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voltage drop

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redsnapper386

Regular Contributor
guy's, motor was running but idled rough.i installed new gauges,solinoids,battery,along with new motor,starter,alt,thunderbolt-4 dist,coil ,sensor,all wires checked,and clean.now motor turns over nice,but i noticed the volt meter was dropping down to zero. also noticed that when i operate the tilt motor up and down the volt meter dropped,and some gauge lights dimmed. i have run all tests that manual advises to no avail.most parts and componets are new or rebuilt.fuel delivery all good.have not replaced 50 amp breaker,turn key switch,battery switch,shift interrupt switch.the pin harness at motor is good,all plug ins good.any directions needed.thanks in advance.1987 sea ray,25 cc,350-300 hp. a-1 .
 
Check for good tight connection at the starter and main ground. Is the alternator charging? Has the battery been properly tested? Common mistake is to over tighten the clamp (if you have one) of the engine harness plug. This will distort the plug and cause intermitent pin contact. If you know how to do a voltage drop test with a meter, check when the symptom appears. Also try the wiggle test with the engine running. Wiggle every wire and connection until the issue arises and that area will likely be the issue.
 
yes,battery checks good.will go to pin next.also i have a good check out now at the dash panel,found some ground wires crossed.my fault,but engine will still not start.will start more tests and will post back.thanks guys.
 
Not start? Is this new? Not mentioned in your first post! Engine cranks over but won't run? Need to be a little more specific.
 
redsnapper386 said:
yes,battery checks good.will go to pin next.also i have a good check out now at the dash panel,found some ground wires crossed.my fault,but engine will still not start.will start more tests and will post back.thanks guys.
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Grounds, grounds, grounds....... Verify all ground connections are as close to perfect as possible. They can be the cause of all the things you are describing. Connect one lead of voltmeter to battery negetive and touch other lead to each and every ground connection (even the negetive of a second battery, if one is installed) and the engine block, when as many electrical components as possible are running. If there is anything approaching a half a volt between any of the connections, then there is a grounding problem that needs corrected, as it will likely only get worse.
 
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woodieman,sorry for late repost.yes i have a new issue.now motor turns over strong with new full charged battery.will not fire.i am in process of checking all grounds and move on to igniition.my boat is a 1987 sea ray with a major rebuild in progress.i suspect a short in the mix at this time.i am told to replace key switch,battery switch,50 amp breaker which i found a crack in.these are still original parts and should go any way.it is strange that the motor ran fine on the hose for check out after install and a few times after.it seems like as one fixes one area of a boat it makes another area weak.i appreaciate all input .i have to say at this point i am stumped.thanks.
 
where did you get a NEW thunderbolt-IV distributor? module, too?

The normal allocation (voltage drop) across a (high current) connection is 0.2 VDC; typically it will be much less or lots more. Don't forget to make sure the dedicated ground for the alternator is still being used and is not corroded.

I'd also slow down and stop changing 1/2 a dozen items at a pop; one at a time helps to maintain insight as to which helped and whcih didn't.
 
Maybe to late now. But i would have went with a hei unit. It has the coil built in. There are kits with the wires all in one box.

You just install the unit all one piece and one wire in one wire out and one wire to the tach.

Total of one hour work maybe, last one i swear i was done in 15 minutes with the motor purring.

My way it would take all the bullchit t-bolt system out of the boat.

Like i said maybe to late now.
 
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