Engine went in for an annual service and came out running worse. Probably a coincidence, but just want to give all of the facts.
2007 Yamaha 150 4-stroke
Normally max RPM is 5300.
Last Wednesday went offshore. In the river, couldn’t get my RPMs over 4700 (normally I cruise at 4900). By the time we got a few miles past the Jettis, RPM started jumping up and down 2800-3600. Wild fluctuations. Looking at the digital gauge, RPM number is constantly moving up and down (never steady). I normally cruise at around 27-29knts but we were making about 16-19 knts. Port engine was really pulling the bad starboard engine along.
We finished the day offshore with not really any improvement. Even at idle engine was bouncing up and down (shaking\sputtering kind of).
So, a CF.com buddy suggested that we try his fuel injectors on my engine. Popped his injectors in and boat went back up to max RPM (actually even higher than I had ever seen). We ran down the river and back. Things were awesome. He offered that I borrow his injectors for my next offshore trip (yesterday).
Boat ran fantastic until about an hour offshore and then RPMs started to taper off again. Got into that range (bouncing back and forth). We made it offshore about 17 knts. Boat seemed better at trolling and idle speeds though.
After trolling for a few hours we decided to head back in. RPMs came up nicely and we were making good speed (25knts). Then after about an hour of “good”, we lost the power again. Dropped me down to 16 knts again. Was like that all the way home. Hit the city marina no wake zone and idled through. Once we got past the Bristol, I fired up the engines and we were back up to 5300 RPMs all the way to the marina.
Not sure what is going on. He suggests the fuel\water separator change and VST filter change which we will do ASAP. Anyone else have similar issues?
Sounds like you could be sucking air into that engine’s fuel supply. Make sure all of the hoses and fittings leading up to it are tight and in good shape.
I take it this is only on one engine. The VST pump may be failing/shorting causing the intermittent running. Chris V would know better.
Did they give you a rundown on things done ie. valve adjustment/timing belt etc...a lot of things to check...take it back to them and get to work on that fence.
if you have the ability to, swap the fuel lines on the motors…that will eliminate any possibility of loose fuel lines sucking air or anti siphon valves sticking or bad water separator
If I’m posting, its because I’m sitting here at work, dreaming about fishing.
if you have the ability to, swap the fuel lines on the motors…that will eliminate any possibility of loose fuel lines sucking air or anti siphon valves sticking or bad water separator
If I’m posting, its because I’m sitting here at work, dreaming about fishing.
That's interesting. I will have to look at that. I'm not sure if the hoses are long enough, but they might be.
bulbs have a “one way valve” in them, so just because you can get the bulb hard, doesnt mean there might not be a suction issue some where “pre-bulb”
If I’m posting, its because I’m sitting here at work, dreaming about fishing.
Understood, but my assumption is that once the bulb IS hard, then if it was a suction issue upstream I have at least eliminated that for a few seconds and the engine would run "normally" until the bulb went limp again. Wouldn't that be the case?
The fuel bulb only primes the fuel pump. Once the engine starts the fuel pump sucks the fuel through the bulb and pumps it to the vst tank that pressurizes the fuel to the fuel rails/injectors.
" So, a CF.com buddy suggested that we try his fuel injectors on my engine. Popped his injectors in and boat went back up to max RPM (actually even higher than I had ever seen). We ran down the river and back. Things were awesome. He offered that I borrow his injectors for my next offshore trip (yesterday).
Boat ran fantastic until about an hour offshore and then RPMs started to taper off again."
I would imagine you gunked up the traded out injectors again…check the vst tank drain for stool.