$25 gift card to who can figure this one out.

[jkoenig1980]

Ok so my brother left me this ski boat while he was deployed. Its a 2000 Sea Ray 180 with a Mercruser 3.0l I/O, anyway the here is the history on the boat. The motor was rebuilt 2 years (failed to winterize it) ago before he was shipped to South Korea it has been sitting from that day till recently.

So the first time I take it out I notice the Temp gauge moves hotter and hotter till it pegs at 220. I get it out of water thinking it is over heating.

I replace. Impeller (gear lube too), Temperature sender, thermostat.

Nothing changes. The temp gauge will read 130 regardless if it has been sitting an hour or a week 130 is as low as it will go. and when the motor cranks up it slowly works its way to 220 or pegged hot.

So I go buy one of those laser temp guns. With the gauge pegged at 220 I cant get a reading over 170 anywhere. Im checking around the thermostat housing, hoses, block ....ect

So I keep that temp gun in the dash. Pull the gauge take it to marine max to order a new one and hit the lake. Full throttle, tubing, skiing, fishing...she runs like a top for days no problems.

Come home new gauge here....Install..off to lake..same problem.

so I bring it home and this is what i just did here is the riddle.

I left the new gauge installed. On the back of the gauge there is a power wire, ground wire, and wire that goes to the sending unit (Tan wire).

The OLD gauge I ran the power wire strait to the battery + and the ground to the battery - and a green wire to the sender.

So basically i could read either gauge by switching the wire on the sender.

I started the motor and watched them both peg out 220 deg.

Frustrated I kill the motor pull the sender out letting the hot water behind the sender pour in a cup. I put a thermometer in the water 168deg....

I dont have a ^$#%& clue what to do next.

 

[Eric 3.7LX Alpha 1]

Re: $25 gift card to who can figure this one out.

maybe the sender is NG

 

[ac0j]

Re: $25 gift card to who can figure this one out.

The sender is bad, or the ground it gets from the motor is different than the ground the gauge gets from the battery. Clean all battery connections at the motor. ALSO, the sender wire could be bad, adding resistance to the reading.

 

[fishrdan]

Re: $25 gift card to who can figure this one out.

The temp gauge will read 130 regardless if it has been sitting an hour or a week 130 is as low as it will go. and when the motor cranks up it slowly works its way to 220 or pegged hot.

Is the gauge good, sounds bad to me? It should drop lower than 130, IE: 130* on the gauge is really a stone cold engine, 220* on the gauge is really 160*.

130 to 220 is a 90 degree spread. 70 degree ambient temp plus the 90 degree spread is 160*,,, the engine should run around 160*....

adding resistance to the reading.

Somewhere along the circuit there could be added resistance, loose wire, corrosion on a connection, poor ground. Check the engine main harness bullet connector and see if everything is clean and tight, no corrosion or water in the connector. There should be a hose clamp around the harness connector to keep it water tight.

 

[Volphin]

Re: $25 gift card to who can figure this one out.

Bad ground my friend. Happens all the time.
Thanks to your bro for his service.

V

 

[Samjo]

Re: $25 gift card to who can figure this one out.

Since it did it from the first time you ran it....is there any chance your brother changed the sending unit in the past?

If so....the sending unit might not match the gauge properly, especially if he just took the old unit to a parts store and matched one up.

I'm no expert, but different gauge manufacturers, might design their gauges to work at different resistances. For instance a Stewart Warner sending unit might not read properly on a VDO gauge. I'd replace the sending unit from OEM and see where that took me.

BTW....if my diagnosis turns out to be correct....turn that $25 into something your brother could use, and send it to him. Thank him for his service.

 

[jkoenig1980]

Re: $25 gift card to who can figure this one out.

Since it did it from the first time you ran it....is there any chance your brother changed the sending unit in the past?

If so....the sending unit might not match the gauge properly, especially if he just took the old unit to a parts store and matched one up.

I'm no expert, but different gauge manufacturers, might design their gauges to work at different resistances. For instance a Stewart Warner sending unit might not read properly on a VDO gauge. I'd replace the sending unit from OEM and see where that took me.

BTW....if my diagnosis turns out to be correct....turn that $25 into something your brother could use, and send it to him. Thank him for his service.

I been wondering the same thing. The gauges are teleflex seherra series. The one they sell now is a 120 to 240 gauge the one I have is a 100 to 220 and when I bought it it had to be ordered from sea ray to get the correct 100 to 220 gauge.

As far as the bad ground. That's why I ran the second gauge strait off the battery and its reading was the same as te one on the dash.

 

[Fishermark]

Re: $25 gift card to who can figure this one out.

Did you put teflon tape on the sender? If so, that may be your problem. The sender needs to ground to the block. Permatex makes a good sealer for the threads.

Take the sender wire and ground it out - see what the gauge does.

 

[Don S]

Re: $25 gift card to who can figure this one out.

Sounds to me like you have the wrong sender in it, or a defective one.
It should test like this.