[coastwise]

I have a 2000 yamaha 250 saltwater series 2 engine. It has been a great engine but recently have had a bogging down issue. Here are the symptoms
1. the first 10 minutes I run the engine at any speed and it is fine.
2. After that at any rpm above 1500 the engine will drop down in speed surge up then drop down and continue "bogging down".
3. It always starts fine and runs at a good planing speed 4800-5000 rpms for around 10 minutes then starts to bog down or surge .
4. The gas is fine. My racor does not have any water in it. The gas tanks are new I replaced them last year. The vents are clear.
5. it seems like it is a fuel issue like it cant get enough fuel at higher rpms.
6. One other thing when the boat hits waves it seems to trigger the hesitation. I
7.. I think the engine has a canister filter are there other filters I should know about. Has any one encountered this before. Any advise. Thanks

[Les MacDougall]

There's a fine screen the the High pressure Fuel pump houseing.
Mine was clogged, I'll bet yours is too.
However, that only fixed it the first time,when it wouldn't get off plane.
I have the exact same engine , with the exact same symptoms (including the hitting wave)and can't run long distances over 3500rpms, The Harder it runs , the quicker it stalls.

It has 35psi of fuel pressure and 4in Hg of vacuum, which according some other advice is correct.

I'm thinking about , replacing the screen, even though it looks clean!

The Pumps is new.
The 3 fuel pumps are new.
The fuel filter is new.

Keep in touch.

Les

[rodbolt]

check fuel rail pressure and fuel system vacum at the problem RPM or WOT. testing at idle with no load is fairly useless,kinda like a teat on a boar hog.
if fuel rail pressure and fuel system vacum remain within spec then use the diagnostic test lamp to check for any codes generated,
always remember that ECU WILL NOT store codes and will only display them when they are active so all tests have to be done at the problem RPM AND LOAD. revving it on the flusher usually isnt enough.
last week I actually got one that the VST had been resealed with silicone sealant.
not only had the excess silly cone clogged the VST but it also took out that silly 360 dollar O2 sensor that doesnt like silly cone.
this engine is not difficult to diagnose but it does require a working knowledge of speed/density EFI systems and a certian amount of test equipment or a large cash outlay on parts swapping up to and including burning a piston.

[Les MacDougall]

Here's the link to the parts veiw of that filter screen.

http://www.yamaha-motor.com/outboard/parts/home.aspx


I'm going to another fuel pressure gauge, to test with, when the stores open tommorrow.
Les