2012 80hp 4 stroke wont rev out

[99yam40]

But I suspect the engine is overheating seizing, limp mode or not. Easy to miss the obvious, have you tried stopping the engine and let it cool for the period that you would have spent cleaning, but don't do anything, then try running it again. What happens?
Go look behind the thermastat housing for build up of of salt and crud. Your thermastat itself maybe faulty. Is your tell tale healthy, when was water pump done? Worth a look there.
Sorry you're getting the usual answers here. There is a faulty human expectation that by doing the same thing over and over again, that somehow we expect a different result.

I believe we have already addressed the gauges and alarm system not showing any problems along with the computer not showing a problem while the reduction of RPM is happening.

So no reason to keep going over all of that unless that was not the truth

[Jordanhack]

Thanks for the replies once again. The mechanic is coming out free of charge next week. At this stage im still thinking contaminating still coming from fuel although not sure how , or could it possibly be a faulty injector that comes good for a little while after being cleaned then starts to play up again? Thoughts?

[TownsendsFJR1300]

Please clarify.

When the injectors and VST were cleaned, WAS THERE DIRT / CRAP FOUND???


Do you have a built in fuel tank or portable tank?


If there was crap in those filters previously, obviously they need to be cleaned again and then run the engine on a PORTABLE tank (that is CLEAN) and known CLEAN FUEL in it.
Flushing the system when / if cleaning filters should also be done..

I would also inspect the inside of your fuel lines as ethanol can (and will) break down the internal liner turning it to mush (it happened to me) causing issues

[DennisG01]

Maybe try running with the fuel cap removed. If there's a clog in the hull vent or the vent line has a dip in it (accumulating liquid), that could cause a fuel starvation issue after a set period of time. Letting the engine set for a while (off) would allow the vacuum that was created in the tank to dissipate. Running with the fuel cap removed is a quick/easy check for a vent clog. Or... next time it starts bogging down, then remove the fuel cap - if it gets better in short time, you found the problem. If it doesn't get better (and after double checking by pumping the bulb a bit), then the issue is elsewhere.

[Jordanhack]

Yes there was crap found in the vst and injectors . We have run completely new and clean portable fuel tank lines and filter since this first happened. Certainly not a breather issue as once the poor running starts it does not go away until we have cleaned the injection system

[walleye1]

Take a fuel sample to see if you have water in the fuel.

[99yam40]

If contamination is the problem,
you need to find out what is getting plugged up
and then where is the stuff that is plugging things up coming from.

Does just cleaning the injectors help, or does just cleaning the VST help?
doing it all at once does not tell you what helps to solve the problem

You have not addressed my question

[DennisG01]

When the issue happens, drain some fuel out of the VST tank into a clear, glass jar (spaghetti jar works well). And, as mentioned, a fuel pressure gauge can do wonders to help figure things out.

[pstephens46]

You have not addressed my question

The problem is the OP is posting for the owner.
He may not have the specifics. Without, we are pishing into the wind.

[panasonic]

I believe that they are running this engine off a portable tank...no build in tank on the boat. Hopefully the OP will confirm this.

[Jordanhack]

Yes the engine is being run off a brand new portable tank and there appears to be no crud water etc coming through the fuel when emptied into a clear jar.

99yam40 after the first time it happened the mechanic only did the injectors + we changed all filters, tanks, fresh fuel and lines. Boat ran fine for half hour then wouldn't go passed 2600rpm and was rough. After the second time it happened a different mechanic did the injectors, replaced high pressure fuel pump (although i think it was working fine) and sand blasted VST tank. An hour or so running and motor did same thing- 2600rpm and no more. Still running like crap a week after boat was last out

[99yam40]

bad stuff hiding in lift fuel pump and maybe lines on motor?

flow testing the injectors may help ID what injector has a problem or if more than on has a problem.

doing multiple things at once makes it hard to figure out which helped

[DennisG01]

You've mentioned a 'limp mode' a few times... which makes sense, except... you also mentioned that when the issue is happening you had a diagnostic tool hooked up and nothing was wrong. I would think that eliminates the limp mode scenario. Unless the tool you are using is faulty or cannot read Yamaha codes?

After the issue happens... have you ever just let the engine sit for a day and then tried to see if the issue went away by itself? I'm wondering if there is some kind of heat soak thing happening and 'cleaning the injectors, etc' fixed things, but really it was the time needed for the engine to cool down. Just tossing the idea out there.

To me, it still feels like a fuel issue, though.

[99yam40]

from he wrote it does not go away by itself
"Still running like crap a week after boat was last out"

[DennisG01]

from he wrote it does not go away by itself
"Still running like crap a week after boat was last out"

Thanks - missed that part.