No water coming into starboard engine.......

R

rgl1100

Member
Jun 21, 2010
146
Massachusetts
Boat Info
340 Sundancer 2003
Engines
Twin Merc 8.1S
Launched the boat today.......Port engine turned on fine with water coming out of exhaust, no problems. Starboard engine turned over fine. Sounds fine but no water. You might say, "must need an impeller", right..........I changed the impeller on the engine a week ago and tested out of the water and it was perfect. The guy before me who owned the boat had valves placed on the strainer. With the seacock open I slightly opened the strainer valve on the starboard engine and nothing came out?! I opened it fully and still nothing. The seacock is in the open position.....how can this be??? The only explanation I can think of is that there is a blockage of the water at the seacock. Am I thinking about this correctly? If I opened the valve to the strainer and the seacock is open wouldn't water come through that strainer valve with a vengence??? I've included a pic of the strainer and valve just to show. I only had a moment today so I closed off the strainer and will go down tomorrow. I need to close off the seacock and open up the strainer to see if something is amiss. I'm baffled that something could clog the seacock to that extent.
 
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For some reason I can't seem to upload the image of the strainer.............you've all seen them. It's the typical strainer with a 90 degree throw valve attached to the top. I assume the previous owner would use them to flush the engines with fresh water while in the ocean. I'll keep trying but anythoughts would be appreciated. Could something have happened to the impeller. The engine worked fine with a hose placed in the strainer..............
 
somewhere between thru hull and strainer you hve a blockage. plastic ice bags can be a killer.
 
I have been told by merc mechanics that running a hose up into the thru hull with a hose is not a good ideA sicw the water is airated and not able to supply enough gpm and will cause cavitation in the impeller housing not cooling the impeller enough or lubricating it enough. They have seen vanes snap off after a few minutes of running its not like using muffs on io. But you could have a blockage but unlikely if you havent run and you ran a hose through seacock. If you crack the strainer and crack the ball valve open you should get water to the strainer.
 
I had a similar issue with 496 8.1s on both my BAJA 30 Outlaw (sold) and my Sea Ray 330DA. Odd, but the Sea Ray started pumping water once the engines where rev'd a few times. The BAJA however, required draining the water out of the sea water pump over and over (about a 1/2 hour). It seems it was vapor or air locked. We opened and closed the drain valves and finally it started pumping water and instantly the heat exchangers where cool (by the way the guy who bought my BAJA changed the impelers and said they looked good). The drains on my BAJA 496's are just to the left under the sea water pump. I believe this is how they drain the water to winterize the boat (not 100% sure because I have it done).
 
may sound stupid ...but could you have reversed the rotation of the vanes on the impeller on installing ??
 
I had a similar problem. I had both my impellers changed in January by an authorized Merc dealer whom I have known, used, and trusted for over 20 years. They ran like a top on the initial run home of about two hours. Sat at the dock overnight. Next day the port engine wouldn't pump and quickly overheated. Called my mechanic and he said to try this before he would come out.
1) Let it cool overnight. 2) Upon initial start up, immediately take it up to about 1,500 rpms for 30-60 seconds and see what happens. Sure enough it started pumping and has always been fine since! Supposedly the new impeller doesn't "mate" up to the old housing and doesn't pump properly at first???? Sounds iffy but it did work for me. I guess the additional rpms increase suction enough to get it flowing. Worth a try..... good luck.
 
Rgl1100
i experienced a similar problem that u r seeing. I replaced both impellers before launch. Both motors pumped fine on the hard. I launched and both motors were pumping water. The starboard took a little longer to pump on initial launch. We idled out to a mooring as it was a cold, rainy day. Next day no water pumping out of starboard motor upon startup. I pulled the pump to check the impeller, looked brand new just as when I installed it. Glad it was the starboard side, i had the pump out, checked impeller and back in 45 mins. i reinstalled the pump and started motor and what do you know, water began to pump. I believe there was an airlock or vapor lock. I have been out since then and all has been fine. I would suggest with the engine off, close the sea cock , fill the strainer with a hose and open the bottom drain on the sea water pump. See if you get water flow. I would bet you have an airlock.
 
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I went out today to check the problem and checked all the connections. Took off several hoses. No blockage. Checked sea strainer, impeller. No problem. I started up the boat again and revved the engine a bit and, what do you know........., water coming out. Now, to be honest, I might have been pumping all along and it just took a bit to fill up the mufflers prior to seeing water out of the hose. I didn't let the engine go very long before shutting it down. I've been told by several mechanics that even a small amount of time running without cooling can scorch the walls of the cylinders and/or bend valves..................regarless, seems to work perfect. I'm not going to question the searay G-ds on this one................
 
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