East Coast Dave Posted July 1, 2016 Report Share Posted July 1, 2016 Just had the boats serviced. I was running it and it start to shut down at 4300 rpms. Then it would run wot for couple minute and they cut out again. I'm thinking may water in the gas. Then I noticed the bulb was firm / hard. Thinking that may be part of the issue. Thoughts? Link to comment Share on other sites More sharing options...
firstdue Posted July 1, 2016 Report Share Posted July 1, 2016 Dave, May want to put new VST filters on your motor. My 250 was doing a similar thing but between 4850-5400rpms, my local dealership was no help kept saying water in fuel. I googled it and swapped them out in about 45 minutes instantly corrected the problem. My 2 filters for the high pressure and low pressure side of the injection system were about $100 bucks and they look like something you would find on a lawn mower!! I believe the 150 has them on the rear of the motor under some parts they are not easily accessible . Jm Link to comment Share on other sites More sharing options...
Bamaskeet Posted July 1, 2016 Report Share Posted July 1, 2016 I suggest you check your water separating gas filter. It should tell you if you have a fuel issue. Link to comment Share on other sites More sharing options...
jason p Posted July 1, 2016 Report Share Posted July 1, 2016 Sounds like a VST filter issue to me as well. I'd get a filter cutter and check the separator first (it's easier and you'll have fun cutting fuel, oil, etc... Filters apart every time you change them from now on) The VST filter bowl, which is just a pressurized float bowl for EFI will corrode eventually from water settling to the bottom, especially if the boats sits for any length of time. It's not too difficult to check just time consuming since you need to remove the intake manifold to get to it. Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 2, 2016 Author Report Share Posted July 2, 2016 I guess it's time to pull off the lift and see if I can do this..... Will I need any other gaskets or anything when doing this? Link to comment Share on other sites More sharing options...
firstdue Posted July 2, 2016 Report Share Posted July 2, 2016 I did not need anything other than a 10mm socket with a swivel extension and a long Phillips head screw driver. No gaskets needed on mine just the 2 filters. There are some great videos on you tube also with tips to make it fairly Ez. I never had a water in fuel issue , I cut my filters and drained them nothing found. It was crazy how restricted the VST filters were compared with the new ones. 300 HR service item per the manual also. jim Link to comment Share on other sites More sharing options...
jason p Posted July 2, 2016 Report Share Posted July 2, 2016 1 hour ago, East Coast Dave said: I guess it's time to pull off the lift and see if I can do this..... Will I need any other gaskets or anything when doing this? I would get an intake manifold gasket: if you mess up the old one, re-install it and lean the motor out the VST will be the least of your worries. There is an o-ring between the top and bottom of the VST, and definately get the grommet that holds the high pressure fuel pump up in the top of the VST. The grommet may be swollen and brittle from ethanol. You don't have to pull the high pressure pump out of the top of the VST but you may see little pieces of the grommet in the bottom of the tank, I did in mine anyway, I suspect from the ethanol pulling the moisture from the rubber causing brittleness. If you don't use the grommet you can return it (it's a $20-something piece of rubber) Look in the bottom of the tank, you may see corrosion in the form of the anodizing coming off the aluminum inside the tank. If you do, look in the filter screen it will probably be in there too, it's a super fine stainless mesh filter. You may want to consider a new VST "bowl" if this is the case, it's not going to get any better. Link to comment Share on other sites More sharing options...
