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  • '72 Chrysler 55hp overheated

    Sorry for the long post. I am slightly above average in general engine repair, but a noob in the Marine area.
    I have a '72 Chrysler 55hp that I recently repaired the lower unit gears. The first time that I took it out all gears were fine but the shift linkage was slightly out of adjustment. Made the adjustment and went out at a small local lake. All was perfect. Run for 10-15 minutes at various speeds (lake rules is no wake but...). Decided to do some fishing so cut power and trolled to a spot. Smelled something, and noticed a lot of smoke coming from the cowl. After several hours of fishing, attempt Ed to start it up...nothing. pulled cables to change batteries. Noticed excessive load on the battery and sparking upon disconnect/connect. I found that both spark plug wires were melted to the head. One is toast, and I am waiting for replacements.
    When I got it home, I did some small investigation. First, the water pump impeller is disentergrated. Second, I disconnected everything except the starter. It works fine. Last , I reconnected everything. Then while reconnecting the battery, I again encountered the load and arching. I initially thought that it was under the flywheel, but maybe not. I took the plug wires off of the coils and the load and arching stopped.
    This brings me to my questions:
    1. Does the coil on this model stay hot, 12v direct, even though the ingition is off?
    2. How do I test for a fault in the stator?
    3. Is there something I am not considering?

    I cannot know the extent of engine damage nor if there is any beyond the plug wires until they are replaced. But I am wanting to ensure that I do not cause more damage through ignorance.


  • #2
    Welcome aboard, Paris.

    With it getting hot enough to melt plug wires, another wire or wires may have melted and are shorting to some place on the motor or shorting together.

    Since it was more than an overheat, China Syndrome comes to mind, insulation on the stator may have melted. Since you're arcing when hooking up the battery, start with disconnecting everything electrical under the cowl except the starter as you did. Then start connecting one at a time and arc check each time.

    If you have a meter, you could try this with the battery disconnected. Connect a meter across the battery cables, it will probably show a short, so start removing wiring one at a time again while looking for the meter to show no short. That should ID where the short is.

    BTW - Did you change the impeller after fixing the gears? My habit is to change the impeller any time I open the water pump unless it's very fresh. Impellers can take a set and harden over time. If it's reinstalled upside down from the original position, the vanes can break off with the reversed rotation.

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    • #3
      Model # ?-----Does it have 1 coil or 2 coils under the flywheel ?-------I am thinking you really need a wiring diagram and check all wiring.

      Comment


      • #4
        I thank you for your help.
        i did the disconnect check on the battery. However, only one other wire is connected straight to the battery and I am unfamiliar with the ignition wiring to continue to isolate items. Currently the is no load when I connect the battery. This may be due to a short having burned itself in the clear or by my disconnecting the spark plugs.
        The plug wires were pressed against the heads...not my doing... So the heat was not extreme, just higher than desirable. No paint discoloration or peeling. Wires that are 1/2" from the head show no signs of heat effects.
        I agree with your suggestion of other wires may have melted. I will re-examine those accessable. I believe that if this is the case, it will be the stator.
        Here is where I show my "noob". There is a black box with 4-8 wires attached. 2 or 3 wires go under the flywheel and the rest either go to the ignition multicable (to the helm) or to the battery (pos and gnd). Could this box have failed? It is close enough to have received high heat as it is above the head.

        Comment


        • #5
          Aside from having fried any electrical component that will be determined later, If the motor overheated badly to the point of having smoked worse than a chineese gang of heavy poker smokers, the cylinder head gasket could be already shot, regardless if having warped the head or not.

          Will need to retorque it to its factory specs, the same applies for the exhaust cover if having one, thermos and motor lower base gaskets. If all were severely overheated, better install new ones..

          Happy Boating
          Last edited by Sea Rider; March 25th, 2020, 12:09 PM.


          Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

          Comment


          • #6
            Your thread says 72 Chrysler 55Hp then it can be equipped with three different ignition systems.
            1, Magneto ignition.... two ignition coils, two condensers and two pair of points under the flywheel.
            2. Battery ignition ......two coils mounted beside the block at port side, two pair of points, two condensers and a stator under the flywheel.
            3. Magnapower ignition.....two ignition coils at the block back close to the head, two condensers and a stator under the flywheel. A "black box" CD unit mounted beside the block.

            Number 2 and 3 above need 12VDC from the battery to work and the 12VDC from battery controls from the keyswitch.
            12VDC at blue wires in ON and START position, not at OFF position.
            If power at OFF position at keyswitch the switch is bad.
            It sounds you have number 3 typ.
            You have the electric diagram at Maxrulesdotcom (Mastertech), technical spec., common wiring diagram, Chrysler/Force, Chrysler 55-65HP magnapower II (actually wrong from Mastertech, it is not a magnapower II CD).

