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1995 7.4L Thermostat

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  • 1995 7.4L Thermostat

    I finally put the boat in the water and ran the engine for more than a few minutes and found that the temperature never goes above 140 degrees. Now, I never really was above idle but even after idling for 10 minutes it never rose above 140.

    My guess is that there's no thermostat in the housing but I haven't pulled it apart yet to see but is it possible that it's got a 140 degree stat? I'm in the process of tweaking the choke to get it to completely open when the engine is warm but if it only gets to 140 I don't know if that's hot enough to fully open the choke anyway.

    Thanks.
    2008 Maxum 1800MX - 'Lottie-Da'
    1994 Proline 2510 - 'DrifteR ' <- project - ON THE WATER!
    1971 Concorde 27' - 'Little Angel ' <- sold

  • #2
    If you have a carb motor then it came with a 140 degree thermostat.

    If your in fresh water you can change to a 160 but not necessary
    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 Seadoo GTX
    Merc Adults Only VP Adults Only
    G-Dad always said "First Liar doesn't stand a chance"

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    • #3
      A 143 is pretty common. I run a 160 and have never timed it but it does take a bit to warm up. If there is none in there you will want to install one.
      83 Sunrunner 16.5 120 merc Alpha 1 drive SOLD 8/1/13

      1996 Crownline 202BR
      5.7l EFI 0f791070
      Bravo I drive

      GMC Yukon tow rig

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      • #4
        and you choke may be electrically operated not bi-metal housing operated
        NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

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        • #5
          I'm guessing you have a 140 deg installed. Occasionally mine gets blocked open with sand, etc after I back off a beach. Then I never get over 110 deg. 10-15 sec at WOT flushes it and I'm back to 160 deg.
          '96 Larson 174 SEI BR. 4.3LX 4 bbl Weber s/n 0F786604. Alpha One Gen II s/n 0F709315

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          • #6
            Yeah it definitely makes it to 140 but I'll double check it tonight. My choke is bi-metal spring operated but I may consider an electric upgrade since this thing is for the birds.
            2008 Maxum 1800MX - 'Lottie-Da'
            1994 Proline 2510 - 'DrifteR ' <- project - ON THE WATER!
            1971 Concorde 27' - 'Little Angel ' <- sold

            Comment


            • #7
              Originally posted by TBarCYa View Post
              Yeah it definitely makes it to 140 but I'll double check it tonight. My choke is bi-metal spring operated but I may consider an electric upgrade since this thing is for the birds.
              Someone must have switched the choke. Even my 1983 had an electric choke. The ones that I have seen with bimetal had a tube from the exhaust to heat them and it was old.
              83 Sunrunner 16.5 120 merc Alpha 1 drive SOLD 8/1/13

              1996 Crownline 202BR
              5.7l EFI 0f791070
              Bravo I drive

              GMC Yukon tow rig

              Comment


              • #8
                Your t'stat must have a small bypass hole in the flange to allow water to circulate past the t'stat and warm it up quickly.

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                • #9
                  If the boat has a 140 stat in it your temp may be normal. I find that with a 160 stat in my OMC it usually runs between 155-160 at idle and at most it will touch 175 after coming off plane but then cool back to 160 after slow speed running or idling. Get an IR Temp gun and check your readings, on the intake manifold right under the 'stat housing. This I find seems to corelate closest with the dash gauge reading, usually it's about 10* lower.

                  About the choke, I have had both the intake manifold heated choke (Rochester) and electric (Holley) my experience with them has been that the intake heated choke takes a long time to open unless you are actually running it on the water, if just idling on the water hose they take forever to open all the way. The electric chokes open almost too fast, they are just responding to the voltage applied to the choke heater and not what temp the engine is actually at (as do the intake heated chokes). You can in some cases convert to an electric choke but if it needs a full 12V to open it, keep in mind you will need to find a terminal on your alternator that provides 12V with the engine running, but zero with the engine off, even if the ignition is still on.

                  Also if you can get one for your engine, you can put a 160 stat in it, for OMC/Volvo engines that's all that I have ever found and I have not had overheating issues with the 160. Keep in mind that these auto based engines were designed to run much hotter (it 195* stats, so running temps of 195-210 or so are typical). However, in an open or raw water cooled engine which is what most of us have, due to the fact that the cooling water is not pressurized, you cannot run that hot, because you could get localized boiling in the hotter parts of the cyl head (ie like near the exhaust valve seats) if you were running that hot. The pressure cap in a closed system keeps that from happening.

