4.3 merc . spring starup

samurai1988

Recruit
Joined
Jul 11, 2022
Messages
5
almost seemed motor seized after 4 or 5 try's
starter would not Engauge . replaced starter , did compression test ,
right bank all about 125
# 6 125 # 2 75 # 4 100
sprayed all cylinders with 4d 40 let sit
test #2 75 #4 zero all plugs out turned freely
#2 and # 4 added engine oil and let sit tested #2 125 # 4 zero
any ideas thoughts
thank u
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
12,696
You can pull the valve covers and disable the ignition & just crank it over briefly (don’t want it to start will make a big mess) to observe of the valves open & close. But it seems like the heads are coming off.
Any water in the oil?
Possibilities:
Leaky manifold to elbow gasket let water drip down & corroded # 4 exhaust valve
Blown head gasket
The 125 results are low too normal on these is more like 150-165 psi.
 

flashback

Captain
Joined
Jun 28, 2002
Messages
3,963
On My old 350 I had a rocker arm stud come loose. In those days they were pressed into the head but I don't think they are anymore.
 

samurai1988

Recruit
Joined
Jul 11, 2022
Messages
5
You can pull the valve covers and disable the ignition & just crank it over briefly (don’t want it to start will make a big mess) to observe of the valves open & close. But it seems like the heads are coming off.
Any water in the oil?
Possibilities:
Leaky manifold to elbow gasket let water drip down & corroded # 4 exhaust valve
Blown head gasket
The 125 results are low too normal on these is more like 150-165 psi.
no water in oil ... i think results are normal for this 4.3 at 125
but will check again on sites ... th u
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,591
Studs still pressed in

Normal compression numbers are 150 psi
 
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