            With this diagram you can troubleshoot and check what is wrong. The "black box" replaces the condensers and the points under the wheel are triggers for the box to dump power to the coils.

            Comment


            • #7
              Wow. I will check the torque of the bolts as suggested. I unsure of the exhaust cover... whether or not my engine has one.

              Nordin- I agree. From your description, my engine has the Magnapower (#3) type ignition. Thank you for the location of the wiring diagram. This will help loads!

              Comment


              • #8
                If you got it hot enough to melt the plug wires to the head??
                You need to do a compression test before you do anything else.


                Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
                ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

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                • #9
                  If the overheat has been fatal a cylinder compression test will only show a poor compression number due to the head gasket already being shot by excessive heat, the cylinder head has lost its factory torque specs or it's a combo of both situations. If the head retorque doesn't better the compression, install a new head gasket and torque it to factory specs.

                  But before doing so check if the cylinder head is aready warped, if so, will need to send it to a machine shop to have it machine worked (put straight even). Been on exact same overheat situation or even worse 3 times in a row due to kelp issues.

                  Happy Boating


                  Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

                  Comment


                  • #10
                    Originally posted by Paris Waterman View Post
                    Sorry for the long post. I am slightly above average in general engine repair, but a noob in the Marine area.
                    I have a '72 Chrysler 55hp that I recently repaired the lower unit gears. The first time that I took it out all gears were fine but the shift linkage was slightly out of adjustment. Made the adjustment and went out at a small local lake. All was perfect. Run for 10-15 minutes at various speeds (lake rules is no wake but...). Decided to do some fishing so cut power and trolled to a spot. Smelled something, and noticed a lot of smoke coming from the cowl. After several hours of fishing, attempt Ed to start it up...nothing. pulled cables to change batteries. Noticed excessive load on the battery and sparking upon disconnect/connect. I found that both spark plug wires were melted to the head. One is toast, and I am waiting for replacements.
                    When I got it home, I did some small investigation. First, the water pump impeller is disentergrated. Second, I disconnected everything except the starter. It works fine. Last , I reconnected everything. Then while reconnecting the battery, I again encountered the load and arching. I initially thought that it was under the flywheel, but maybe not. I took the plug wires off of the coils and the load and arching stopped.
                    This brings me to my questions:
                    1. Does the coil on this model stay hot, 12v direct, even though the ingition is off?
                    2. How do I test for a fault in the stator?
                    3. Is there something I am not considering?

                    I cannot know the extent of engine damage nor if there is any beyond the plug wires until they are replaced. But I am wanting to ensure that I do not cause more damage through ignorance.
                    if the motor got hot enough to melt plug wires, the bores and bearings long prior were toast. the wire insulation melts well above 350 degrees (polymer dependent). at 250 degrees, the oil started coking in the bearings and the rings started eating the bores.

                    the shellac in the windings under the flywheel would have started melting prior to the burn point of 180C (350F).

                    when you had the lower unit apart, you should have put a new impeller in the motor. every few years, new impeller, regardless if you use the motor or not.

                    with the suspected amount of damage to this motor from your thermal event, I suggest you start looking for a new motor.

                    this one may literally be burnt toast.
                    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

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                    • #11
                      Update...
                      Compression is good.
                      Located the short in a single wire.
                      Stator tests good.
                      Pulled plugs and engines spins freely (like a top).
                      Engine is now cranking and running perfectly!!
                      Thanks for all the help.

                      Comment


                      • #12
                        An overheat due to water pump failure, water intake ports blockage damages much less compared to an overheat caused by poor oil lubrication. In the first case the pistons will be locked against the cylinder walls, after it cools down will unlock itself and return to work as usual as in this post. PW, did you torqued the cylinder head, lower crankcase pan gasket or any other ?

                        When running perfectly, was tested while running in a barrel, muffs at idle whether at neutral or fast forward or when tested at sea at wot under the usual load ? BTW, good to read that the motor is back again into operation.

                        Happy Boating


                        Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

                        Comment


                        • #13
                          Sign up today
                          One last thing,
                          You said the impeller disintegrated??
                          The pieces might end up in the thermo and cause problems???
                          MAYBE???


                          Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
                          ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

                          In Scenic , Beautiful San Sebastian by the sea Florida

                          88 Bayliner 21CC 2001 Mercury 225 HP EFI

                          PLEASE,NO PERSONAL MESSAGES IF THE QUESTION CAN BE ASKED ON THE OPEN FORUM I WON'T ANSWER AS MY SYSTEM CAN'T REPLY TO YOUR EMAILS

                          Comment

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