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  1. #1
    Member
    Join Date
    Aug 2016
    Location
    New Hampshire
    Posts
    5

    2001 150 EFI RPM issues

    Serial # OT266447. I'll start off by saying that I have not used my boat in the last couple of years and found out I needed a new VST last year. Brought it to the shop recently, after I found a VST online, and had them install. Also had my injectors serviced and new plugs put in while it was there. Engine ran great at the shop on their fuel cell. Took it out for the first time and the engine started with no issues, sounded great and after 5 minutes running at idle speed through the channel, I got the boat up on plane and was running between 4-4500 RPM's for about 2-3 minutes when the RPM's started to drop finally settling in at a max of 2100 RPM's. Tried to take it out of gear but boat would idle ~1500 RPM. Had to shut it off in order to get it back into neutral. Waited a few minutes and tried starting it up and it would rev right up to 3500 RPM's, did this a couple times so I did not run it again. I brought it back to the shop and they suspect that it may be the fuel. When I drained the tank I may not have gotten all of the suspect fuel out of it before I added 20 gallons but it was not like the engine ever coughed or anything it just slowly lost RPM's. Any ideas??

    I also noticed that my water stream from the engine happened instantly, used to take a while to flow (believe thermostat needs to reach certain temp). Is this possibly a bad thermostat or not connected wire. How would I check?

  2. Member
    Join Date
    Mar 2012
    Location
    Pelham, GA
    Posts
    2,004
    #2
    Pull your thermostats and check them, something could be sticking them open or they could have failed. Could it cause your problem? Not sure but it is important for your motor to reach a certain temp and fuel delivery is influenced by temp readings, I think.

    The over revving seems like a fuel problem or throttle sensor problem. Run motor with cowl off and make sure there are no fuel leaks on the motor. Fuel spraying under the cowl will be sucked in to the intake and cause it to rev. A leaking or flooded my VST could do the same if it's not functioning properly.