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Sudden power loss 60hp Johnson

69boo307

New member
"Hi, writing about my 1990 60h

"Hi, writing about my 1990 60hp again. I've been working on this thing for a good 4 months and I'm about ready to turn it into an anchor!

Problem is, the boat will start and run well for about 5 minutes cruising at say 5k rpms, then suddenly the rpms will drop as if I just pulled back the throttle. It runs very smoothly to that point, and is not sputtering or missing or anything now, it simply does not respond to the throttle after that happens. It will not want to get back to cruising speed again and will barely be able to plane the boat off.
things I've done recently:
-rebuilt and cleaned carbs
-replaced fuel lines
-new plugs
-new powerpack
-compression good, 120 per cylinder
-sparks over a 7/16" gap pretty well
-Bulb is not slack when the failure occurs
-gas is fresh, no water in the gas, tried with different tanks and fuel levels.

If it is possibly ignition, I have not yet inspected the stator with the flywheel off. I also am wondering about the fuel pump?

Any ideas are appreciated!"
 
"it sounds like u r dropping a

"it sounds like u r dropping a cylinder...also,i would ck the wires on the timer base for raw areas grounding out..ck your spark and compression........now,run 2 spark test,one w/timer base at idle,then,..move to wide open throttle,and re-test,u will need a remote starter sw,watch the prop."
 
"My E175 did the same thing wh

"My E175 did the same thing when I took it out the last time..
I got up to WOT, ran about 45 mph for a minute or so then a sudden loss of power, and the engine bogged down like it was flooding out..

When I got it home, I removed the bypass covers (intake side cylinder covers) and found #1 piston rings seized and a piece of the piston deteriorated down into the ring grooves.

I had found a small piece of aluminum on the #1 plug, that's why I looked at 1,3,5 pistons first.."
 
"I don't think I have some

"I don't think I have something that severe going on, it has excellent compression on every cylinder and the plugs don't look too bad. I have noticed that the bottom cylinder #3 plug looks a bit more fouled than the others. If the ignition is dropping a cylinder I'd suspect it's that one."
 
"jwbmarine, can you describe w

"jwbmarine, can you describe what you mean by the spark test with the timer base? I assume you aren't saying to go WOT with the engine out of the water?"
 
"I think I have traced the pro

"I think I have traced the problem to a faulty ignition coil on cylinder 3. I traced all the wiring and connections with the timer base, powerpack, etc, and could find no problems.

I went out to the lake armed with tools and a new ignition coil, and ran it until the problem presented itself, then checked the plugs. #3 was very wet and oily. A quick cranking compression test showed it still had good compression, around 115. I put a new coil on that cylinder, and then ran it hard down the lake. I ran it for a good 20-30 minutes and it never missed a beat.
Here's hoping that solved it. The ignition coil I removed was cracked in the epoxy stuff on the back of it and the outside rubber coating was separating. I think I'll replace the other 2 while I am at it, they are in similar condition."
 
"that is w/eng OFF..to see if

"that is w/eng OFF..to see if timer base wires are raw,and grounding at or near WOT.
cracked coils can,and do arc to nearest ground,..and,moisture can cause prob....repl any that r cracked."
 
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