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View Full Version : Temp issues only when acc switch on?


brantley16
07-22-2013, 11:50 AM
ok guys,
I got a 91 PS 190 indmar motor. This past weekend the high temp alarm went off while @ idle and I was pegged at 220. fearing trouble, I killed the blower.....and presto, temp dropped back to 160. any switch I turned on, bilge, blower, radio, acc, caused it to jump to 220 turn them off and no problem.....motor is not hot. is it my sending unit?

Thanks

thatsmrmastercraft
07-22-2013, 12:08 PM
I had a similar problem in my '77 2 weeks ago. I removed my fuel tank to work access swim platform bolts and boogered up my ground for the blower during re-installation. My temp gauge and oil pressure gauge both registered higher by 20 degrees/pounds by backfeeding to a suitable ground. come to think of it, my fuel gauge was off too.

brantley16
07-23-2013, 02:13 PM
ok im leaning toward a grounding issue with my main ground. any ideas where to start looking?

LYNRDSKYNRD
07-23-2013, 02:21 PM
All of the switches may share a common groiund with a jumper between each switch. I would start with the main ground wire connection coming from the switches and work backwards from there checking the switches seperately.

thatsmrmastercraft
07-23-2013, 03:17 PM
All of the switches may share a common groiund with a jumper between each switch. I would start with the main ground wire connection coming from the switches and work backwards from there checking the switches seperately.

Makes sense.

brantley16
07-29-2013, 04:38 PM
i got more...
ok this weekend I cleaned all my connectors behind the dash in the "top level" of the dash paying attention to trace the ground wire until it goes into the second level of the dash around the steering column. that's where I stopped hoping to avoid pulling the driver seat so I could get my fat *** up under the console. took the boat out for a spin. all acc switches in the off position boat warmed up to a normal 160 deg. while out running it spiked and fell between 180-160 depending on what acc switch I needed to turn on. as I was moving into the boat dock I hit the bilge switch and it shot up to 220 and the alarm sounded off. turned it back off. put the boat in the hoist and raised it up. with the key off I hit the bilge switch to pump out any water and the temp gauge spiked to 220 and stayed for about 20 seconds then dropped back to the lowest reading. thought this may help with any thoughts. I guess the plan is to get the seat out and follow the ground on out but, replace sending unit etc. any help would be huge.

thatsmrmastercraft
07-29-2013, 04:51 PM
Several possible scenarios:
1. Ground for bilge is bad and main source for backfeed.
2. Bilge pump is full of crud and results in high resistance in circuit. May need to backflush bilge pump.
3. You have several bad grounds that need to be fixed.

I would spend time troubleshooting this in the driveway running off a hose. Misleading readings from a temp gauge are never any good.

brantley16
07-29-2013, 05:10 PM
sounds good. Im an not sure how I should backflush the bilge. other than puttn the hose up to the side of the boat and forcing water through there. I have looked in the bilge and its VERY dirty in there! lol like black!

thatsmrmastercraft
07-29-2013, 05:11 PM
sounds good. Im an not sure how I should backflush the bilge. other than puttn the hose up to the side of the boat and forcing water through there. I have looked in the bilge and its VERY dirty in there! lol like black!

Yup, that's it. Not too much pressure. If it's clogged up you may get wet.

brantley16
07-29-2013, 05:16 PM
bilge has always worked fine and is working now. ill do that, and continue to trace the ground wires on out. still haven't found the grounding bar that the mechanic told be to check. all the acc switches seem to affect the temp gauge at different levels. guess ill throw in a sending unit as well. its starting to piss me off though.
thanks for your help.

brantley16
07-29-2013, 05:18 PM
I guess I could try a new thermostat as well?