Temperature Gauge

[FFCole411]

Does anyone know what would be causing my temperature to drop down to stone cold when I run 20MPH-25MPH or faster? When I am at idle or go around 5-10MPH my needle on the tempeature gauge goes up to half way on the gauge. I do not have a temperature reading so I do not know the exact temperature. As I said before, when I go 20MPH-25MPH or faster, the needle drops back down to stone cold, then back up when I slow down (the engine is not overheating). I have put in a new t-stat and even checked it in boiling water to make sure it works properly. I have also put in a new temp. sensor. I have no idea what could be causing this. Any help would be greatly appreciated.

The engine is a 2000 Volvo Penta V8 305 5.0L GXI

Thanks,

Cole

Edited April 12, 2009 by FFCole411

[electricjohn]

What is the temp of the water you are operating in?

[FFCole411]

Its roughly 54 degrees

[JUST-IN-TIME]

what drive do you have?

[FFCole411]

Its a Volvo Penta SX

[JUST-IN-TIME]

ok

here is a factory overheat guide from volvo

http://www.4shared.com/file/87557735/1c4a3..._Diagnosis.html

[electricjohn]

Are you the original owner of the boat? If not, it sounds to me like someone replaced a temperature sender with a temperature switch. The switch would be used if you had an idiot light instead of a gauge. Did you just replace what was in there? Or did you research for the proper part #?

[FFCole411]

I went down to my local boat mechanic and he was the one who looked up the temp. sensor and gave me the part. I am not the original boat owner. Wish I was then I would know what was done to the boat.

Yesterday I went and bought a new temp. gauge. This one has the actual readings unlike my other one on the dash that just says cold and hot. I started my boat up last night and let it run for roughly 20mins. The temp. gauge got up to about 200 degrees. My t stat is rated for 160 degrees. Does anyone know what might cause the temp. to get so high? I would think with a t stat rated for 160 degrees it should stay right around that. I was in my driveway with the muffs on and was at an idle.

Thanks,

Cole

Edited April 17, 2009 by FFCole411

[FFCole411]

Went out today. The new temp. gauge got up to a little over 200degrees when idling, roughly 205 degrees. I shut it down and let it cool down a little.

When I gave it WOT the temp. gauge would drop down to roughly 155-160 degrees.

Also when I would put it in neutral and rev it up, the temp. would drop down.

Any ideas anyone?

Thanks,

Cole

[XTI04]

I'm thinking water pump

[JUST-IN-TIME]

water pump

collapses exhaust hoses

collapse risers

water pick up blockage

read the link i posted bro, it tells you what to look for my friend

I always use a infa-red temp gun also to make sure my gauge in the boat is correct

[FFCole411]

Thanks for the link. I will make a copy and give it to my mechanic. I am not mechanically inclined enough to do that myself.

Thanks again,

Cole

[JUST-IN-TIME]

he should have access to this if he is a Volvo dealer