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Cooling the trouble with sterndrive impellers in AZ.

G

Glenn in AZ

New member
The best impeller Advice I've heard is... "Change it every year." Wouldn't it be NICE if the impeller were more accessible? Say on the back of a pump on the front of the engine?
I think NICE is when and if, it doesn't consume a lot of Time, Inconvenience and or $$ Money. The Question is: how would I combine a Bravo raw water pump, the right bracket, a V belt pully together on the front of the MerCruiser Gen1 4.3 185Hp w/P.S. that I leave in AZ every summer?
Thanks in advance for anything you may offer, Thanks! Glenn
 
I am not saying that this is the one to buy, it is an example of a Crankshaft driven water pump impeller that fits to crankshaft at front of engine. No need for pulley or additional belt. all you would need to do is re-route/replace two hoses. One hose from power steering cooler to input of impeller and one new hose from out put of impeller housing to input to thermostat housing where incoming water hose connects now.

marineenginedepot.com

Johnson F6B-9 Extra Flow Crankshaft Mounted Pump w/ Coolant Supply 10-24946-01 Marine Power

Crank driven raw water pump. For Repair Kit See Part Number 527246.
marineenginedepot.com marineenginedepot.com
 
I would suggest doing some research on the right one for you first and determine what hoses may be needed and then make a decision.
 
Following up with some questions.
first, I run a gen 1 alpha, my impeller last 4-5 years. Seasonal usage as I live in Mass. This also means it sits unused for about 8 months so the impeller can take a compressed shape which may be worse than bsing used most of the year.

1. Why would you need to replace the impeller every year?
2. Are you running through sandy shallow water?

I would think the impeller in AZ would last a very long time?
 
kghost said:
I would think the impeller in AZ would last a very long time?
Click to expand...

Why? That area has open water, but the heat would kill any elasticity that might allow the impeller to conform to the pump housing and provide adequate water pressure.
 
Glenn in AZ said:
The best impeller Advice I've heard is... "Change it every year." Wouldn't it be NICE if the impeller were more accessible? Say on the back of a pump on the front of the engine?
I think NICE is when and if, it doesn't consume a lot of Time, Inconvenience and or $$ Money. The Question is: how would I combine a Bravo raw water pump, the right bracket, a V belt pully together on the front of the MerCruiser Gen1 4.3 185Hp w/P.S. that I leave in AZ every summer?
Thanks in advance for anything you may offer, Thanks! Glenn
Click to expand...
One question- what part of AZ?

If you're mechanically inclined (and physically able), I would recommend doing it for yourself or talking with other boaters to find out who does this for them. Some have money to burn, so they don't mind paying a lot, but many don't. However, it's a necessary expense if you don't want to end up with an impeller like the one in the photo.

This was in my '84 4Winns- the previous owner is one of the people who shouldn't own a boat and it was neglected for so long that when he used the boat the last time, he bent an exhaust valve, warped the head and killed every piece of rubber or plastic after the exhaust, including all of the bellows, the shutter valve, water pump upper housing, water pocket and water tube. I replaced the bearing carrier just because the cost of new seals/o-ring and bearings was more than my cost for a new one.
 

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The impeller I removed was working fine before we left the boat for a summer in in our semi shaded back yard. The impeller was rock hard with three vanes folded over. We discussed making a shade enclosure for the stern drive unit, painting it white, storing it indoors, and more...
My "best advice" (A pro) suggested having someone bump the starter once a month to prevent it from taking a set.
 
Glenn in AZ said:
The impeller I removed was working fine before we left the boat for a summer in in our semi shaded back yard. The impeller was rock hard with three vanes folded over. We discussed making a shade enclosure for the stern drive unit, painting it white, storing it indoors, and more...
My "best advice" (A pro) suggested having someone bump the starter once a month to prevent it from taking a set.
Click to expand...
To be honest, I think ambient temperature will kill an impeller as fast as direct sunlight- they work they don't, IME.

I have always thought these impellers should be made from more durable material.

