View Full Version : LT1 Water Pump replacement

05-13-2012, 08:42 PM
I have a 1999 MariStar 230VRS with the LT1 Corvette motor. Upon hooking everything up after getting my boat out of winter storage, I hooked up my water source, turned the key, and that mighty LT1 roared to life. I was beaming with pride! I listened to her purr for a moment, and then thought I had better check for leaks. I went to the starboard side first and all looked good. I then proceeded to the port side, only to my disbelief to see water spraying all over the place. After climbing inside the engine compartment, I could see that the water was comming out of the weep hole on the bottom of the water pump, dropping on the alternator belt, and flinging all over the place! I quickly shut her down, removed it, and found the bearings were shot. I began a long frustrating internet search for a replacement. I ordered the new water pump (along with both thermostats and gaskets- since all were original ). When everything came in, I sprayed the pump with Black high heat engine enamel to match the old one. This week I'm going to attempt to install the new pump. It look like a pretty straightforward job, but I was looking for any hints, or suggestions from you guys before staring the project. I want this to go smoothly because I can't wait to get out on the water after the long winter break!!!

Table Rocker
05-13-2012, 10:12 PM
It's pretty straight forward. If your boat is set up anything like mine, you will need to remove the mixing thermostat housing and mount. Since your boat is a '99, your steam pipes should already be at the front of the engine so you won't need to move them.

You might check and make sure you don't have an oil leak around the shaft from the cam that drives the water pump. From what I understand, that is the most common location for LT1 oil leaks. Mine was leaking there. If you need a seal, it seems to only be available as part of the timing cover set available at your local parts store. I think it was less than $10 for the kit.

Take your time and scrape all the old gaskets off the block. Put your new pump on. There are alignment dowels to hold the pump in place. You will need to put some sealant on the threads of the lowest bolt on each side, they go through into the cooling passages and can leak if not sealed. Crank the bolts down to 30 ft.- lbs. and put it all back together. Fire it up and get to the lake!

Where did you buy your pump and which model did you get? Does your boat have a heater? There are modifications to improve heater performance discussed in other threads.

05-13-2012, 10:47 PM
After taking off the old one make sure to save the little drive shaft piece that goes between the pump and the cam on the engine. I did mine at the dock, handed the old pump to my brother and the little drive shaft fell off, headed for the water. Luckily he caught it.