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Difficult restarts when warm

loose_cannonloose_cannon Posts: 592 Officer
edited June 2022 in Boating #1
1998 Johnson 175 (J175EXECD) is hard to keep running after a hot soak. A typical scenario is a 22-mile run offshore, dropping anchor and then a restart after 30-minutes. The engine will fire immediately, but stalls instantly when put into gear.
It takes repeated restarts, generous fast idle on the throttle and even a quick hit of the primer to get it running good enough to put into gear. Once I get it to throttle up while in gear, it runs perfectly. Sometimes this can take up to five-minutes, which is not good when you are trying to pick up divers or get away from a dock

I know these engines are known for this hot soak issue, but is there any other contributing factor(s) like a stuck vapor separator float or timing issue that might cause it?
Any quick checks to verify these systems are working?
Join Date: March 2001
Member #813


  • BillgranBillgran Posts: 350 Deckhand
    ethanol fuel makes it worse.

    Try popping the front latch an lift the motor cover up a bit after shutting down. That allows a flow of cooler air through the motor cover area to help cool the motor before boiling out the fuel.

    I've been meaning to try the 1" dia. caged-ball valves mounted in each motor pan to see if that helps. They are used on the FICHT and E-TEC engines to help air flow when the motor is stopped.

    "There is never just one thing wrong with a boat"
    --- Travis McGee

  • loose_cannonloose_cannon Posts: 592 Officer
    I might be willing to guinea pig that idea...
    Join Date: March 2001
    Member #813
  • BillgranBillgran Posts: 350 Deckhand
    # 5004576 - valve assembly - quantity 2 - about $9 apiece

    Remove side covers and drill a 1" hole on the horizontal area for the valves to snap into. Measure carefully as there is not a lot of room underneath the shelf area.

    "There is never just one thing wrong with a boat"
    --- Travis McGee

  • Circle-HookCircle-Hook Posts: 503 Officer
    1998 150 hp,60^ same story. Long run, sit 30 minutes - no want to start.
    There is a bunch a crap just in front of fuel pump- the vapor seperator system- this thing has it's own vapor pump, a fuel bowl and needle seat just like a carb and a lot of iffy connection. Since all of this is under suction from the fuel pump which is "behind" all this stuff. I think these engines heat up and get a air leak that breaks the vaccum of the pump.
    My fix was a was to strip all of this stuff off including the fuel pump because it was leaking. (Note: a new fuel pump had been installed and did not help)
    I installed an electric marine, coast guard approved pump according to manufature's instructions. It worked.

    The less nuclear solution suggested by electric pump people is to use the electric pump as a booster pump. Leave everything in place and put the booster pump in front of the vapor system. If done according to instructions, this is a perfectly safe thing to do.
    I was already leaking fuel from existing pump so I gutted it.
    Pump is well under a 100 bucks - I paid 45.00.
  • BillgranBillgran Posts: 350 Deckhand
    Do you have some sort of safety circuit so the pump will not run if the key is ON and the motor quits or is not running? You don't want to pump pressurized fuel if you get a leak or the carburetors start to flood.

    "There is never just one thing wrong with a boat"
    --- Travis McGee

  • Circle-HookCircle-Hook Posts: 503 Officer
    No, there is no good way to "sense" the motor has died with the key on. Other than the obvious like of the engine not running. A few minutes of this as when starting will not do any harm, extended run time with fuel flow blocked (carbs full) is not recommended by pump manufacture. I have an additional cutoff switch located on the dash. In my case the voltage pulse caused by the pump make the voltage meter wiggle, giving me a sign that the pump is running if I forget.
    I am thinking of adding a dash light also.
    As for leaking or flooding carbs, if you got a leak - you got a leak- no matter what pump you use and properly set carbs are going to block incomming fuel once full and needle seats.

    If you have an idea how to block voltage to pump when key on and motor not running I would be pleased to hear it. If you don't need it - do not use. For those who have fought this issue, it is a solution. It is not perfect, just better.
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