If you can lubricate the impeller (RV antifreeze can do that), it won't dry out as quickly and it won't stick to the stainless cup in the raw water pump. If you replace an impeller, lubricate it with Glycerine (this is included in the box with several brands of replacement parts, including Volvo-Penta. If you need some, or if you're a woodworker who works with veneer, Rockler woodworking stores sell it.
 
Glenn in AZ said:
The impeller I removed was working fine before we left the boat for a summer in in our semi shaded back yard. The impeller was rock hard with three vanes folded over. We discussed making a shade enclosure for the stern drive unit, painting it white, storing it indoors, and more...
My "best advice" (A pro) suggested having someone bump the starter once a month to prevent it from taking a set.
Click to expand...
RE: One question- what part of AZ?
Gold Canyon AZ, 85118, generally Phoenix minus 5 deg F
 
Glenn in AZ said:
RE: One question- what part of AZ?
Gold Canyon AZ, 85118, generally Phoenix minus 5 deg F
Click to expand...
Near AJ, right? I Have been out there- a friend lives in AJ, which he calls 'Malfunction Junction'.

You might be able to try using a wrap for the outdrive with reflective Mylar, like Reflectix inside. I don't know if the critters will try to nest inside, but with draw strings, they may stay out. If you know anyone who uses a sewing machine or an upholstery shop, they should be able to make this from awning canvas, preferably a light color.
 
I see, You left out the part of leaving on a trailer for periods of time.
Thought you kept it in the water.

Maybe make a special tank that will keep 80% of the drive submerged and you can add cool water as needed. This may keep the impeller and housing nice and cool

Then simply add cool water every .couple days or how ever often it needs to be cooled/replaced to keep pump housing cool.
 
siluetae137 said:
It's on backorder, this frontal impeller idea must be trending!
Click to expand...
Thanks for a whole lotta great ideas Everyone!!! Your probably helping lot's of others too.
And..I'm going for the crank mount pump Idea; easy; simple; and Impeller change wil be easier than opening the eng cover! So...
Murphy's Law: I may never need to change the impeller, right?
The fresh water will come though the stern drive. So what should I do to let it flow properly?
 
You may have to research that.

Bravo's and inboards which typically would have a engine mounted impeller pump get the water from, (Bravo haa no impeller housing so its a straight draw thru drive) or and this includes inboards, they use a thru hull or at tramsom pick up.

So you may need to bypass the alpha impeller if removing the impeller from the housing but leaving the housing in place, doesnt supply enough water...
Then you would need a transom or thru hull pick up which would connect directly to the new pump system.

I am not sure so I am pointing out what may be an issue
 
Also, a engine mounted pump, the pick up hose ia usually steel reinforced so it does not collapse under the vacuum of the pump!! Not 100% sure of that on the bravo's but am sure of that on inboards
 
Glycerin's boiling point = 554 °F (not even Death Valley gets that hot). Also, glycerin is hyperosmotic, meaning it draws water into itself, making it the perfect fluid to summerize an impeller in AZ! However, it's freezing/melting point = 64 ° F, so it will solidify in the cold (it takes extended exposure to cold temps probably below 40 ° F to freeze). Also, prolonged periods of freezing/melting speeds up decomposition to acrolein, which is toxic.
Seriously, if I was leaving my boat in AZ over the summer, I would consider adding glycerin to the metal insert the impeller rotates in, enough to fill the voids.
 
depending on your engine compartment set up you maybe trading one inconvenience for another.

What brand impellers are you using ? Also think generally when you use a belt or crank driven pump on an alpha like with closed cooling, it is recommended that the impeller in the drive be left in place and the water hose from bellhousing to gimbal be cut. This allows water to flow through the drive and cool it
 
Glenn in AZ said:
Thanks for a whole lotta great ideas Everyone!!! Your probably helping lot's of others too.
And..I'm going for the crank mount pump Idea; easy; simple; and Impeller change wil be easier than opening the eng cover! So...
Murphy's Law: I may never need to change the impeller, right?
The fresh water will come though the stern drive. So what should I do to let it flow properly?
Click to expand...
No, the impeller HAS TO be changed periodically- they don't live forever and I have seen the vanes become too weak to push water in only a couple of years, here in the Milwaukee area, regardless of whether the pump was in the gear housing or on the engine. Leaving it alone is a very bad idea and the damage done to my engine by the previous owner is what happens to a 2.5l/3.0l, but the larger engines have more cylinders, so more heat is generated and needs to be removed. As I posted, a dead impeller takes out every piece of rubber and plastic after the exhaust manifolds and I have seen exhaust tubes in ski boats/bellows in stern drives that perforated because the engine was running at high RPM.

