temp gauge '88 Sorrento

S

ScottR

New Member
May 6, 2022
11
Boat Info
1988 Sorrento 21
Engines
Merc 5.7 w/VP 260 outdrive
Hi All,
just bought a Sorrento in great shape, but the temp gauge is dead. I've looked online and here, but haven't found any replacements. Any ideas?
Cheers,
Scott
 
Figure out if it's the gauge or the sender. Ground the sender wire if it pegs full it's your sender.
 
Great advice, and will do!
Thanks a bunch.
 
What size sorrento do you have. I have the 88 s240. He is correct. Disconect the wire and touch it to the block. Ifnit jumps to full its good. Its most likely the temp sensor in the thermostat housing. Easy fix. Also invest in a temp gun. Will let you know when fixed if guage is spot on
 
Howdy,
it's a 1988 sorrento 21' bowrider with 5.7L/260 VP. One owner 179 hours on it and covered it's entire life. carpet and upholstery is all in great condition. need to buff the exterior finish and good to go. First boat for me, grew up on the Lake (Owasco in NY), so am very excited. Picking it up tomorrow 5/18 and will then diagnose that gauge/sending unit (I'd be surprised if if wasn't the sender), and will check back here once I get that done. Great suggestion on Temp gun, will do for sure.
thanks all!
 
One thing I found on a couple of Mercruisers I worked on was that someone had removed the thermostat housing, for what ever reason, and did not replace the gasket with the proper one that had the two brass rivets in it.

They used a standard automotive gasket and silicone sealer. That failed to ground the housing correctly and caused the sender / gauge to go funky. I installed the proper gasket and all was good after that. Easy to test to see if that is the problem.

Need to use the proper gasket, or add a bonding wire from the housing to the engine.
 
Figured out it was the sender, so replaced. New problem that I can't seem to find much on...
when key is turned to on, the automatic fire system alarm goes off, even when it is cold. I ran the blower for a couple minutes and tried again, but the alarm went off again. Any experience/thoughts?
cheers
 
Oh, I may have mixed terminology; it's the automatic fire system alarm. It went off last time it was run (when I was supposed to take it home) and dealer found out the impeller was bad so they replaced it. We just assumed it was the fire system alarm. got it home, turned on the key and an alarm went off, not really sure what the alarm is for actually, just assumed it was for that. Now that I think about it, I'm not sure what that alarm sound is actually for... It didn't happen the first test drive, just on the latest one.
 
Well it's not for that. With a boat of that age it's probably overtemp, low oil or drive fluid. They can be disabled 1 at a time to figure out which one it is.
 
The only alarm i know of on that boat is overheat alarm. Fie system is just a green light on fash. It does not have the extra canaster for drive oil so it domt have that either. Not sure what you are hearing. Might have to start it and track down alarm. Overheat alarm is inder dash and a small disc looking thing
 
No drive oil tank, leaves low oil pressure and high temp alarms. Have seen some people put a silence switch on the alarm for when ignition may be on, but engine not running. Problem is, they forget to turn the switch off / alarm on.

No alarm on the fire boy / green light.

In post # 10, he mentions the mechanic changed the impeller. Overtemp alarm.
 
Thanks all for the input! Reading the Merc manual, there is an 'audible alarm' that sounds for those things but also comes on if you have the key on and don't start within 7-14 seconds, sort of a test. I haven't started it yet (was doing cleaning and prep) and will get it in the water and see what happens. I'm suspecting it was that timing/starting thing, as the boat had a full maintenance on engine, outdrive, impeller, which should've removed most of those potential causes, presuming they did the work correctly. Will report back shortly once I get it in the water.
 
My 95 keeps blaring if you don't start engine. Sees low oil pressure. Shuts up as soon as engine starts.
 
Thats 95, remember this is 1988. Hair bands, spandex on men, and miami vice made sense. Not boats
 
Hi All,
Just wanted to shoot an update. Launched for the first time 2 weeks ago and started up perfectly and ran great! Thanks for all the helpful replies, greatly appreciated. Finally getting summer weather up hear in WA so we're all excited to spend time on the water.
cheers,
Scott
 
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