2004 Yamaha 150 outboard

[bieke1@msn.com]

Been checking everything, fuel pressure, coils, injectors,plugs , wires , all will be new . Suspecting that the ecm . is bad
Runs very sluggish, backfires at times , , won't go over 25 mph , normally 55mph .
can the ecm be replaced without programming , or will it need to be programmed
any thoughts?

[DennisG01]

Been checking everything, fuel pressure, coils, injectors,plugs , wires , all will be new . Suspecting that the ecm . is bad
Runs very sluggish, backfires at times , , won't go over 25 mph , normally 55mph .
can the ecm be replaced without programming , or will it need to be programmed
any thoughts?

You said all WILL be new, which means you haven't replaced those things and ran the boat again. Probably be best to wait and see. But, did you measure pressure under load? Check fuel quality? Change fuel/water separator and dump the fuel into a clear container and observe? Drain the VST and check fuel for quality? How about the on-engine filter... is the red ring floating?

[bieke1@msn.com]

Originally i found what looked like sawdust in fuel separator, i cleaned it out , also i was having some issues with the prime ball not pumping up , i replaced prime ball , cut it open and found it full of gunk ,
I pumped out the fuel tank through a clear filter and never had any more crud in filter,then added new fuel , installed new spark plugs , and fuel filter .
Ran the boat and still not tunning well , fuel pressure is at 40 or more under load and maintains pressure, plug wires ohm out as open for some reason, i have a set of wires ordered, coils and injectors, they were not that expensive and it as a 2004 motor so as soon as the new parts are here i will find out if that could be it . Also i have removed the fuel pump housing and checked for gunk in it , It was clean,
When i accelerate it at times will backfire, most of the time it just Boggs down and the boat won't go over 25 mph .
The injectors ohm out ok but i will replace then anyway, i figure i will just have spare parts.
I was just wondering if this does not fix the problem, and if i did end up replacing the ECM if it was a part that could just be switched out , or if programming would be required .

[ausnoelm]

I think you're a long way off replacing the ECU, it can be simply replaced, but, you need to do the basics first, you hard dirty fuel, chances are you still have crap somewhere, run it off a remote tank complete with fresh fuel and fuel line, then start cleaning from the fuel connection forward. Do you have good spark on all cylinders?

[99yam40]

if the rail pressure stays in spec while the motor bogs down, I would be looking at the injectors.
.
may need to send them off for flow testing and cleaning

[pstephens46]

Filthy fuel. Clean that up first. Don’t waste time on coils, ecu, etc. that motor must have sat up for a long time to create those issues.

[DennisG01]

Kind of already been said, but I certainly wouldn't be doing anything with the ECM without diagnosing what's going on - the last thing you want to do is just keep throwing parts at it. For example, injectors can be cleaned/rebuilt for about $20 each. You may want to try one more thing, as noted above, with the fuel - just to eliminate most of the fuel system as a potential problem and hook-up a portable tank to the VST tank unless as mentioned above, the pressure STAYS constant when the issue happens... it wasn't clear from what you wrote. You could also observe the on-engine filter and the fuel level in it while running the boat.

What do the plugs look like?

There's no way all the plug wires ohm out as open, like you said - otherwise the engine wouldn't even start. My guess is that just didn't test them properly or there's an issue with your meter.

[TownsendsFJR1300]

Is this a 2 or 4 stroke engine?? Model maybe?

[99yam40]

also, that saw dust looking stuff in the filter may be fuel lines falling apart inside
may need to replace some lines.

injector cleaning hopefully helps