yamaha 225 year 2002 losing power

L

Lucky Tiger

Member
my engine is bogging down when you pin it or throttle up. if you carefully creep the throttle up it can reach 5200 rpm when it used to get 6000. i have changed all plugs, fuel filters, squeeze ball, checked for air locks, tried pumping the ball when bogging down to no avail, had it on a computer at a yamaha dealer that did not show anything wrong, blah blah. I have read that it may be the fuel pump, throttle position sensor, the vapor separater tank ,

It's getting expensive ruling out all of these so I could use a little advice if anyone on the forum has run into similar problems.

Thanks
 
What kind of engine is it (2-stroke, HPDI, 4-stroke)?

Sounds like a fuel restriction but also could be down one cylinder. Have you or the mechanics done a compression test?
 
They made a 4 stroke and 2 stroke in 2002. As mentioned before we need to know which it is to start diagnosing.
 
If it is then he may be into the corrosion problem. First thing I would look into.
 
I have a 2003 225 4 stroke and the only thing I've had like that was the plugs went before a 100 hrs-new plugs and the rpms came back. No problems since-but I see you changed plugs for the correct by the book ones?
 
I have a 225 yami ox66 2 stroke that was having very similar symptoms. I'd throttle up and it would go fine for a few minutes and then bog down. Couldn't get it to throttle over 4200 rpm at times but if throttle babied could get it to run fine. Turned out that 2 of the diaphrams on the 3 fuel pumps had small tears in them. Replaced and engine is running as good as ever. Have best yami mechanic out there. Good guy great service. Pm me and I will send you his #
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it is a 4 stroke. The symtoms for corrosion seem to be overheating while mine on the computer was probably running 10 degrees cooler than it should. I'll do a compression check today but that should have shown up on the computer?? is my guess PM sent to Morganic and thanks to all for the imput
 
Hey could be your throttle position sensor, if it has a dead spot the computer will think it is at idle, you can test it by locating it, it should have 3 wires going into it, basically 5 volts is sent to it and its a variable risistor sending out 0-5 volts to the computer, the voltage sent back to the computer will determine the position of your throttle and the computer then creates the correct fuel to air ratio.

Had this problem on my 115 merc 4 stroke EFI (yami powerhead) and ended up being a faulty TPS. Worht looking into, and easy to fix yourself

PM me if you have any questions


One other thing to look into is if it is EFI you should look into flow testing or cleaning your Injectors, common problem with them clogging up over time, something else to look into, lots of info on the internet regarding this.

good luck,

Cheers
Sudsy
 
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Symptoms don't necessarily sound like corrosion issue---could be fuel pump issue / VST issue. VST can be drained and cleaned. Here's a post I found on another site: Might give you some ideas on where to start looking----

QUOTE

last October my 2004 F-225 lost RMP while leaving the dock. When I advanced power lever to 2100 RPM it would just bog down. Called a mechanic and ran the boat at the dock. Put it under load and it worked fine. Left the dock and got 6000 RPM for almost an hour. Then RPM dropped off and and boat would barely run above idle. 1/2 hour later boat ran fine. When we put it on the trailer it would not get above 1500 RPM.

Mechanic said VST screen was probably clogged so we removed it. it was full of white chalky stuff. Cleaned the VST screen and boat ran great for 14 hours. Same problem returned but have more depth now. When accelerating, sometimes at a RPM range near 2000, or 3000 or 5000 the boat suddenly bogs down. If you continue to push up the throttle RPM decreases but when you pull the throttle back, at some point RPM increases again. When it happens engine does run rougher than normal but one minute later smooth as can be at 6000 rpm. Put a fuel gauge on the rail pressure at 42 lbs then suddenly drops to 20 then boat runs real rough at 10 shuts down. Ran on an external tank same problem. Have done diagnostic several times no problems show up.

Took the VST screen off again and found it full of white powder. Found the bottom of the VST tank corroded. replaced the VST tank. Same problem. Took all fuel (clean) out of the tank. Replaced pick up and fuel tank indicator. Replaced all filters on the engine several times, replaced racor several times. Changed the ball, All has had no effect on the problem. last week decided to change the HP fuel pump. Pump looked good, clean could not get any deposits out of it. Finally ran the boat today and the problem is the same. Seems to be totally starving for fuel (sometimes). Initially would not get above 1500 rpm then 2200, then 3100 then suddenly it accelerated normally and got 5700 RPM and ran smooth. As soon as I pulled it back it would not get above 2000 again for the rest of the trial.

The real symptoms, run the motor in a bag. looks and runs smooth. Put it under load and it seems at some point (low RPM) to start running a little rough. Advance the throttle and everything feels normal until a certain RPM and then RPM decreases rapidly and engine starves for fuel. Bogs sometimes backfires or just sputters. Pull throttle back and at some point RPM increases to a point.

I guess in re-thinking the problem, most probably the severely clogged VST screen was probably never the problem or it was just part of a problem. The only thing left is the fuel regulator and I'm not sure if this would have these symptoms or not. I think having the pressure drop on the rail eliminates injectors, injector pumps and the like. I think. Of course today it ran at almost full power without skipping a beat for several minutes.

I now have been given the idea to pinch the return line when it happens to see if the regulator is porting too much fuel. I'll try that next time I can out the boat in the water.

UNQUOTE

One of the respondents to this suggested also looking at the VST float valve. Have a look at boats.net ---you can find the entire micro-fiche of the VST of your outboard, plus all the part numbers

good luck
 
I had the same issue with a Merc ......... found a faulty wire to a plug to be the problem ......... had me stumped as I thought it was a fuel related issue for sure, just a thought.

Good luck

Ht
 
well I finally fixed it. the screen in the vst was the culprit. funny how easy a fix it was and yet hard to get it diagnosed. thanks to members for the input
 
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