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Author Topic:   Merc 1500 , Shut down. Electrical Problem?
JOHN W MAYO posted 11-20-2003 06:07 PM ET (US)   Profile for JOHN W MAYO   Send Email to JOHN W MAYO  
After hitting a big swell at about 25 mph, 5 seconds latter eng quite. Restarted ok,....suddenly died a few seconds latter. It did this about 30 times as I was trying to get back from the channel and back to dock with my Revenge. ended up getting a tow, (glad It quite before I made it 30 nm out. A check of the wireing showed it was missing much insulation. I replaced the wireing harness, and have got the engine running again. It quite again after the replacement of the wireing. But it will at least run. Does this sound like the coil, stator or rectifier problem? I cranked it up with the rectifer not attached during the change and it became very warm, and arched to to metal. I know now it should be grounded. What is the purpose of the mercury switch? any suggestion are apprecited in advance...........I hope to take the whaler out this weekend to Hatteras, but worry about dependablity of the engine. At least not worried about the Whaler itself. I have also had high voltage 16v-16.4vdc. A check of wireing connections showed all tight and secure. It showed this with either of the batteries I swithed to.
BQUICK posted 11-21-2003 11:12 AM ET (US)     Profile for BQUICK  Send Email to BQUICK     
Mercury switch will shut the motor down if it tilts up.

Sounds like a voltage regulator (rectifier) problem with volts like you are seeing.


Bigshot posted 11-21-2003 01:53 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Does it bog out or quit like you turned off the key? If bogging, try replacing the fuel filter/water seperator. If electric, depends on what wire you are talking about. There are a ton of things that can go wrong and old merc wiring is horrible, brittle stuff. Does this have the distributor cap being a 1500?
JOHN W MAYO posted 11-21-2003 10:29 PM ET (US)     Profile for JOHN W MAYO  Send Email to JOHN W MAYO     
It quite like an electrical switch turned it off, all of a sudden. not like a gradual fuel starvation.
The 150 hp 1500 has a distributor.
I took the wireing harness off as it was brittle wire with exposed wire and insulation gone. Replace the entire wireing harness with one i took off a 1400 140 hp.
Motor will crank now , but still will cut off as if you turned the swith off after it runs a few minutes.
I may try some of the other ikd parts off the 1400 but the coil. switch. retifier look different.
would high voltage in itself shut down the engine 16.4 v??
It is not likely the mercury switch could be bad is it? Could the retifier cause it not to run??
Thanks for the replies.
JOHN W MAYO posted 11-21-2003 10:34 PM ET (US)     Profile for JOHN W MAYO  Send Email to JOHN W MAYO     
the mercury switch. what does it do? Shut the engine down if the engine goes out of the water as in jumping a swell??
I will try and check it with an ohm meter.
Would the other parts..rectifier, switch, work if they are not made quite the same as on my current engine?
Sal DiMercurio posted 11-21-2003 11:06 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Your rectifier will not effect the way the engine runs at all, it's the charging unit for the engine.
If your getting 16 volts, your rectifier is working, if it wasen't working, you would have zero voltage or below 12 volts.
There are so many things that could cause the engine to shut down when it gets warm, my thoughts lean towards your stator or power pack.
Clark Roberts posted 11-22-2003 08:15 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
John, you may have a bad (intermitant..sp?) ground somewhere in elec. system. Check it out! Happy Whalin... Clark .. Spruce Creek Navy
PS> check out the key and kill switch circuits also
Bigshot posted 11-24-2003 01:35 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Disconnect the mercury just to make sure, not necessary anyway. If still acting up I would normally look at your powerpack but on that engine you have 2 so if one died it would still run like crap on 3 cyls for a while. Problem is I do not kow snot about the distributor engines. If like most cars there is a stator inside that is probably the culprit. On that engine it could also be under the flywheel. The parst you have on the 140 ar einterchangeable so start with one at a time and keep going. You can also check part numbers to make sure.
JOHN W MAYO posted 12-01-2003 03:24 PM ET (US)     Profile for JOHN W MAYO  Send Email to JOHN W MAYO     
Thanks for the info, I will check all ..........thanks
outragesteve posted 12-02-2003 03:59 AM ET (US)     Profile for outragesteve  Send Email to outragesteve     
I've had ALOT of experience with this 1500 Merc. Could be a few things: Bad ignition switch. Poor connection on harness plug on side of engine. (Wiggle it to see if engine misfires). The distibutor housing (part of distributor with the wires coming out) can go bad. It is a trigger, that fires the plugs through the cap. (Merc part # is 393-3736-A23) Also check the carbon in the distributor cap: They can get worn down and the spring tension doesn't always keep them against the rotor) I've also experienced a tach failing and causing the ignition to shut down. If the problem persists just sitting on the trailer, I'd be looking more for am ignition part failure than for a loose/intermittent connection. Lastly. the Mercury switch can cause a problem: I remove them. Good luck...
JOHN W MAYO posted 12-05-2003 09:21 PM ET (US)     Profile for JOHN W MAYO  Send Email to JOHN W MAYO     
Thanks to everyone for the good respnse to my question, I have check most now....
-replaced wireing harness inside motor cowling
-plugged in another mercontrol and wireing harness, switch,etc
-changed swicth box
-removed mercury switch
-replaced wires up to stator
-replaced rectifier (it was putting out 16.4 v, then 0
now with new one put out 13.8
-replacded coil
-chechecked all grounds I could find
-changed fuel filters and added another
-rebuilt fuel pump
-cleaned distributor cap / checked wires
and fininally change the distributor...this seems that IT MAY HAVE has not cut off while running on the trailer yet.
When I installed the distributor, I was very careful to keep every thing aligned. and the engine cranked right up. I do think the timing adjustment are off some, I did not have a DIAL INDICATOR to use, and have not used a timming light yet. Is a DIAL INDICATOR REQUIRED????
Would a timming light do it???
I understand that the timming is critical on this engine. I have used a shop manual to assist in all these changes. But do not have access to that dial indicator.

