Anonymous
01-21-2003, 11:32 PM
Earl
normal member in standard member. 1. Coolant Temperature
I have a '97 246 Open with the PMC 350 chevy & FWC. Under way the engine temp only registers 120 - 140 F & the book says 170 - 210 is normal. How can I check this out without pulling the thermostat?
Date: 12:28 p.m. on 02-13-2001
Leprechaun
premium member in standard member. 2. Re:Coolant Temperature
Earl - 2 points here. First, you just might be one of the lucky ones who got a high-flow Heat Exchanger with the bigger tubes. Experience on my dock (With the bunch of Shamrocks I dock with) is that the H.E.s that PCM puts on these engines as original equipment are a little restrictive, having small internal tubes. There exists out there larger-tubed H.E.s that keep the temp down in the range you describe. My buddy got them from Basic Power Industries in Harker's Island, N.C. and they do an excellent job of keeping temps down. BUT - that's on carbed engines. If you have Fuel Injection, these low temps could concievably trick the ECM into thinking the engine is still warming up and this will possibly result in the computer supplying an over-rich mixture to the cylinders. Not Good. But only if you have F.I., if not then Happy Day, you got a good one. If you have F.I. - I think a discussion with either your dealer or perhaps direct with PCM might be in order.
Now all the above of course assumes that your oil pressure sending unit and gauge are working properly. If not, then not. Let me give you an example. I belong to an antique Corvette Owner's club. One of my good friends owns a very gorgeous 27K-mile all-original 1969 L89 427/435hp tri-powered car - original down to the lug-nuts and certified by several Corvette Societys to be at the very top of the corvette world - easily a $75K car. Now he's a real fuss-pot about maintenance and every little creak and groin of this 30-year old never-needed-rebuilding car gets analyzed and fixed almost before it occurs. He recently found his oil pressure dropping to around 2 pounds at idle and immediately ordered up a set of main bearings for it. Up on jack stands she went and several curse-filled nights of lousey lower-engine work later he was done. He turned the key, and Voila - still 2 pounds of pressure. He just couldn't/wouldn't take my original advice to grab an oil pressure gauge off his Snap-on truck and double-check the pressure at the pump outlet. Well, all the car need was a new sending unit and it was fine. 35 pounds at idle and 50 pounds on the road. Moral of the story - you can't always trust your gauges. Try this - go to an auto parts store and pick up a Radiator thermometer (The one with the Large head, not the tiny headed one that always drops into the radiator). Take the cap off the expansion tank and start her up. Get her good and hot, and with the thermostat open (That's another thing - I don't think a thermostat will open at the low temps you quote . . . HMMMM, even more suspicious of the gauge now)plunge the thermometer into the now-hopefully overflowing coolant and see just exactly what the coolant temp is. I'll bet its around 160 at fast idle and around 175-180 after a good run. Try it and get back to us. Rgds, Leprechaun
Date: 06:27 p.m. on 02-13-2001
Prior Engagement
premium member in standard member. 3. Re:Coolant Temperature
I second Lep's analysis. Sounds like a faulty gauge or sending unit. Try the process of elimination before the process of replacement. Ouch, I bet Lep's friend was one pi$$@d off individual!
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 10:21 p.m. on 02-13-2001
Capt_Dog
normal member in standard member. 4. Re:Coolant Temperature
I have the 351 indmar 92 vintage and I averaged about 175~180 then my impeller self destructed. New impeller I get around 155~165. No during the winter months our water temps fluctuates down about 35 degress from summer and I can only get about 140~155 and it takes awhile before the thermo opens and registeres anything. All of this of course is judging by the OEM temp gauge and should be taken as relative measurements. My risers are less than 60 hours old.
--------------------------------------------------------------------------------
Thanks, Lee
Date: 08:10 a.m. on 02-14-2001
Leprechaun
premium member in standard member. 5. Re:Coolant Temperature
Earl - Re my earlier response - Second Paragraph first sentence should refer to your water temp sending unit and gauge, not your oil pressure setup, Geeesh, this gout medicine has me all screwed up. Leprechaun
Date: 05:16 p.m. on 02-14-2001
Earl
normal member in standard member. 6. Re:Coolant Temperature
Thanks to those who responded to my question! We measured the temp in the expansion tank after the thermostat opened and found ~140 F. at idle RPM's on the trailer. We will launch in a month or so and re-measure before pulling the thermostat. The dash indicator was off about 20 degrees.
Leprechaun
premium member in standard member. 7. Re:Coolant Temperature
Bingo. Leprechaun
Date: 12:07 p.m. on 02-15-2001
IrishWake
8. Re:Re:Coolant Temperature
Lep, when you say put the thermometer in the expansion tank, do you mean the tank that has the radiator cap on it or do you mean the overflow tank?
