1998 5.7 merc temp issue. Please Help!

[clerihew82]

OK im narrowing down my overheating problem. I have a 1998 Mercruiser 5.7 serial OL029850 with a new SEI 116 outdrive with new impeller. Last weekend my gauge was showing about 190 degrees. Its a new to me boat so i didn't really know what to expect on the temperature. Today i got me a infrared thermometer and started shooting some temps. I had it on muffs and let it get to operating temp and here's what i came up with...

port side riser-95 deg
starboard riser- 109 degrees.
Thermostat housing on top- 95 degrees
base of the thermostat housing -158 degrees.

I put a new thermostat last week. What would be next?? temp sender?? gauge??

 

[90stingray]

Re: 1998 5.7 merc temp issue. Please Help!

Are these temps at idle? I would change the impeller since its new to you... that way you know its fresh.

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

The impeller is new. I purchased the new outdrive and put it on so i know it has a new impeller.

 

[90stingray]

Re: 1998 5.7 merc temp issue. Please Help!

alright... I thought maybe the previous owner told you it was new. Anyhow, are the temps at idle? What does it do if you rev it a little? What t-stat you put in?

 

[Bondo]

Re: 1998 5.7 merc temp issue. Please Help!

Ayuh,... Sounds like a gauge issue to me...

 

[NHGuy]

Re: 1998 5.7 merc temp issue. Please Help!

So did you get these numbers when the gauge said 190? I assume so. To test the gauge, 1st disconnect "S" terminal then turn on ignition switch (no need to start just to power gauge). The needle should go to it's lowest value. Turn off power. Now put a jumper wire between the "S" & "G" terminals. turn on the ignition, the needle should go to full hot. If the gauge does not do both of these things it needs to be changed.
It's also smart to check that there is a really good ground connection to the thermostat housing. You can test it by checking for continuity between the housing and any ground.

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

I put a 160 degree thermostat in. I guess i will test that gauge. Is there a way to test the sender for ohms 1st before i do the gauge?

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

i think you can test ohms on the sender.. Does anybody know the readings it should be? I found different things around the internet but haven't got a clear explanation.

 

[Incorrigible]

Re: 1998 5.7 merc temp issue. Please Help!

I know your frustration. I had a similar experience after replacing my lower unit. My problem turned out to be from the installation of replacement bellows. When the new bellows were installed, the hose between the lower unit and the boat was replaced. Turns out one size doesn't fit all. When the lower unit was in ANY position other than fully down, the hose would kink, cutting off part of the water flow to the engine (and thus the over heat) Never FULLY overheated, due to SOME water getting through. You said you got the boat to operating temperature and then started taking readings with a thermo/laser. What was the gauge reading when you were taking the measurements?

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

theres a pic in my first post in this thread. about 195 degrees.

 

[Don S]

Re: 1998 5.7 merc temp issue. Please Help!

i got me a infrared thermometer and started shooting some temps. I had it on muffs and let it get to operating temp and here's what i came up with...

port side riser-95 deg
starboard riser- 109 degrees.
Thermostat housing on top- 95 degrees
base of the thermostat housing -158 degrees.

Those temps are exactly what you should be seeing with a 160? thermostat.
Either your gauge or sender is off. Here is how to test the sender.

 

[produceguy]

Re: 1998 5.7 merc temp issue. Please Help!

If that doesn't work maybe a new circulator pump.

 

[Bondo]

Re: 1998 5.7 merc temp issue. Please Help!

If that doesn't work maybe a new circulator pump.

Ayuh,... Those usually last til the water pukes out the nose of it....

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

OK did the Don Test and heres what i came up with.

80 deg-580 ohms
90 deg- 530 ohms
100 deg-460 ohms
120 deg- 310 ohms
125 deg-270 ohms
140 deg-210 ohms
150 deg-165 ohms
160 deg-138 ohms
170 deg- 115 ohms
175 deg-100 ohms
190 deg 80 ohms
200 deg-70 ohms
210 deg 60 ohms

new sender??

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

OK i was looking at my engine and there is another sender of some type on the oppisite side of the thermostat housing and it has 2 wires and a clip like this one...

http://www.iboats.com/Temperature-S...7954718--**********.315913130--view_id.172068

what is this one for? Temp alarm?

The sender i will need is a 97257A1 right?? Is there a sierra part number for that sender?

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

...

 

[clerihew82]

Re: 1998 5.7 merc temp issue. Please Help!

Fixed. New temp sender.