Raw water only works when pressure applied

[Captain Fluegel]

I have read every thread I could find and could not find the answer, so here goes. I have a 99 Volvo Penta 4.3 GL with SX drive. When I ran the motor it heated to about 150 before I got nervous and applied pressure to the muffs to help force water through, When I did it started coming out at the plate and cooled the motor down to 130. Figuring that I probably got nervous I let it run to 175 before I forced the muffs again and this time it expelled water for a much longer period of time, maybe three to four minutes. The water had a lot of steam or exhaust(maybe both). The motor cooled down to about 140 this time and I let it run until 200 before forcing pressure on the muffs to cool down the motor. I have flushed in line and water comes out the bottom, I pull off the inlet and force the muffs and water comes through. I put the water hose on the hose that carries the water from the raw water pump to the thermostat housing, and every thing works perfect. I would think air was getting in except that once pressure is applied it seems to work fine, just like it needs a head start. What on earth could be causing this???

 

[bruceb58]

Re: Raw water only works when pressure applied

When was last time you changed your impeller?

 

[Maclin]

Re: Raw water only works when pressure applied

When in the lake the water level is much higher up on the drive, in effect pressurizing the inlet, and it is easier for the impeller to draw.

I am a little confused about the exact meaning when you say you have to apply pressure to the muffs. Do you mean turn the water up at the faucet? Or help the muffs seal around the drive? If it is the latter, then this may just be an issue with the style or brand of muffs in use.

 

[Captain Fluegel]

Re: Raw water only works when pressure applied

Impeller is brand new. Pulled it of and checked again, still good.
As far as the pressure I do mean the latter, I have to squeeze the muffs to the out drive. Surely the pressureadd from the depth of the water is less than that of the water hose, I guess what's frustrating me the most is that I can make it work, but it won't work on it's own.

 

[bruceb58]

Re: Raw water only works when pressure applied

So, have you had a problem when you run it in the water?

My muffs that I use supply water to each side of the drive. Not just one side. What are yours like? Maybe its just the muffs you are using.

I have one of these:
http://www.amazon.com/Moeller-Flush...&qid=1375767977&sr=8-4&keywords=volvo+flusher

 

[Captain Fluegel]

Re: Raw water only works when pressure applied

Ok, so I took everything apart again, found I had a piece of old impeller. Put it back together found a small leak from the housing of the raw water pump, hooked the muffs back up and it worked great for about ten minutes, then it quit taking in water. Not sure what to do with this any more.

 

[Whidbey]

Re: Raw water only works when pressure applied

Mine doesn't work well w/ out squeezing the muffs also. Definitely listen to these guys, they've been there. Like Maclin suggests, my drive works fine in the water. I got a horse trough and lower the trailer down so the drive is submerged just above the exhaust...works well for me. My muffs only load on one side though, so maybe better ones would help. Just thought I'd share. Don't let your motor get too hot.

 

[Captain Fluegel]

Re: Raw water only works when pressure applied

Ok, does it work temporarily when you squeeze or constantly?

 

[dypcdiver]

Re: Raw water only works when pressure applied

"found a small leak from the housing of the raw water pump" OK so what have you done about the small leak?
Even a very small leak will suck air and the prime will be lost. 3 places the pump can get air from 1. The seal on the crank 2. The "O" ring that seals the impeller housing to the back housing that carries the bearing and the seal 3. The plastic pipes where they are fixed into the brass body of the pump. You need to find and fix the leak.

 

[Maclin]

Re: Raw water only works when pressure applied

Like Whidbey, I use a large tub that I can get the drive down into and water level above the exhaust. It is not quite as high a level as in the lake but close, and if the plumbing from the drive inlets thru the drive and on up to the raw water pump is intact then the water will draw up nicely. If you do this it is important to keep a supply of water coming into the tub to keep from heating and re-heating the spent raw water. It is messy but about the same as leaky muffs that need the water pressure higher to keep up with the engine's draw. Draining the tub is always fun

 

[Captain Fluegel]

Re: Raw water only works when pressure applied

Too often these threads end without closure, so here is the update. I took my boat to Recency Marine here in Dallas. Told them the issue I was having. I was told that Volvos are notorious for sucking old impeller bits. He told me the was a port in the thermostat housing that often held small bits that prevented the thermostat from operating the way it was designed too. Applying pressure at the muffs forced open the thermostat allowing it to work for brief periods. He was going to do all the work to confirm this and I should have it back on Monday.

 

[dypcdiver]

Re: Raw water only works when pressure applied

So how did it go?

 

[Captain Fluegel]

Re: Raw water only works when pressure applied

Oddly. I got a call Monday to tell me the boat was fixed. I requested only a diagnostic on why it was over heating. Si this should have cost me fifty bucks but it's now going to cost me considerably more. Not sure how to handle this part of it.
As far as the cause of my Over heating it was a piece of impeller that had made it to the housing and lodged in the thermostat.