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norton

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"1986 Mercruiser 190 HP - Engi

"1986 Mercruiser 190 HP - Engine idles fine but when I open it up and come to operating temp. the engine looses RPM's, oil pressure, bogs down and dies. When I try to restart the engine barley turns over likes there's a compression lock or something. When it cools down everything is fine again. Battery's good, water temp. good, thermostat good, impeller good, heat exchanger good, compression good. Someone suggested weights on mechanical distributor weak or stuck throwing timing off but haven't checked that yet. Any suggestions?"
 
"4.3 V-6, right?
Is your chok

"4.3 V-6, right?
Is your choke butterfly opening up all the way when hot?
What oil are you running?
Could be the coil breaking down after it warms up.
Plugs, wires?
Have you done a compression check?

Rod"
 
"Fuel filter plugged, bad gas,

"Fuel filter plugged, bad gas, needs tune-up, coil dying, condenser dying, carb flooding--needs overhauled, partial exhaust blockage."
 
"3.7 liter in-line 4 cylinder

"3.7 liter in-line 4 cylinder
Butterfly fully open - carb's been rebuilt 2 years ago
Plugs new - wires 4 years old
Compression good in all 4 jugs
new gas/filters/plugs/condenser
Coil - hmm -5-6 years anyway - might be that, I need to recheck timing advance too this weekend"
 
Sounds like an overheating pro

Sounds like an overheating problem...are you sure the temperature gauge is reading correctly...does the oil pressure drop in relation to engine speed or does it drop first and then the engine slows down???
 
""When I try to restart th

""When I try to restart the engine barley turns over"

Either weak battery, worn starter or as Bob suggests; overheating.

Fuel pump; is it original? Replace the cone filter in the dome? Test the output pressure.

Fuel tank; anti-siphon valve partially plugged.

"carb's been rebuilt 2 years ago"

Check the base gasket for a vacuum leak at 1200 RPMs. Replace base gasket if questionable w/correct gasket from Merc. dealer. Clean the flame arrestor.

Check the dist. cap for carbon tracking."
 
I'm starting to doubt my t

I'm starting to doubt my temp. readings and plan to replace both sender and gauge. I did suspect overheating also and replaced impeller and cleaned the heat exchanger both of which were not in bad shape. The fuel pump is original and could be the culprit. If it starts to fail could that cause the engine to run lean and thus the overheating? I'm putting everything back together (lower unit & exchanger) this weekend and firing it up. The trouble is it's on land and the yard manager wants to put it away so I might have to wait until spring to trouble shoot.
 
""fuel pump is original an

""fuel pump is original and could be the culprit. If it starts to fail could that cause the engine to run lean and thus the overheating?"

If it begins to fail, it usually is due to a tear in one of the diaphragms. The fuel enters the vacuum chamber of the pump and is siphoned out by the carb. via the clear sight tube. This excess fuel causes the engine to run on a rich fuel mixture and choke."
 
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