Yamaha 225 SHO holeshot / low end issue

[Captain Jiffy]

I have a 2005 Triton Tr-20X with a 2014 225 Yamaha SHO. I am having an issue with holeshot. I have a 10" Atlas hydraulic and two 10ft talons. I used to have whip cracking hole shot now I have to run my plate all the way up and it barely comes out of the hole with 2 people and full livewells, its even worse when I am full of fuel. The engine will rev up quickly to 3000-3100 RPM and then stall out at that RPM, then after a few seconds it will finally continue to rev up (quickly) and come out of the hole good. Sometimes I have to try 2-3 times to get the boat up on plane. If I run my jackplate all the way down or anything under 1/2 up the boat will not plane out at all. I just had the boat at the dealer last summer and they changed the low pressure fuel pump under warranty I didn't get to rum it too much after this but it's still doing the same thing. Top end is fine 72+. It seems to be getting worse as the weather warms up. I took it to the lake back in January and it will pull excellent holeshot accelerating nicely from 800RPM to up on plane, no evidence of any hesitation. It was about 40F that day. I am now out of warranty and the dealer wants to change the high pressure fuel pump. I have Lowrance units that allow me to monitor most engine functions and I keep a close eye on fuel pressure and oil pressure. When the issue occurs, I do not see a drop in the fuel pressure, it holds around 15PSI. Is there some sensor that needs changing. Help is appreciated!

[fairdeal]

I have Lowrance units that allow me to monitor most engine functions and I keep a close eye on fuel pressure and oil pressure. When the issue occurs, I do not see a drop in the fuel pressure, it holds around 15PSI

I don't think you are seeing 'fuel pressure'
if you were, you would see ~45 psi, not 15.

(but certainly would be very helpful to know the rail pressure at that time)



I don't see the high pressure pump as a likely culprit,
disturbs me that your dealer wants to change it...

but IMO it would be a good idea to open up the VST and get a look at the screen inside

[99yam40]

could it be water pressure he is reading 15psi on?
but then I had no idea they showed Oil pressure either

[fairdeal]

my guess: MAP

[Captain Jiffy]

Thanks for the replies guys. Here is a snip showing what data is being displayed on my Lowrance graph via the engine interface cable. It definitely isn't water pressure, I have that on a manual gauge.

[DennisG01]

That pic doesn't show the "15PSI" and what it is measuring, though. Two things could be happening here... either you are confused as to what that 15PSI is or you have found your problem (or at least the first thing to address). Can you clarify? Might be best to run with a manual fuel pressure gauge on the engine.

How's your fuel quality? Drain the VST and check. How's the VST filter? Pull it and check it out.

What does the primer bulb feel like during the issue? Try running with the fuel cap off. Or, better yet, plumb a portable tank direct to the engine - that's an excellent first step to narrow down a whole bunch of possibilities.

[Captain Jiffy]

I will post some pictures later tonight of the screen on my Lowrance units showing the gauges. I know it has a header for what that is monitoring but I cannot remember. It may say something like "boost pressure" but I am not sure. I was reading up on the VST filter and it seems to cause more problems at WOT than during holeshot I will call the dealership and ask if they changed it last year while they replaced the low pressure fuel pump under warranty. As my original post, I have no issues with power once I am on plane and top end runs perfect with no hestitation or glitches.

[DennisG01]

I will post some pictures later tonight of the screen on my Lowrance units showing the gauges. I know it has a header for what that is monitoring but I cannot remember. It may say something like "boost pressure" but I am not sure. I was reading up on the VST filter and it seems to cause more problems at WOT than during holeshot I will call the dealership and ask if they changed it last year while they replaced the low pressure fuel pump under warranty. As my original post, I have no issues with power once I am on plane and top end runs perfect with no hestitation or glitches.

"Boost pressure" That engine doesn't have a turbo/supercharger, does it? I didn't think it did.

Start with the items mentioned - check those things out. Replacing the VST filter last year doesn't mean anything at this point. The items that have been mentioned are all good starting points. If this is out of your comfort level, which is fine of course, you might be best served to take it to a shop. If you're not able to wrench on it, we really won't be of much help... seeing as how we can't do it for you! Not that we could, right now, anyways!!!

Why does the dealer want to change the HP pump? Did they diagnose it in person?

[fairdeal]

The NMEA 2000 standards cover a broad range of application
its up to the individual manufacturer to decide how to use them

for some reason - inscrutable, to me -
Yamaha (or Mitsubishi -who actually makes the ECM)
decided to have the ECM report the MAP value -
Manifold Absolute Pressure
(what, in the old days, we called 'manifold vacuum)
via NMEA 2000, using the "Boost Pressure" parameter.

AFAIK, Yamaha's own Command Link gauges/displays
do not use / show that parameter.

It is only visible when using a '3rd party' chartplotter

[Captain Jiffy]

I confirmed last night that the gauge shown on the Lowrance unit does state "BOOST" so that would map over to the MAP value. I am fairly handy and have rebuilt a couple of engines over my years so I don't have any issue replacing the VST filter myself. Are there any other filters I should replace while I am in there? I cannot find any videos on YouTube showing how to replace the VST on a SHO engine but I did find one for a saltwater Yamaha that looks to be almost identical, https://www.youtube.com/watch?v=unCa4aZy3BI. Can someone confirm? Also, I had asked before if a clogged VST can cause low end issues? Most information I found on VST is high end issues.

[fairdeal]

I did find one for a saltwater Yamaha that looks to be almost identical, https://www.youtube.com/watch?v=unCa4aZy3BI. Can someone confirm?

Yes, the VST is identical.
Seems a very helpful video -
particularly the advice/example of taking sequential photos at every disassembly step.

He shows the two filters,
the first 'in the bottom' is usually what causes loss of top end/high load power,
as its a restriction on the intake of the pump.

The volume of fuel needed at idle/low rpm/load is much less,
so the restriction is not usually an issue then.

[Captain Jiffy]

Thank you, my boat certainly seems to "bog down" under high load (which is during holeshot), it is the worst when I am full of fuel, 2 people, full livewells and wet carpet (from rain). I will order the two filters and change them and post results after this. It is interesting that as the water gets warmer, and the air temperature gets warmer, that the issue is getting worse.

[TownsendsFJR1300]

If that filters clogged/ semi clogged, it'll get worse the more the engines run...

It could be getting colder, less passengers, the filter is simply (likely), simply clogging up the more you run it...

.

[Captain Jiffy]

If that filters clogged/ semi clogged, it'll get worse the more the engines run...

It could be getting colder, less passengers, the filter is simply (likely), simply clogging up the more you run it...

.

Update from the past few days.
I have observed that on the first run of the day that the engine does really well out of the hole, then as the day goes on the issue gets worse.This could match very well to the issue you describe above.
Filters are on order, should get them within a week. I will post results after changing them.

[99yam40]

I would think that the rail pressure would be dropping if the screens/filter were a problem. that should be easy enough to monitor when the problem shows up.

sounds like the motor is not producing enough HP to turn the prop when the motor is loaded heavy.
injectors or restricted fuel flow would not get better.
maybe timing is being changed.
does this motor have O2 sensor or knock sensor?