Water Pick Up/Raw Water Pump Question

[TyeeMan]

Hi All,

I have a 95 Lund Tyee 1850, with a 4.3 Volvo GS and DP-C drive and closed cooling system. So I've owned this boat on what will now be the 3rd season, so I'm still learning things about the Volvo set up and seeing things I've never seen before.
Last year I got the boat out, put the hose on it and it fired right up. This year I put the hose on it, (water on wide open) fired it up and after about a minute I smelled something hot so I shut her down. The belt driven raw water pump was so hot I couldn't touch it! Ok, so I likely just smoked the water pump impeller.
When I got out of the boat to make sure the muffs were still on the drive, they were, I noticed a stream of water coming out of a hole maybe about 1/2" diameter. This hole is in the front of the gear case, below the "cone". Maybe on the same plain as the gear oil drain plug.
Questions:
1. is this hole I'm referring to a drain hole, or some type of low water pick up? Is it supposed to be there?

2. The raw water pump is a Sherwood brand. I'm obviously going to replace the impeller, but there is a thing called the impeller cam. It has some grooving on it, are these grooves "normal" or should the cam be flat accross with no grooves. Having never seen one before I would call it accessive, but then I don't know. Should I replace the impeller cam?

Thanks in advance for your replys.

 

[Don S]

Re: Water Pick Up/Raw Water Pump Question

1. is this hole I'm referring to a drain hole, or some type of low water pick up? Is it supposed to be there?

It's called a secondary water pickup. When running on muffs, I usually just plug it. On my set of muffs I have wire with the tip off of one of the small sillycone tubes that fits tight and stays there.

2. The raw water pump is a Sherwood brand. I'm obviously going to replace the impeller, but there is a thing called the impeller cam. It has some grooving on it, are these grooves "normal" or should the cam be flat accross with no grooves. Having never seen one before I would call it accessive, but then I don't know. Should I replace the impeller cam?

The grooves are normal, that is the opening for the water to get forced into the cooling system and creates suction to draw water from the drive.

 

[TyeeMan]

Re: Water Pick Up/Raw Water Pump Question

Whew, thanks Don!! Having never seen the secondary water pick up I thought maybe some kind of plug came out. For fact I don't remember seeing that stream of water the previouse year so I wonder if it wasn't previously plugged. Believe me, the PO did some real bone head stuff.

So by not plugging the secondary water pick up, could that have taken out the pump impeller by not getting enough water to the impeller?

I don't know when the last time the impeller was changed, certainly not in the last 2-3 years so maybe it could have taken a set over winter and couldn't draw enogh vacuum to pull water up to the pump.

 

[Don S]

Re: Water Pick Up/Raw Water Pump Question

So by not plugging the secondary water pick up, could that have taken out the pump impeller by not getting enough water to the impeller?

Yes, when the impellers are getting weak and bent over and the vanes won't straighten, that slight lack of water volume can keep the water from not flowing.

Every other year is when you should be changing those impellers.

Be careful of those ujoint bellows too. every other year for them as well. They are thin, and if you pull the upper gear box during winterization so you can grease the ujoints, it takes about 10 extra minutes to replace the bellows. MUCH easier than anything Mercruiser ever did. If you have any previous Merc experience.

 

[TyeeMan]

Re: Water Pick Up/Raw Water Pump Question

Yeah the vanes were a bit bent over. Seemed a little weak too.

Yep my previouse boat had a Merc Alpha One witha 3 liter. LOTS more to do on the Mercs than with this Volvo. So far I love it!

Thanks again Don, you've helped me out a great deal since getting this rig witht the Volvo engine and drive.

 

[Scott Danforth]

Re: Water Pick Up/Raw Water Pump Question

I suggest pulling the impeller every winter and using it as the spare the following season when you install a new one. this keeps the vanes from taking a set over the winter. a new impeller every season is the best $22 you can spend for peace of mind.