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alpine740
07-18-2007, 10:31 PM
At what temperature is the boat supposed to go into limp home mode? My '98 with LT1 got up to 240 degrees last weekend and never went into limp home mode, check engine light never came on either. Boat doesn't appear to have an audible alarm like my older boat had. Shouldn't both have occurred at this temperature? Any thoughts appreciated.

Monte
07-18-2007, 10:50 PM
At what temperature is the boat supposed to go into limp home mode? My '98 with LT1 got up to 240 degrees last weekend and never went into limp home mode, check engine light never came on either. Boat doesn't appear to have an audible alarm like my older boat had. Shouldn't both have occurred at this temperature? Any thoughts appreciated.

Dayum that is HOT....... Make sure to check everything... I would think it would have an alarm..

JimN
07-18-2007, 11:46 PM
I'm going to post this for the hard of learning- LIMP HOME MODE IS FOR CARS ONLY!!!!!!!!!!!!!!! Cars have a radiator, boats don't. There's no guarantee that cooling water will be going through the raw water pump and motor, so if a boat overheats, shut it the he!! off!

240 is way high and if you thought you could limp it home, this could be a very expensive lesson for you. LT-1 heads are about $1500 each and they really hate to be overheated.

I would like to bust out a can of whoopazz on the idiot who A) first called it "limp home mode" and B) told boaters about it. If it runs that bad, shut it off. A motor is only to be run in RPM reduction (the proper term) if there's imminent danger for the occupants. The boat doesn't count if the occupants are in danger- if they need to get out of Dodge, run it but if there's no threat, shut it off.

alpine740
07-18-2007, 11:56 PM
Boat was shut off as soon as my ski partner realized it was overheating. We swam it back to the dock. I had just got in the water and gone for a short ride at wakesurfing speed (4-5 minutes).
Boat never exhibited any signs of overheating other than the temp gauge; ran fine after I let it cool down. Hopefully I dont have a cracked head or bad head gasket now; really concerned about the aluminum heads. I am hoping that the short duration will not result in serious problems.

JimN
07-19-2007, 12:18 AM
Check the oil cooler for weeds and twigs and make sure the raw water hoses are tight and sealing well. If you're idling along and the temperature climbs, put it in neutral and rev it to about 2000 RPM. If everything is clear, the temperature should go back to normal.

How old is your impeller? If it's from last year, replace it.

alpine740
07-19-2007, 12:34 AM
Impeller is good. The trans cooler plugged up with debris from recent heavy rains. After I cleaned the cooler it ran at the normal temp. I am putting a strainer on to prevent it from happening again. I am just surprised that with all the electronics, the engine doesn't protect itself or give any sign of trouble / warning.

JimN
07-19-2007, 08:54 AM
If you can go to a MC dealer and connect it to a diagnostic computer (Tech 1 with the marine card or what the MC dealers are using now), check for overheats. There's a separate temperature sensor that informs the ECM and if this didn't see overheat, it won't go into RPM reduction. What you saw was from the one wire sender and while you don't want to see that, it may not have done much, if any, damage. A scan tool will not show overheats, just codes. If the impeller ran dry for more than about a minute, I would replace it and maybe keep the other one as a spare.

Has the water circulating pump been replaced recently?