I flushed maybe 2 leters into my quad bike.

The other filter located in the fuel tank . . . . . can this be knocked out hmmmm will give it a go.

. .
. .
. . . . nope I cant remove the filter from inside the fuel tank if there is one

- I removed the fuel line and brass adapter only to find a screwdriver would only make it about a quarter of an inch of the way in (i think there is another adapter on the inside).

The fuel line exits from the top of the fuel tank so I am to assume there is a fuel line inside the fuel tank leading to the bottom.

 

[pine island fred]

Re: yamaha 225hp runs well for hour or two then slowly dieing

OK, reconnect the fuel filter on the motor. Remove the fuel pickup tube from the tank. From the bottom of the tank pickup, insert a long tube or wood dowel and push the finger filter out of the TOP of the pickup tube. It is copper mesh, cone shaped, should pop out. FRED

 

[sonic NZ]

Re: yamaha 225hp runs well for hour or two then slowly dieing

I would love to but there is no way into my fuel tank, its built into the hull of my boat, the only thing on the fuel tank I can get to is the exiting fuel line to the engine and the refill fuel line, both are on top of the fuel tank.

the priming fuel bulb is not collapsed when the engine trouble happens, doesn't this indicate sufficient fuel is reaching the primer thus fuel is passing the fuel tank filter if there is one?

 

[pine island fred]

Re: yamaha 225hp runs well for hour or two then slowly dieing

I am really just guessing here. My first thought is to substitute an alternate fuel supply but with that size motor you would need more than a 5 gallon ( 20 lieter + ??? ) portable tank. You mentioned that you could only get a screw driver a short distance down the fuel pickup. Am assuming you had the anti-siphon valve removed and was looking down the fuel pickup tube. Push the screw driver down slightly, twist and try to grab the screen. It should pull right out.
Wish I could be more help with the primer bulb thing. I never have to prime my 4 stroke. If my 50 2 stroke is running I am always able to give it a squeez or 2. Never gave it much thought. regards FRED

 

[pine island fred]

Re: yamaha 225hp runs well for hour or two then slowly dieing

Just occured to me. Portable tank, top it off periodically to get your hour running time. See what happens. FRED

 

[sonic NZ]

Re: yamaha 225hp runs well for hour or two then slowly dieing

all is well since filters have been replaced must have been a fuel shortage due to filter blockage..


but now I have another problem........
when the engine starts warming up it starts miss firing
you can hear and see the motor drop RPM for a moment until the throttle is raised..... then it sounds and looks fine but will only give 75kph instead of 105kpm.

I have started a new post for this problem, if you think you understand help would be greatfull

THANK YOU all so very much for your help




Matt
and Sonic (the boat)

 

[rodbolt]

Re: yamaha 225hp runs well for hour or two then slowly dieing

dang I am good. I predicted this one
but ill go look.