3.7 Merc will not turn over

[jjbritting]

While trying to start my 3.7 170 hp yesterday I could not get the motor to turn over. I used a fresh battery with 650 cranking amps. The crank turned maybe 1/8 of a rotation during the whole day-30 to 40 starting attemps.The oil was full and clean. 2 months ago it ran perfectly. I removed the plugs to relieve compression no differance. I loosened the year old starter hopeing the bendix gear was jamed but it was not. I then removed starter checked on bench seemed operate fine. Teeth on flywheel OK.Sprayed WD-40 into cylinders. Tried to turn with 3/8" rachet on crankshaft bolt would not budge. Closed system fluids were normal. I used 3 different batteries all were good. Is it possible something in the outdrive was preventing turn over? The oil was drained in the lower unit because I was getting ready to change the water pump. This has me stumped due to the fact that was operating so well just 2 mos ago.

 

[galaxy225]

Re: 3.7 Merc will not turn over

o.k sounds like your going threw ...what ijust got done doing.....i found that rings were frozen.....i took out spark plugs sprayed wd40 and used a three fine screws on the crank with a foot long bar and turned it that way and also had someone try and crank it.....i would also check point rotor codenser....coil...to see if you your getting spark....come to find out after i got rings unfroze my distributor it self was was off timing.........so good luck hope any info worked

 

[flashback]

Re: 3.7 Merc will not turn over

try to turn the engine over manually without the plugs in, shifter in nuteral, if it does not turn over, the next logical place to look is the timing chain, but first i would remove the out drive just in case the drive is jambed, and try it again before i tore the motor down.

 

[chiefmike58]

Re: 3.7 Merc will not turn over

jjbritting, if motor was turned over without water supplied to outdrive you may have melted impeller on lower unit freezing rotation. I agree with privious post, pull outdrive and see if motor frees up. One more possibility is that magnet on front alternator pulley has come loose(and they do) jamming against stator stopping rotation. Hope this helps.