Impeller replacement

[Travis71]

So as I mentioned in another thread I have rectified my shifting issue...YAY!!

when I had it out yesterday my temperature gauge was registering quite a bit higher than it was before. I initially chalked it up to the fact that I had recently installed a new temperature sender because the old one seemed a bit erratic. I did some searches on the forum and decided I should probably check my impeller to make sure it was still intact just to be sure. My impeller is intact although it does have a crack in it and the fins Are permanently bent, i.e. they don’t spring back when removed from the housing.

I would like to go ahead and replace the impeller while I have it apart, so I am wondering if the OMC impeller is unique or if sterndrive impellers are somewhat universal. The reason I ask is because I would rather not be waiting for or five days to get a new part through the mail.

My other question concerns what else I can do to ensure that my coolant system is working properly. I want to make sure that water is circulating the way it should but I am not sure how to go about that. Any help that can be provided is much appreciated!

 

[racerone]

They are NOT universal.----You have to order the correct ( factory ) part in my opinion.-----If blades do not flex properly you will have temperature issues at idle RPM.

 

[Scott Danforth]

just for a jabsco pump, there are about 20 different impeller designs. couple that with the proprietary OMC design for cobra or the Alpha design from mercruiser, etc. and there are well over a few hundred types of impellers.

you need the proper impeller listed for your 1989 drive. and buy the OEM, not Sierra or others

 

[kenny nunez]

With the engine cold turn on the ignition and watch how much the temperature gauge registers. Sometimes a new gauge is not compatible with the sender and reads higher.
The OEM parts are the best but if you need something just to get it back together try the Sierra stuff and order the OEM parts. 984461 should fix you up.
There should be an aftermarket marine dealer in your area that will have the impeller kit.
Sierra # 18-3058 impeller. Or 18-3348 complete kit. Or 18-3212-1d partial kit.

 

[Travis71]

Am I correct in assuming that impeller housing should be round?

so should I get the kit that comes with new housing gaskets and all?

 

[Travis71]

With the engine cold turn on the ignition and watch how much the temperature gauge registers. Sometimes a new gauge is not compatible with the sender and reads higher.
The OEM parts are the best but if you need something just to get it back together try the Sierra stuff and order the OEM parts. 984461 should fix you up.
There should be an aftermarket marine dealer in your area that will have the impeller kit.
Sierra # 18-3058 impeller. Or 18-3348 complete kit. Or 18-3212-1d partial kit.

With the key off it reads 130. When I turn the key on it pegs left (minimum).

disconnected wire from from sending unit, same thing.

When I ground the connecting wire to the engine the gauge pegs to the right (maximum).

 

[Scott Danforth]

no, the impeller housing isnt round

yes, based on the permenant set of your impeller, you need a new kit

Kenny has you fixed up with part numbers

based on your description of your temp gauge, something is not right there.

 

[bruceb58]

based on your description of your temp gauge, something is not right there.

What makes you think that?

Minimum with the key on. Also minimum with the wire removed. Ground at the engine and its maximum.

 

[Scott Danforth]

OP should get different readings with the gauge sender wire on vs off at the back of the meter.

 

[Lou C]

You don’t need to change the housing unless the boat was run out of water and the housing overheated and started to distort. I would change the wear plate; cage; impeller and that oring gasket. I use OMC gasket sealer on the bolts and to “glue” the cage in the housing. Although the manual says to use the same gasket sealer to seal the oring gasket to the housing sometimes they curl up and don’t want to lay flat in the groove. What I do is put a bead of OMC triple guard grease in the groove in the housing and that holds the oring in place when you assemble it.
after you’re done, leave the cover off and run it on the water hose to check for leaks around the housing. I find as long as you don’t suck up sand these will last at least 3 seasons.

 

[Travis71]

Just a little update...

I put the original temperature sending unit back in and attached a thermometer to the water circulation hose. At idle on the garden hose I was reading around 140-150 on the thermometer and the boat temperature gauge. Just out of curiosity I put the other sending unit on and the boat gauge jumped up to over 200. So obviously the sending unit is not compatible with my gauge...lesson learned, get OEM parts.

 

[Travis71]

With the engine cold turn on the ignition and watch how much the temperature gauge registers. Sometimes a new gauge is not compatible with the sender and reads higher.
The OEM parts are the best but if you need something just to get it back together try the Sierra stuff and order the OEM parts. 984461 should fix you up.
There should be an aftermarket marine dealer in your area that will have the impeller kit.
Sierra # 18-3058 impeller. Or 18-3348 complete kit. Or 18-3212-1d partial kit.

Got an OEM kit ordered on Friday, will be here Tuesday!

 

[Travis71]

Got the impeller kit installed and it works great! I can definitely tell that the new impeller is moving more water up to the engine because I used to see lots of water squirting out around the muffs on the lower unit intake screens, and now I don't see any escaping at all.

The one thing I noticed is that water immediately started coming out through the exhaust bellows before the engine had a chance to warm up. I read some other posts and as I understand it, the thermostat is supposed to stay closed and keep all water in the engine block until it reaches operating temperatures and then it will open up to allow water to go out through the exhaust.

I can't say I paid super close attention before, but it seems like ti took awhile before water started coming out the exhaust. I may be over analyzing it, but I don't want to be caught off guard if something isn't working properly.

What do you think??

 

[Lou C]

It's normal because remember even with the engine cold and stat closed, all the incoming raw water being pumped has to exit, so it goes out the exhaust nearly immediately after starting. Then when the engine warms up and the stat opens, hot water exits the stat housing and exits the exhaust system. So if your exhaust was not drained and had water in it, as soon as you start it like within 5 sec you'll see water....

https://www.dropbox.com/s/ysj65t93un6dyuy/Cobra running on the water hose.MOV?dl=0

 

[Travis71]

It's normal because remember even with the engine cold and stat closed, all the incoming raw water being pumped has to exit, so it goes out the exhaust nearly immediately after starting. Then when the engine warms up and the stat opens, hot water exits the stat housing and exits the exhaust system. So if your exhaust was not drained and had water in it, as soon as you start it like within 5 sec you'll see water....

https://www.dropbox.com/s/ysj65t93un6dyuy/Cobra running on the water hose.MOV?dl=0

Thanks Lou! Just wanted to make sure everything was operating normally!

 

[Lou C]

This shows how the OMC/Volvo stat housing design works, when the engine is cold and the stat is closed, all the incoming water pumped by the impeller gets pumped out the exhaust system which is why you see water right away, unless the whole system was drained. Then when the stat opens, warm engine from the block/heads exits the exhaust and cool water is drawn in from the stat housing via the front circulating pump, it flows through the block and heads picking up the heat of combustion and then leaves via the open 'stat and exhaust system....

Notice the bypass passage....see how water flows through it with a cold engine but not with a warm engine...when you change the thermostat, good idea to make sure it is open and not necked down with corrosion. In salt water regions you wind up changing these housings at about the same time as exhaust elbows...