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1995 90hp overheat

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  • 1995 90hp overheat

    Boat the boat used, PO said he had issues with the overheat alarm every now and then and mentioned the rubber water divertors in the heads. So we changed those, water pump kit, thermostats. Still got the alarm when going WOT. My dad was driving and didn’t shut it off when he got the alarm
    and it blew the motor. The rings were broken on one cylinder so he had it rebuilt. Still constantly getting the alarm, only does it when going above 4K rpm and trimming up. After maybe 3 mins it’ll alarm and then I’ll idle down and in 45 secs the alarm goes clears. I started thinking the motor may be set to high from research online and cavating when trimmed up. We lowered the motor, replaced the pump kit (old one still looked good) and I pulled the heads and noticed the rubber divertors were almost completely blocking the water flow so I changed them as well with new head gaskets. I’m only getting 7psi for water pressure then 10psi at wot around 5k rpm. It ran great today, didn’t alarm as much but still had one alarm on the way back to launch when driving 5k rpm. I had my infrared gun and both sides were running 150-160ish at that point, once idling down and getting the cowl off.

    Question is what can cause my low water pressure. We stick a rod up the water intake tub and didn’t feel anything obvious. I’m getting so fed up I don’t know what else to check on it. Something has to be blocked.... but where?

  • #2
    Post a model number. They made two different 90hp that year.
    '47 18' CC Utility "Knock On Wood"
    Various Evinrude powered Pontoons all named "Floosy"

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    • #3
      With diverters I would gave to say it is a " crossflow " model.-----Have you looked at or changed thermostats and poppit valves on this motor ?

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      • #4
        Thermostats and poppit valves were changed before the rebuild but that’s on the list today to inspect again. It was running 15-17psi then got into some shallow stuff with mud and hasn’t been passed 10 since.

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        • #5
          Thermostats are off and I texted them on the stove they are opening up around 120. Everything looked good to me. Going to flush water directly into the thermostat manifold and see if any thing is plugged. Should I drop the lower unit and flush up the intake tube as well?

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          • #6
            The port side of the thermostat manifold seems like there is metal hole missing after the thermostat. I’ll try to attach the picture. It doesn’t look like a clean cut hole. Almost looks like something broke. Where does the water flow go after this? The exhaust manifold ? Wonder if something is plugged in there causing my low pressure.

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            • #7
              This is the port side. The other side looks normal too me

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              • #8
                You can backflush through the hose connections at the bottom of each cylinder head, best done with the leg off. Flushing through the thermostat mounting plate should just pump water into the exhaust housing (leg).
                '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
                Avatar: "Ship Arriving Too Late to Save a Drowning Witch" - Zappa
                My 90-140 engine up-build thread: http://tinyurl.com/hz8uv47


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                • #9
                  Ok I back flushed from where the thermostat hose attaches into the cylinders. Hit both sides a few times and also down where the thermostats go and put the exhaust. One of my thermostats was slightly open, when I shook it you can sorta hear it rattle. When I say open I mean very slightly but maybe that was enough to keep my water pressure on he low side. After I flushed backwards I found a small peice some green sponge stuff that came out. Hooked it up to the muffs and was showing 4psi before today I was showing 0-1psi while on the muffs some something helped and I will put the boat in the water tomorrow and post how it goes.

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                  • #10
                    Sounds like you're on to something. Hope it works better now.
                    '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
                    Avatar: "Ship Arriving Too Late to Save a Drowning Witch" - Zappa
                    My 90-140 engine up-build thread: http://tinyurl.com/hz8uv47


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                    • #11
                      Took it out yesterday for a quick run just to see what kind of water pressure I had and at 5k rpm I had 12-13. Still seems kind of low to me, is it? Or is it enough?

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                      • #12
                        Better. Mine is north of 25 at WOT. Have you purged the line to the pressure gauge? You did say you got it in the mud.
                        '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
                        Avatar: "Ship Arriving Too Late to Save a Drowning Witch" - Zappa
                        My 90-140 engine up-build thread: http://tinyurl.com/hz8uv47


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                        • #13
                          Yes I blew the hose to the pressure gauge with my air compressor. Line had a very small amount of water but that was it.

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                          • #14
                            What brand pump kit did you get? I use BRP. Not sure if others give different pressure.
                            '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
                            Avatar: "Ship Arriving Too Late to Save a Drowning Witch" - Zappa
                            My 90-140 engine up-build thread: http://tinyurl.com/hz8uv47


                            Comment


                            • #15
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                              Took it out again today and staying around 11 psi. Gave me the over heat alarm twice today so I ran it easy. Anyone suggest trying to descale it with either vinegar or murtaic acid?

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