Regards
Randy
Date: 12:45 p.m. on 02-15-2001
Earl
normal member in standard member. 9. Re:Re:Re:Coolant Temperature
My system has only the tank with the radiator cap. There is no expansion tank.
Leprechaun
premium member in standard member. 10. Re:Coolant Temperature
Randy - The expansion tank is the metal one atop the engine with the Radiator Cap on it. That's where the thermometer goes. The other tank is an aftermarket overflow catch tank. It catches and saves the coolant that makes it past the Expansion tank. The alternative is for the coolant to go into the bilge. N/G. - My rig didn't have the plastic overflow tank when I bought it. I added one from a Mercruiser V/8 configuration.
Earl - for about $20 go to your local Mercruiser dealer and buy yourself an overflow tank and a piece of plastic hose. It will retain the extra coolant that makes its way past the radiator cap and will allow you to increase your total coolant capacity by around a quart. No down side to this upgrade. Rgds, Leprechaun
Date: 04:07 p.m. on 02-15-2001
Prior Engagement
premium member in standard member. 11. Re:Coolant Temperature
My PCM does not have an overflow tank. Does anyone know if there is one available? Overflow tank that is. Discharges to the bilge
Thanks in advance.
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 05:21 p.m. on 02-15-2001
IrishWake
12. Re:Re:Coolant Temperature
--------------------------------------------------------------------------------
Leprechaun (02-15-2001 04:07 p.m.):
Randy - The expansion tank is the metal one atop the engine with the Radiator Cap on it. That's where the thermometer goes. The other tank is an aftermarket overflow catch tank. It catches and saves the coolant that makes it past the Expansion tank. The alternative is for the coolant to go into the bilge. N/G. - My rig didn't have the plastic overflow tank when I bought it. I added one from a Mercruiser V/8 configuration.
Earl - for about $20 go to your local Mercruiser dealer and buy yourself an overflow tank and a piece of plastic hose. It will retain the extra coolant that makes its way past the radiator cap and will allow you to increase your total coolant capacity by around a quart. No down side to this upgrade. Rgds, Leprechaun
--------------------------------------------------------------------------------
Lep, Where did you mount the overflow tank?
Randy
Date: 05:27 p.m. on 02-15-2001
Leprechaun
premium member in standard member. 13. Re:Coolant Temperature
Randy - Why did I think you were gonna ask that? I was down to my boat tonite and said to myself "Randy will ask about the tank mounting location, wish I had a Digital Camera." O.K. - so the hose (Clear plastic - available at Home Depot) comes off the expansion tank, runs back along the inside edge of the Stbd side valve cover, down under the stbd exhaust hose (under the Batttery tray), thru the same bulkhead limber hole that the fuel line run thru (I think - have to check tommorrow) and then up thru the side of the fiberglass vertical stantion and thru a hole bored in the stbd side teak side tray (The rear-most piece of teak) then into the bottom of the overflow tank which is mounted to that same piece of teak. With this mounting being always exposed, you only have to glance downward to monitor the bright green fluid level - overheats or missing fluid is immediately and readily apparent. Again, wish I had a digital camera. Leprechaun
Date: 08:06 p.m. on 02-15-2001
Engineman
14. Re:Coolant Temperature
Earl,
After you check the sender and guage. Check the thermostat. We have had some engines that came through with the raw water stat instead of the fresh water stat. Also we have had no cause to change the heat exchanger unless it was coroded through. If it is just dirty take it to a radiator shop and have it flushed. $25 bucks is cheaper than $300 plus and you have more money for bait.
Date: 10:23 a.m. on 02-19-2001
Earl
normal member in standard member. 15. Re:Re:Coolant Temperature
I appreciate your response Engineman. We had suspected that the raw water thermostat may be installed in place of the FWC unit. There is no heat exchanger problem as of yet. Every thing runs too cool. I wonder if it is advisable to make the switch to the high temp unit? The raw water system is flushed with fresh water each trip once the boat is on the lift.
--------------------------------------------------------------------------------
Engineman (02-19-2001 10:23 a.m.):
Earl,
After you check the sender and guage. Check the thermostat. We have had some engines that came through with the raw water stat instead of the fresh water stat. Also we have had no cause to change the heat exchanger unless it was coroded through. If it is just dirty take it to a radiator shop and have it flushed. $25 bucks is cheaper than $300 plus and you have more money for bait.
--------------------------------------------------------------------------------
Date: 05:41 p.m. on 02-20-2001
Earl
normal member in standard member. 16. Re:Re:Coolant Temperature
I appreciate your response Engineman. We had suspected that the raw water thermostat may be installed in place of the FWC unit. There is no heat exchanger problem as of yet. Every thing runs too cool. I wonder if it is advisable to make the switch to the high temp unit? The raw water system is flushed with fresh water each trip once the boat is on the lift.
