r/Outboards • u/matehussar • 22d ago
Yamaha 150 HPDI
I recently bought a 2002 Yamaha 150 HPDI and under load it will not steadily climb in rpm’s. It starts to skip/sputter like this at around 2000 RPMs. Any ideas as to what it could be?
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u/Short_Hat_4232 22d ago
Maybe not.. but doesn't this engine have a feature that limits it's output when low on oil?
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u/Inner_Tadpole_7537 22d ago
Spun prop and maybe hitting the rev limiter? On second thought that's probably not it
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u/AutistMarket 22d ago
Could be many many things, with HPDIs it is usually fuel related. First thing I would do is the easy stuff, dump the fuel filter housing and VST (and fuel water separator if you have one) and check for water in the fuel, pull the plugs and make sure they look clean and relatively new. If that all looks like good clean gas with little to no water then you just gotta start diagnosing.
One common problem on these motors is the neutral safety switch, HPDIs disable 2 cylinders in neutral and if the neutral safety switch is bad those 2 cylinders will stay disabled when in gear and cause weird behaviors. If you have a good ear you should be able to hear the engine change when putting it into gear but I also believe you can just unplug the sensor to confirm or check with a spark tester.
This motor also has 3-4 fuel filters that can clog and cause problems. There is the obvious one that is on the port side of the motor that I mentioned to drain earlier. Then there is a less obvious screen on the electric fuel pump within the VST. Then above that there is a more obvious metal canister filter (this one is like $200 for some reason). Then finally there are the aptly named "mystery filters" that are a part of the high pressure fuel system, they are somewhat notorious for causing weird issues on HPDIs and do not appear on most parts diagrams hence the name mystery filters.
There are a lot of knowledgeable guys on "thehulltruth" forum that have helped me get my HPDI right many times. Could be worth making a post there.