Lap it Up Posted July 2, 2016 Report Share Posted July 2, 2016 Do you run a lot of E-gas? Bad/swollen injector o-rings can also cause your condition. I've changed quite a few on four strokes. Getting the injectors cleaned and flow tested is a good idea also. Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 2, 2016 Author Report Share Posted July 2, 2016 I've never used ethanol gas in the boat for the past two years or so that I've owned the boat. I just had the service done to the boat last week so I'm thinking it's not the water fuel separator. I just replace the fuel bulb on it yesterday to eliminate that. Never had the problem before.... I'm hoping it's the VST filters. If it were water in the gas wouldn't it do it at lowers speeds? Link to comment Share on other sites More sharing options...
jason p Posted July 3, 2016 Report Share Posted July 3, 2016 Something else you can check before digging into the VST: when the motor starts to bog have you tried to pump the primer bulb? If this remedies the issue the low pressure pump (the pump on the valve cover) is bad it won't keep the VST full and will eventually starve the motor at higher RPM. The high pressure pump in the VST has enough suction to pull gas and feed the motor at lower RPM but not at sustained higher RPM. Then when you slow down it catches back up and fills the VST and you're able to run at WOT until the gas in the VST is depleted again. Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 3, 2016 Author Report Share Posted July 3, 2016 5 minutes ago, jason p said: Something else you can check before digging into the VST: when the motor starts to bog have you tried to pump the primer bulb? If this remedies the issue the low pressure pump (the pump on the valve cover) is bad it won't keep the VST full and will eventually starve the motor at higher RPM. The high pressure pump in the VST has enough suction to pull gas and feed the motor at lower RPM but not at sustained higher RPM. Then when you slow down it catches back up and fills the VST and you're able to run at WOT until the gas in the VST is depleted again. I think I'll try that tomorrow. The guy that works on the boat for me said he would have to check the fuel pressure so maybe I can figure it out before. I was really wanting to use the boat this weekend. Thanks for the help Link to comment Share on other sites More sharing options...
jason p Posted July 3, 2016 Report Share Posted July 3, 2016 No sweat and good luck. I've never known anyone to do it, but Yamaha does recommend changing the low pressure pump at 500 hrs. On my F115 anyway. I may be wrong but I'm assuming the F150's are the same. Link to comment Share on other sites More sharing options...
Headhunter Posted July 3, 2016 Report Share Posted July 3, 2016 Dave, I think I have a filter on my workbench Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 5, 2016 Author Report Share Posted July 5, 2016 On July 3, 2016 at 9:09 AM, Headhunter said: Dave, I think I have a filter on my workbench Thanks.. My buddy is going to get me on his schedule to go through it for me this week. I figured I'm pretty mechanical and handy, but I think I'm going to "let the plumber, plumb" if you know what I mean. Thank you for the offer. Hope you had a nice 4th. Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 10, 2016 Author Report Share Posted July 10, 2016 Buddy said it was the pump but I asked him to replace the filters too. Link to comment Share on other sites More sharing options...
jason p Posted July 11, 2016 Report Share Posted July 11, 2016 Low pressure pump? Curious for my own knowledge. Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 11, 2016 Author Report Share Posted July 11, 2016 I'll clarify with him and let you know. My 90 2 stroke did the same thing yesterday on the Maverick.... What the heck? They say it comes in threes so I'm curious what breaks today... Link to comment Share on other sites More sharing options...
mulligan Posted July 11, 2016 Report Share Posted July 11, 2016 Never had a 4 Stoke but curious if the fuel delivery is the same as a 2stroke? Low pressure pump(s) feed the VST where the other fuel pumps take over to feed the motor. Link to comment Share on other sites More sharing options...
jason p Posted July 11, 2016 Report Share Posted July 11, 2016 That's exactly how it works. One low pressure pump runs off a camshaft to keep the VST full and then there's an electric high pressure pump inside the VST that supplies the injectors. Link to comment Share on other sites More sharing options...
bilge rat Posted July 11, 2016 Report Share Posted July 11, 2016 Replace the fuel line from water seperator/primer bulb to motor if it is over a few years old. Under vaccuum the inner liner collapses reducing fuel flow. It can cause the issue you are having. Link to comment Share on other sites More sharing options...
East Coast Dave Posted July 21, 2016 Author Report Share Posted July 21, 2016 High pressure pump. ... Link to comment Share on other sites More sharing options...
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