Date: 05:42 p.m. on 02-20-2001
normal member in standard member. 1. Coolant Temperature
I have a '97 246 Open with the PMC 350 chevy & FWC. Under way the engine temp only registers 120 - 140 F & the book says 170 - 210 is normal. How can I check this out without pulling the thermostat?
Date: 12:28 p.m. on 02-13-2001
Leprechaun
premium member in standard member. 2. Re:Coolant Temperature
Earl - 2 points here. First, you just might be one of the lucky ones who got a high-flow Heat Exchanger with the bigger tubes. Experience on my dock (With the bunch of Shamrocks I dock with) is that the H.E.s that PCM puts on these engines as original equipment are a little restrictive, having small internal tubes. There exists out there larger-tubed H.E.s that keep the temp down in the range you describe. My buddy got them from Basic Power Industries in Harker's Island, N.C. and they do an excellent job of keeping temps down. BUT - that's on carbed engines. If you have Fuel Injection, these low temps could concievably trick the ECM into thinking the engine is still warming up and this will possibly result in the computer supplying an over-rich mixture to the cylinders. Not Good. But only if you have F.I., if not then Happy Day, you got a good one. If you have F.I. - I think a discussion with either your dealer or perhaps direct with PCM might be in order.
Now all the above of course assumes that your oil pressure sending unit and gauge are working properly. If not, then not. Let me give you an example. I belong to an antique Corvette Owner's club. One of my good friends owns a very gorgeous 27K-mile all-original 1969 L89 427/435hp tri-powered car - original down to the lug-nuts and certified by several Corvette Societys to be at the very top of the corvette world - easily a $75K car. Now he's a real fuss-pot about maintenance and every little creak and groin of this 30-year old never-needed-rebuilding car gets analyzed and fixed almost before it occurs. He recently found his oil pressure dropping to around 2 pounds at idle and immediately ordered up a set of main bearings for it. Up on jack stands she went and several curse-filled nights of lousey lower-engine work later he was done. He turned the key, and Voila - still 2 pounds of pressure. He just couldn't/wouldn't take my original advice to grab an oil pressure gauge off his Snap-on truck and double-check the pressure at the pump outlet. Well, all the car need was a new sending unit and it was fine. 35 pounds at idle and 50 pounds on the road. Moral of the story - you can't always trust your gauges. Try this - go to an auto parts store and pick up a Radiator thermometer (The one with the Large head, not the tiny headed one that always drops into the radiator). Take the cap off the expansion tank and start her up. Get her good and hot, and with the thermostat open (That's another thing - I don't think a thermostat will open at the low temps you quote . . . HMMMM, even more suspicious of the gauge now)plunge the thermometer into the now-hopefully overflowing coolant and see just exactly what the coolant temp is. I'll bet its around 160 at fast idle and around 175-180 after a good run. Try it and get back to us. Rgds, Leprechaun
Date: 06:27 p.m. on 02-13-2001
Prior Engagement
premium member in standard member. 3. Re:Coolant Temperature
I second Lep's analysis. Sounds like a faulty gauge or sending unit. Try the process of elimination before the process of replacement. Ouch, I bet Lep's friend was one pi$$@d off individual!
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 10:21 p.m. on 02-13-2001
Capt_Dog
normal member in standard member. 4. Re:Coolant Temperature
I have the 351 indmar 92 vintage and I averaged about 175~180 then my impeller self destructed. New impeller I get around 155~165. No during the winter months our water temps fluctuates down about 35 degress from summer and I can only get about 140~155 and it takes awhile before the thermo opens and registeres anything. All of this of course is judging by the OEM temp gauge and should be taken as relative measurements. My risers are less than 60 hours old.
--------------------------------------------------------------------------------
Thanks, Lee
Date: 08:10 a.m. on 02-14-2001
Leprechaun
premium member in standard member. 5. Re:Coolant Temperature
Earl - Re my earlier response - Second Paragraph first sentence should refer to your water temp sending unit and gauge, not your oil pressure setup, Geeesh, this gout medicine has me all screwed up. Leprechaun
Date: 05:16 p.m. on 02-14-2001
Earl
normal member in standard member. 6. Re:Coolant Temperature
Thanks to those who responded to my question! We measured the temp in the expansion tank after the thermostat opened and found ~140 F. at idle RPM's on the trailer. We will launch in a month or so and re-measure before pulling the thermostat. The dash indicator was off about 20 degrees.
Leprechaun
premium member in standard member. 7. Re:Coolant Temperature
Bingo. Leprechaun
Date: 12:07 p.m. on 02-15-2001
IrishWake
8. Re:Re:Coolant Temperature
Lep, when you say put the thermometer in the expansion tank, do you mean the tank that has the radiator cap on it or do you mean the overflow tank?
Regards
Randy
Date: 12:45 p.m. on 02-15-2001
Earl
normal member in standard member. 9. Re:Re:Re:Coolant Temperature
My system has only the tank with the radiator cap. There is no expansion tank.
