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Alternator - Mercruiser 228

J

jackman

Contributing Member
Engine suddenly died after I had been out for almost an hour and would not re-start. Sudden cut no spluttering. Would give a kick and die again when I tried to re-start. Got tow back. Checked battery next day with multimeter and showed 12 volts. Engine started and I ran it at 800/900 revs and meter showed 13.8 volts. Increased revs to 3500 but meter still showed 13.8 volts. Would this indicate a faulty alternator? This was whilst tied up in marina. I couldn't do any checks at time of incident as I did not have the multimeter with me. Any advice appreciated.
 
Your only one volt down, i pondered that over and over one volt why ?

You have dirty connections ? Disconnect the battery, follow the neg cable from the battery to the ground on the block. You did not give any info on make, model, year.

Usually the ground is close to the battery and maybe a thru bolt to the motor and bell housing. Again i would have told you more if i had more info.

Still with the battery disconnected, inspect the ends of your battery cable, maybe it's green under the rubber end, understand.

The battery lugs clean, use a steel battery brush and clean them, they might look clean do yourself a favor clean them.

Ok follow the pos cable to each connection, starter, temp gauge, etc. every connection.

Don't miss the coil. Don't get lazy take your time you want them all clean and shiny.

Your wires coming off the alt. good. The main barrel plug pull it apart what does it look like in there.

Still if there are fuses like a omc then take apart the fuse holder mine were green and i then redid my whole harness that day. That was the last straw on my boat, with old wires.

The connection under the dash to the key and gauges good. Clean them also.

Hook back up the battery. And run it.

If it happens again at that moment take a spare spark plug yank a plug wire and hold the plug to the block and find out if it's spark or fuel or missing.

See now you have a good electrical system, if it happens again it might be fuel.
 
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Thank you both for your replies. Mercruiser 228 engine 1978 vintage. Motorola alternator. Went back to boat the day after I broke down and it started immediately. I ran the engine for one hour whilst moored and took the revs up to 3500, in neutral obviously. I also ran it in ahead and astern against the mooring lines and did not encounter any problems.. Ammeter needle was steady as it had been on the day I broke down in central vertical position. I connected battery to a charger and it showed battery as being fully charged. BtDoctur I was out cruising when the engine suddenly stopped without warning. When I tried to restart it, it turned over very weakly and ran for a split second before dying again. Chiefalen I will follow your suggestion and check/clean all connections and have a spare plug handy in future. I had a full tank of fresh fuel on board by the way. Would you expect the fact of being 1 volt down for the engine to die suddenly? Seems strange the fact that it now appears to be running normally. Thanks again for the replies. Any further info' would be gratefully received.
 
check the main harness plug at the engine, loosen clamp, pull and WD the plug, re-insert and tighten clamp.corroded connectors will do this.
 
I forgot to add that when I took the spark plugs out after running on mooring the plugs were a dry light brown colour. Also when the engine packed up I was gradually increasing the revs from 2000 and it suddenly cut when I reached 3400 if that has any bearing on the problem. Thanks for your suggestion BtDoctur
 
Could anyone tell me where to exactly the main barrel/harness plug is located on the engine? Chances are that when I return to the boat I won't be able to find it!
 
mounted is a few places, on the riser with the shift cables, on the rear most part of the intake, near the carb. look for the main wiring harness from the transom and follow it.leads to a big plug about 1 -1/4 dia.
 
jackman said:
Engine suddenly died after I had been out for almost an hour and would not re-start. Sudden cut no spluttering. Would give a kick and die again when I tried to re-start. Got tow back. Checked battery next day with multimeter and showed 12 volts. Engine started and I ran it at 800/900 revs and meter showed 13.8 volts. Increased revs to 3500 but meter still showed 13.8 volts. Would this indicate a faulty alternator? This was whilst tied up in marina. I couldn't do any checks at time of incident as I did not have the multimeter with me. Any advice appreciated.
Click to expand...

check all wiring/fuses/conectors/lugs for corrosion and security...

13.8volts with a 1 wire alternator is normal.

your problem was engine suddenly cut out /died... engine was cranking but would not run ...

also check distributor wires..resistance wire to coil/connections...
 
Maybe the gauge is wrong. But you should be getting over 14. Check it with a accurate gauge.

I ain't gonna get into a pizzing match, if you rev it over 1000 rpm and the gauge reads under 14 something ain't right.

It took me more the 15 minutes to type the long post, maybe i'll stop people don't listen.

THE MAIN GROUND ON THE BLOCK CHECK IT, CLEAN IT !
 
OK you guys missed something here.......

battery 101

a charged static battery should show 2.1 volts per cell that = 12.6

a 12 volt charged battery is low and on the verge of a dead cell.


also he states he has a amp meter in his dash..............YUK!!!

Sounds like you guys are right with a bad connection and the lack of starting vs cranking explanation...........
 
chiefalen said:
Maybe the gauge is wrong. But you should be getting over 14. Check it with a accurate gauge.

I ain't gonna get into a pizzing match, if you rev it over 1000 rpm and the gauge reads under 14 something ain't right.

It took me more the 15 minutes to type the long post, maybe i'll stop people don't listen.

THE MAIN GROUND ON THE BLOCK CHECK IT, CLEAN IT !
Click to expand...


unless this meter he used is top quality professional meter the accuracy to a few tenth's of a volt is no big deal...13.8- 14.25 its all good..over 15V or under 13v its bad...
 
A good way to test a charged battery is to have it load tested. You can do it in the boat by just turning on all of the accessories for a few minutes. A good battery should hold a charge of at least 11-12 volts after a few minutes.

I also like to check each cell w/a 5 ball battery tester. Insert it into each cell and draw out some acid.. The # of floating balls tells you the amount of charge per cell. They should all be the same. If there is a dead/dying cell it will have dark acid in it and few balls floating.
 
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