is my water pump base correct

[jimbo2675]

Before I changed my water pump I had a strong stream of water from the tell.tale, but since I have changed it I now only have a trickle, I have since changed the thermostas and poppet valve but still only a trickle, I have removed the lower unit again to check pickup connection and seal , all Ok. .when I connect a hose pipe directly to the pick up tube I get a good stream of water from tell.tale so no blockage. Looking at the new pump base it has 2 grooves cut in it, one from the driveshaft hole, this is OK as the old base has this but it is drilled instead of groove, but the other groove is not on the old base, so I am wondering am I losing pressure from this other groove, the new base is the correct part number for the year of my motor, now as far as I can make out the base for later engines does not have this other groove , so is it possible that the later base gives more water pressure. Photos attached.

 

[Chris1956]

All water pressure is developed in the impeller cup. I have no idea if it is the right pump base. Do the holes in the base match the passage way of the water intakes in the gearcase? Does the wearplate match the pump base, in terms of the holes at the rear? Do the holes in the three gaskets match the holes in the pump base and wearplate? If not, the water will not be able to get into the pump. You do have the water tube guide tube installed in the pump outlet?

 

[minuteman62-64]

I've got a post on here somewhere about a similar experience I had. Turned out the new gasket was much thinner than the old one - result, the pump housing wasn't compressing the gasket against the base plate. Went to O'Reillys and got some gasket material with thickness closer to original. Cut my own gasket. Bingo, flow restored.

 

[jimbo2675]

All water pressure is developed in the impeller cup. I have no idea if it is the right pump base. Do the holes in the base match the passage way of the water intakes in the gearcase? Does the wearplate match the pump base, in terms of the holes at the rear? Do the holes in the three gaskets match the holes in the pump base and wearplate? If not, the water will not be able to get into the pump. You do have the water tube guide tube installed in the pump outlet?

Thanks for the reply, everything matches and I do have the water tube guide in the pump outlet.

 

[jimbo2675]

I've got a post on here somewhere about a similar experience I had. Turned out the new gasket was much thinner than the old one - result, the pump housing wasn't compressing the gasket against the base plate. Went to O'Reillys and got some gasket material with thickness closer to original. Cut my own gasket. Bingo, flow restored.

Thanks for the reply , now I come to think of it the pump base gasket did seem a bit thin for a new gasket, so I will remove again as soon as I get time and fit a thicker gasket and see if that sorts it and post the result.

 

[jimbo2675]

Thanks for the reply , now I come to think of it the pump base gasket did seem a bit thin for a new gasket, so I will remove again as soon as I get time and fit a thicker gasket and see if that sorts it and post the result.

OK, so I have removed the pump base again and the gasket does have compression marks on it, so that is not the problem, I forgot to say in my original post the engine is a mercury blackmax 150, 1983 according to serial no. 6222131 and the sierra pump part no. 18-3316 is the one I fitted and correct for that year according to I boats, so any more ideas as to what the problem could be, does any one know why it has the extra cut out in the base.

 

[Chris1956]

You are installing the drive key to make the impeller turn, right? I would be surprised if the new pump base is the issue. If the wearplate and gaskets match the water intakes, I would expect it to work. Pull the thermostats to allow the water to flow freely. The poppet valve should open as the water pressure builds to 10 PSI or so.

 

[jimbo2675]

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[jimbo2675]

You are installing the drive key to make the impeller turn, right? I would be surprised if the new pump base is the issue. If the wearplate and gaskets match the water intakes, I would expect it to work. Pull the thermostats to allow the water to flow freely. The poppet valve should open as the water pressure builds to 10 PSI or so.

Hi Chris 1956, yes the drive key is in and gaskets and wear plate match the water intake's, as I said in my original post I do get a flow from the tell tale but it is nowhere near as strong as it was before I changed the pump, it used to pee about 12inches horizontally on idle with the old pump, now it is about 2inches and intermittent, I've even tested the new stats and they open up fine.

 

[Chris1956]

It is hard to assess the function of the impeller by looking at the telltale. A lot of those motors do not have any telltale, until the motor warms and the thermostat opens. At idle on a flush device, with cold water, you may never get a telltale. Can you put a water pressure gauge on her? You should see up to 5 PSI at fast idle.

 

[minuteman62-64]

Just a thought - OEM or 3'd party impeller? I'm using Sierra impellers now and I've noticed they don't fit quite as tight in the pump housing as the OEM ones. Tell-tale flow a little less, but, no overheating issues.

 

[jimbo2675]

It is hard to assess the function of the impeller by looking at the telltale. A lot of those motors do not have any telltale, until the motor warms and the thermostat opens. At idle on a flush device, with cold water, you may never get a telltale. Can you put a water pressure gauge on her? You should see up to 5 PSI at fast idle.

Hi Chris, dug out my water pressure gauge but could not find a suitable adaptor to connect it up, so run engine and loosened stat housings and water pissing out, so must be pressure there, took the revs up to about 2000 and seems to be a good stream, but as soon as it idles again the stream stops for about 10 seconds and then returns to a trickle, as minuteman said could be this sierra impeller not as good as OE, Soon as I get a chance going to put it in the water and see what happens, and will post result.
,

 

[jimbo2675]

Just a thought - OEM or 3'd party impeller? I'm using Sierra impellers now and I've noticed they don't fit quite as tight in the pump housing as the OEM ones. Tell-tale flow a little less, but, no overheating issues.

Hi minuteman, yes it is a sierra pump, so could be that, as I said to Chris going to dip her in the water as soon as I get a chance and see what happens.

 

[Faztbullet]

It aint the impeller.......

 

[Chris1956]

I used a brass tee to connect the water pressure gauge to the water hose from the top of the motor to the bottom of the motor. That might be a good place for you to try.

 

[jimbo2675]

No Title

OK managed to get 1/2 inch adaptor to go in top of block and connect pressure gauge, see photo's and explanations.so looks like pump OK. I have tested thermostats by putting them in saucepan and heating up from cold and they open fine.

 

[jimbo2675]

Took the boat out today and no problem's, still only a trickle from telltale on idle even when engine warmed up, but once revs above 1200 flow is good and poppet opens at speed, still Dont understand why the flow from telltale is not as strong on idle as it was before I changed the pump but it does not seem to be an issue, going to fit a water pressure gauge on the dash just to be on the safe side. Thanks to everyone's advice on this subject.