merc 260 raw water pump - does it matter which hose connects to which outlet?

bill91817

Cadet
Joined
Jan 23, 2017
Messages
25
not a great weekend
took the (new to me) boat out for its first run after replacing manifolds, and a few other things (including ball valve for through hull inlet). I also pulled the raw water pump to check it - the impellor was as new no cracks or wear and has grease around the wear plate (which as new). So I put the pump back and connected the hoses the way I thought they had gone - I might have got it wrong but I am sure I didn't and I am not sure that it matters? - well something has gone wrong....

I ran the engine (merc 5.7 carby) up on the trailer (hose connects to t-piece in raw water pipe before the raw water pump) -I noticed pretty quickly the water in the manifolds was boiling - shut it down and realised the through hull ball valve was open so some water was running back out the through hull instead of it all going to the raw water pump.
I shut the ball valve to the through hull inlet and re ran the engine on the water hose - ran fine, water coming the exhaust was warm to hot but it ran fine.
Shut it down -
Next day re opened ball valve and launched the boat to take for a run, idled out of the marina and a few minutes later as I took the boat up to about 2000 rpm noticed the temp rising fast - slowed down and the alarm came on - shut it down and opened engine cover - very hot and bit of smoke coming out .
Anchored and waited for her to cool down - pulled the hoses off the top of the engine - where the raw water comes in and goes to the circulating pump (pic below ) and started the engine - no water coming at all..... called for a tow :-(

So I am guessing I have damaged/destroyed the impellor - will try and pull the pump again this week and assuming it is that (cant really be anything else!) does it matter which hose is connected to which outlet? - the way he unit is set up (two inlets off the back of the pump like the one in the 2nd pic below) I would have thought it didn't matter?

thanks in advance
bill
 

Attachments

  • photo259520.jpg
    photo259520.jpg
    328.4 KB · Views: 0
  • photo259521.jpg
    photo259521.jpg
    17.4 KB · Views: 0
Last edited:

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Yes, it matters. One is an inlet, one is an outet. The pump is not bi-directional
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,092
Actually it is bi-directional (so to speak)depends on where the inlet hose is connected.That same pump is used on CR motors also just by reversing the inlet/outlet hoses
With the thru hull open theres a good chance you damaged the impeller
UntitledBA1_zps4yxch0j7.jpg
 
Last edited:
Top