Leprechaun
premium member in standard member. 10. Re:Coolant Temperature
Randy - The expansion tank is the metal one atop the engine with the Radiator Cap on it. That's where the thermometer goes. The other tank is an aftermarket overflow catch tank. It catches and saves the coolant that makes it past the Expansion tank. The alternative is for the coolant to go into the bilge. N/G. - My rig didn't have the plastic overflow tank when I bought it. I added one from a Mercruiser V/8 configuration.
Earl - for about $20 go to your local Mercruiser dealer and buy yourself an overflow tank and a piece of plastic hose. It will retain the extra coolant that makes its way past the radiator cap and will allow you to increase your total coolant capacity by around a quart. No down side to this upgrade. Rgds, Leprechaun
Date: 04:07 p.m. on 02-15-2001
Prior Engagement
premium member in standard member. 11. Re:Coolant Temperature
My PCM does not have an overflow tank. Does anyone know if there is one available? Overflow tank that is. Discharges to the bilge
Thanks in advance.
--------------------------------------------------------------------------------
Fair seas and tight lines,
Mike N.
Date: 05:21 p.m. on 02-15-2001
IrishWake
12. Re:Re:Coolant Temperature
--------------------------------------------------------------------------------
Leprechaun (02-15-2001 04:07 p.m.):
Randy - The expansion tank is the metal one atop the engine with the Radiator Cap on it. That's where the thermometer goes. The other tank is an aftermarket overflow catch tank. It catches and saves the coolant that makes it past the Expansion tank. The alternative is for the coolant to go into the bilge. N/G. - My rig didn't have the plastic overflow tank when I bought it. I added one from a Mercruiser V/8 configuration.
Earl - for about $20 go to your local Mercruiser dealer and buy yourself an overflow tank and a piece of plastic hose. It will retain the extra coolant that makes its way past the radiator cap and will allow you to increase your total coolant capacity by around a quart. No down side to this upgrade. Rgds, Leprechaun
--------------------------------------------------------------------------------
Lep, Where did you mount the overflow tank?
Randy
Date: 05:27 p.m. on 02-15-2001
Leprechaun
premium member in standard member. 13. Re:Coolant Temperature
Randy - Why did I think you were gonna ask that? I was down to my boat tonite and said to myself "Randy will ask about the tank mounting location, wish I had a Digital Camera." O.K. - so the hose (Clear plastic - available at Home Depot) comes off the expansion tank, runs back along the inside edge of the Stbd side valve cover, down under the stbd exhaust hose (under the Batttery tray), thru the same bulkhead limber hole that the fuel line run thru (I think - have to check tommorrow) and then up thru the side of the fiberglass vertical stantion and thru a hole bored in the stbd side teak side tray (The rear-most piece of teak) then into the bottom of the overflow tank which is mounted to that same piece of teak. With this mounting being always exposed, you only have to glance downward to monitor the bright green fluid level - overheats or missing fluid is immediately and readily apparent. Again, wish I had a digital camera. Leprechaun
Date: 08:06 p.m. on 02-15-2001
Engineman
14. Re:Coolant Temperature
Earl,
After you check the sender and guage. Check the thermostat. We have had some engines that came through with the raw water stat instead of the fresh water stat. Also we have had no cause to change the heat exchanger unless it was coroded through. If it is just dirty take it to a radiator shop and have it flushed. $25 bucks is cheaper than $300 plus and you have more money for bait.
Date: 10:23 a.m. on 02-19-2001
Earl
normal member in standard member. 15. Re:Re:Coolant Temperature
I appreciate your response Engineman. We had suspected that the raw water thermostat may be installed in place of the FWC unit. There is no heat exchanger problem as of yet. Every thing runs too cool. I wonder if it is advisable to make the switch to the high temp unit? The raw water system is flushed with fresh water each trip once the boat is on the lift.
--------------------------------------------------------------------------------
Engineman (02-19-2001 10:23 a.m.):
Earl,
After you check the sender and guage. Check the thermostat. We have had some engines that came through with the raw water stat instead of the fresh water stat. Also we have had no cause to change the heat exchanger unless it was coroded through. If it is just dirty take it to a radiator shop and have it flushed. $25 bucks is cheaper than $300 plus and you have more money for bait.
--------------------------------------------------------------------------------
Date: 05:41 p.m. on 02-20-2001
Earl
normal member in standard member. 16. Re:Re:Coolant Temperature
I appreciate your response Engineman. We had suspected that the raw water thermostat may be installed in place of the FWC unit. There is no heat exchanger problem as of yet. Every thing runs too cool. I wonder if it is advisable to make the switch to the high temp unit? The raw water system is flushed with fresh water each trip once the boat is on the lift.
Date: 05:42 p.m. on 02-20-2001