                  Keep in mind that when we drove carbed cars, a normal part of the yearly tune up was cleaning the choke plate, pivot points and linkage. If they get dirty the choke spring may not be able to open it all the way. So before you change to an electric choke, clean up what you have, and see if that helps it to open.

                  Personally I'd rather have a manual choke on a marine engine due to the issues noted above, but the available conversion kits are not good quality.
                  Last edited by Lou C; November 8th, 2018, 08:30 AM.
                  1988 Four Winns 200 Horizon
                  4.3 OMC Cobra

                  98 Jeep Grand Cherokee 4.0 Selectrac
                  07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                  "While air doesn't freeze....rust never sleeps"

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                  • #10
                    Originally posted by Lou C View Post
                    If the boat has a 140 stat in it your temp may be normal. I find that with a 160 stat in my OMC it usually runs between 155-160 at idle and at most it will touch 175 after coming off plane but then cool back to 160 after slow speed running or idling. Get an IR Temp gun and check your readings, on the intake manifold right under the 'stat housing. This I find seems to corelate closest with the dash gauge reading, usually it's about 10* lower.

                    About the choke, I have had both the intake manifold heated choke (Rochester) and electric (Holley) my experience with them has been that the intake heated choke takes a long time to open unless you are actually running it on the water, if just idling on the water hose they take forever to open all the way. The electric chokes open almost too fast, they are just responding to the voltage applied to the choke heater and not what temp the engine is actually at (as do the intake heated chokes). You can in some cases convert to an electric choke but if it needs a full 12V to open it, keep in mind you will need to find a terminal on your alternator that provides 12V with the engine running, but zero with the engine off, even if the ignition is still on.
                    Agreed. Heat well chokes in a marine environment rust up and fail. On most heat well chokes on street applications, there was a heat sensitive flapper on one exhaust manifold which closed when cold and forced hot gasses thru the heat crossover in the intake manifold which resulted in faster warming of the intake manifold.

                    Some electric chokes run thru an oil pressure sensor, so they only get current when the engine starts.

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                    • #11
                      I have also seen aftermarket ones sold on quadrajetparts . com, that use a temp sensor that bolts to the intake. This may be better than the Holley style ones that tend to open a bit too fast.

                      Is this a Merc or Volvo engine you are talking about?
                      If Merc, then it should have a Weber carb and electric choke.

                      http://www.crowleymarine.com/mercury...cfm?mdl=LGBZIB

                      If a Volvo, then same thing, electric choke on a Holley 4160 it looks like to me....

                      http://www.volvopentastore.com/Carbu...view_id.778981

                      So if your choke is not working, then its either a bad choke coil or bad wiring to the choke coil. Check for 12V with the engine running at the choke positive terminal. Of course the other terminal must have a good ground. When these work, they open fast like in 3-5 min at most.
                      Last edited by Lou C; November 8th, 2018, 11:50 AM.
                      1988 Four Winns 200 Horizon
                      4.3 OMC Cobra

                      98 Jeep Grand Cherokee 4.0 Selectrac
                      07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                      "While air doesn't freeze....rust never sleeps"

                      Comment


                      • #12
                        I haven't had her out of the slip yet but it seems like the old school choke works just fine as long as I get the linkage adjusted properly. I'll probably check again tonight before taking her out this weekend just to be sure that it's adjusted right.
                        2008 Maxum 1800MX - 'Lottie-Da'
                        1994 Proline 2510 - 'DrifteR ' <- project - ON THE WATER!
                        1971 Concorde 27' - 'Little Angel ' <- sold

                        Comment


                        • #13
                          Originally posted by aimlow View Post
                          Your t'stat must have a small bypass hole in the flange to allow water to circulate past the t'stat and warm it up quickly.
                          Not needed on a BBC. there is a 1/2" diameter bypass line from the manufacturer.
                          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                          Past Boats
                          1970 Wooster Hellion - Merc 9.8
                          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                          What’s behind you doesn’t matter.Enzo Ferrari

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                          • #14
                            Originally posted by Scott Danforth View Post

                            Not needed on a BBC. there is a 1/2" diameter bypass line from the manufacturer.
                            The hole allows hot water to circulate better and melt the wax pellet sooner..sometimes the t'stat sits in a somewhat uncirculated water mass, even tho there is the stock bypass.

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                            • #15
                              Sign up today
                              you keep telling yourself that.
                              Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                              Past Boats
                              1970 Wooster Hellion - Merc 9.8
                              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                              What’s behind you doesn’t matter.Enzo Ferrari

                              Comment

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