Two Questions About A Mercruiser Raw Water Pump

[San_Diego_SeaRay]

Hello. Working w. a 1993 Bravo 7.4 engine (SN: 0F009622). From what I understand this engine originally came with a two piece seawater pump. But mine seems to be a one piece pump...so I guess this one isn't the original one.

Anyway, I've been trying to get this boat started after 6 months of not starting. Finally getting it to start reliably, but it keeps overheating. No water coming into the T stat housing, nor any coming into the oil/power steering cooler. So I checked the impeller. It's toast. All the pieces seem to be stuck in the sea water pump housing. So I remove all of the old impeller and buy a new one. With the housing facing me, I twist it in clockwise, same direction as the engine when you're facing the pulleys (so pulleys moving clockwise). I start her up again. No water at the Tstat again. Shut her down. Button her up as I've run out of time. Then back home I check the pictures I took and realize that the INTAKE hose had a T connection for another hose.

My questions are:

1. If this other hose is not capped or put in water, then the sea water pump is going to be sucking in air and can't suck in water, right? (picture shows intake hose w. the T connection
2. Did I put the impeller in the right direction? Clockwise?

 

[Bt Doctur]

As far as impeller direction ,it depends on what direction the pump spins being a serpentine belt. there also is a inlet/outlet that is reversable depending on the direction. That added hose most likely has a garden hose fitting that must be capped or the pump sucks air.
You may want to look into using an electric fuel pump, that fuel pump/raw water pump assembly is expensive

 

[San_Diego_SeaRay]

As far as impeller direction ,it depends on what direction the pump spins being a serpentine belt. there also is a inlet/outlet that is reversable depending on the direction. That added hose most likely has a garden hose fitting that must be capped or the pump sucks air.
You may want to look into using an electric fuel pump, that fuel pump/raw water pump assembly is expensive

Thanks Ed. Actually this is not a serpentine configuration; just various belts independent of each other, and they all turn clockwise. I see what you're saying if it was seprpentine though.

You're exactly right. I do recall a garden hose nipple at the end. I will plug it next time. Hopefully, that's the issue here.

If the fuel/water pump is working, are you saying replace it anyway? If so, what would replace the sea water pump?

 

[alldodge]

The pumps are expensive IF they are replaced as a whole unit. They are no more expensive to overhaul, cost about $50 to do. Note the two plugs on the side of the pump. Pull the top plug and nothing should come out except maybe a drop of two of gear lube. If it come pouring out then the fuel pump is leaking gas into the housing. The bottom one drains the unit, the top is filled to the top.

If a lot comes out you probably need to replace the fuel pump. If nothing comes out, pull the bottom and drain, then refill

BTW you might want to check the impeller again because it may have burned up again due to sucking air

 

[Bt Doctur]

If your going to use that type of flushing system install a ball valve inline.this will eliminate the possability of the cap leaking air

 

[San_Diego_SeaRay]

Ok great. Thanks to both of you for your help. I should be able to address these questions on Wednesday and, fingers crossed, I'll get this problem licked.

 

[HT32BSX115]

Ok great. Thanks to both of you for your help. I should be able to address these questions on Wednesday and, fingers crossed, I'll get this problem licked.

Howdy,

You likely have another problem that you'll need to address. That raw water impeller if it did disintegrate (and any previous disintegrations) will have resulted in pump debris going downstream to the oil cooler (over on the other side of the engine) . The oil cooler has raw water passages small enough to prevent the pieces from getting to the t-stat, but it can plug it up bad enough that back-flushing will not dislodge the pieces.

My oil cooler was so badly clogged that I had to use needle-nose pliers to pluck the pieces out of the raw-water input end. Here's a depiction of the raw water cooling circuit of your engine if it's stock.

You'll probably need to remove the cooler to clean it out.

Cheers,

Rick