Any suggestion on adjusting those 3 screw on the plate attaached to the distributor of timming advance, idle, max advance???.......Thanks (I had to give shop manual back)

pamlico posted 12-07-2003 07:07 PM ET (US)     Profile for pamlico  Send Email to pamlico     
That dial indicator would be helpful in finding TDC for doing a timing check.
pamlico posted 12-07-2003 07:21 PM ET (US)     Profile for pamlico  Send Email to pamlico     
Try Precion Mfg. & Sales CO. INC. out of Clear Water Florida. for that Dial indicator. They should have one, I would imagine the price is kind of high my guess would be $75.00. They are expensive place to shop but they always seem to have those hard to find but badley needed tools.

FAX 1-727-446-1163


Steve Leone posted 12-07-2003 09:10 PM ET (US)     Profile for Steve Leone  Send Email to Steve Leone     
You can static time that Merc. With the inition on, and the timing advanced all the way with the pointer towards the timing marks just rock the flywheel back and forth. Make sure you diconnect the fuel and be carefull it does not start on you. Or you can just remove ALL the plugs. Ground the #1 spark plug to the block. The # 1 plug wire will fire each time you rock the flywheel. #1 spark plug should fire at the specified mark on the flywheel. Make sure you retard it 2% to make up for the alchohol in the fuel these days. You should also block the cross over hoses on the carbs with lead shot (12 gu. works best). Mercury Thunderbolt Ignition is Electronic. It uses a powerpack, distributor, and stator for your model. The trigger is mounted in the distributor. It is a 6 vane distributor (one vane for each cylinder). These are pretty bullet proof except for when the bearings sieze up or the trigger goes out. I doubt if it is the trigger as it would not fire at all if this were the case. My money is on the rotted wires. Those years were known for poor insulation on the wiring. They used real rubber (the kind from rubber trees) instead of poly based insulation. The other item to watch out for on those pups is the carb floats. The old style were made of foam and they would expand, thus sticking on the sides of the bowl. This would cause the carbs to overflow or "flood". The float would not rise enough to close the needle into the seat. This is remedied by replacing them with the new black plastic versions (available from Merc or Sierra). Steve Leone
Steve Leone posted 12-07-2003 09:16 PM ET (US)     Profile for Steve Leone  Send Email to Steve Leone     
Ps The spark advance screw should not be tampered with unless you know what you are doing. If anything you need to be turning it slightly in than out (to retard). This is the stop for the W.O.T. You do not want to go past the factory setting or you will blow a hole in the top of #3 piston. The idle screw is the last one you will need to touch and this needs to be done with the boat in the water with the engine warm. The idle will drop approx 100-200 rpms when the lower unit is submersed. Its go to do with exhaust backpressure (some outboards are "exhaust tuned").
Steve Leone posted 12-07-2003 09:17 PM ET (US)     Profile for Steve Leone  Send Email to Steve Leone     
pps If you blow it up I have a good one for sale for $1250
JOHN W MAYO posted 12-09-2003 07:59 AM ET (US)     Profile for JOHN W MAYO  Send Email to JOHN W MAYO     
Pamlico, thanks for the info on the dial indicator and where to locate it.

Steve, I have changed the wireing and you were correct, it was in very bad shape with the insulation but I am still haveing the problem of shut down. Your excellent notations of what to do is aprreciated and will try to set the timing as you described. Althought it shuts down so suddenly, like a switch,I think it is electrical, but, I am running out of things to check and the carbs will be next if the timming and distributor dont work. I will keep you in mind ref the eng you have.
Thanks again for all ideas to help from everyone.

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