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1986 Vanguard with 140r mercruiser - quits after 2 hours of pulling single person tube

M

mgquinton

New member
Hi

I have a 1986 Vanguard boat with a 140r mercruiser engine (raw water cooled).

Problem: Boat runs fine while pulling tub for about two hours and then quits. If I let it sit over night it will work the next day as if nothing had happened.

Had the boat serviced last year by a marine tech and replaced the fuel pump and the ignition coil but it didn't solve the problem. Had gear oil changed and no water in it.
Tried new tank of gas and still have the same problem. Temp guage only goes up to half way line. Extremely frustrated.
 
mgquinton said:
Hi

I have a 1986 Vanguard boat with a 140r mercruiser engine (raw water cooled).

Problem: Boat runs fine while pulling tub for about two hours and then quits. If I let it sit over night it will work the next day as if nothing had happened.

Had the boat serviced last year by a marine tech and replaced the fuel pump and the ignition coil but it didn't solve the problem. Had gear oil changed and no water in it.
Tried new tank of gas and still have the same problem. Temp guage only goes up to half way line. Extremely frustrated.
Click to expand...

Ayuh,.... When it Quits,.... Pull the Spark plugs,....

If they ain't Sparkin',... Check for power at the coil's (+) terminal,...
 
The motion sensor and control unit determine spark.
They are sparkin' engine starts and then dies immediately.
Click to expand...
Assuming that fuel delivery is not the issue then one of the two is dropping out. Attaching a spark test board to all four plug wires when it dies will tell you if the two are working. Cranking the engine for several seconds while observing the board will show consistent loud blue snapping spark if they are working. The control unit is a $750 item while the motion sensor is NLA. I don't know if there is a one wire complete ignition distributor replacement for your engine.

What you can do is a complete examination of every electrical connection of the ignition circuit. You are looking for corrosion on a plug pin, darkened plug pins = overheated connection, loose wiring or anything out of kilter. Run the wires from one end to the other between your finger nails. You may feel a break, lump or hard spot which can be a point of failure. I remember a few years back that one member found a break in the wire in a harness by searching in this manner. Take your time and be deliberate. You can also ohm each wire in the harness while performing a wiggle test. There is a diode in one of the harnesses...don't remember which one. It will show up as resistance in one direction and an open circuit in the other direction.
 
86' had points in the dist.

Want to fix this ? It will take some time but you will have to do some work.

Disconnect the battery follow the neg cable to the main ground on the bell housing it is a thru bolt on the back of the housing is the nut take it off clean the cable and the nut examine the cable end.

Now follow the pos cable and at ever juncture remove and clean the connection, don't miss the starter. There is a main resit button and a fusible end on or on top of the starter.

Disconnect the main barrel plug it is held together with a spring clip.

Look inside the plug and see if there is green... green is bad.

So what your looking for is a bad end at the battery or the ground etc.

Next take off the dist cap and go thru it also, look for a wire grounding out. Points in good condition and the weights moving freely.

Please check your tank vent that it is clear.

Post back when your done !
 
Master mechanic said:
86' had points in the dist.

Want to fix this ? It will take some time but you will have to do some work.

Disconnect the battery follow the neg cable to the main ground on the bell housing it is a thru bolt on the back of the housing is the nut take it off clean the cable and the nut examine the cable end.

Now follow the pos cable and at ever juncture remove and clean the connection, don't miss the starter. There is a main resit button and a fusible end on or on top of the starter.

Disconnect the main barrel plug it is held together with a spring clip.

Look inside the plug and see if there is green... green is bad.

So what your looking for is a bad end at the battery or the ground etc.

Next take off the dist cap and go thru it also, look for a wire grounding out. Points in good condition and the weights moving freely.

Please check your tank vent that it is clear.

Post back when your done !
Click to expand...


All Done, No issues found.
 
Pull the fuel pickup tube there may be a screen on the end of the tube, make sure it's clear and the anti-syphin valve is clear.

There any cracks in the pickup tube, meaning is the tube drawing from the bottom ?

You do have points ?

you checked all the fuel line ? No cracks no air getting sucked in ?

You checked the filter in the fuel pump and the filter in the fitting that enters the carb ?

You have the original fuel hose maybe it degraded internally and a flap is closing your fuel off.

You have a dead mans switch... a lanyard that clips to you from a man overboard switch... if yes cycle it a few times and or bypass it for now.

post back !
 
Last edited:
I stand corrected...thank you. It would be nice to have engine serial numbers posted in the beginning.
 
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