The engine-mounted pump receives water from the lower gear housing as it comes out through the transom, as it does now. You would send water from its output port to the thermostat cover where the existing water hose is attached. Look on the existing water hose for an oil cooler- if you have one, this is where the water supply comes from and you'll need to replace the hose of it's much too short, cut it if it's much too long.

An option to sending water from the lower gearcase to the pump is to install a through-hull water pickup like the ones in yachts and ski boats. If you do that, I would highly recommend adding a strainer for catching weeds and other debris.

O'Toole's Corollary to Murphy's Law- "Murphy was an optimist".

Putting the raw water pump on the engine can be great, but some boats don't have a lot of space to install it AND service it. I worked on a Larson that had the hoses so close to a stringer that they couldn't be reattached with the hose clamps in place, they had to be left off and reinstalled after the hoses were on the pump. That wouldn't have been so bad if they had created an opening in a panel that allowed reaching them from the front, but they were in a place where someone my size could only reach in with one hand.
 
kghost said:
I would suggest doing some research on the right one for you first and determine what hoses may be needed and then make a decision.
Click to expand...
Thanks and it looks like a real good setup for that pump. Just some hose and clamps is all Ill need.
Still wondering what mods are needed inside the sterndrive. Just remove the impeller?
 
Dieter said:
depending on your engine compartment set up you maybe trading one inconvenience for another.

What brand impellers are you using ? Also think generally when you use a belt or crank driven pump on an alpha like with closed cooling, it is recommended that the impeller in the drive be left in place and the water hose from bellhousing to gimbal be cut. This allows water to flow through the drive and cool it
Click to expand...
Re: What brand impellers are you using ?
The one i just replaced came inthe SEI 06 sterndrive new replacement done in Oregon Spring 2022. Came to gold canyon AZ shortly after. Ran alot in canyon lake.. deep clean no sand then stored in back yard all summer 2023.
 
Question when covnerting SEI sterndrive to a crank driven cooling pump (fresh water). Should the impeller in the lower unit be removed to allow better flow? Any other changes? Thanks
 
So I shoud remove the impller and the waterpump Housing in the sterndrive when I convert to a crank mounted cooling pump?
(Freshwater system)
Anything else is appreshiated. Thanks
 
You really cant have two impellers.
The one in the drive will have the same issue you are posting about.

So, if a engine mount impller pump is used at a minimum, No impeller in the outdrive.

The question is which I already asked/stated was, will it work in a alpha outdrive.

Your final answer may be, you need a thru hull or transom mounted water pick up.
 
Glenn in AZ said:
Question when covnerting SEI sterndrive to a crank driven cooling pump (fresh water). Should the impeller in the lower unit be removed to allow better flow? Any other changes? Thanks
Click to expand...
You might want to call SEI about that. Pulling water is very different from pushing it, same for gas and this is the reason many boats and ALL cars have in-tank fuel pump- it's a better way of maintaining flow. This is the reason many boats have a fresh water pickup fitting in the hull- under way, the fitting acts like a scoop and flow is much better than trying to move enough water from the slots in the lower gear case.
 
Glenn in AZ said:
The best impeller Advice I've heard is... "Change it every year." Wouldn't it be NICE if the impeller were more accessible? Say on the back of a pump on the front of the engine?
I think NICE is when and if, it doesn't consume a lot of Time, Inconvenience and or $$ Money. The Question is: how would I combine a Bravo raw water pump, the right bracket, a V belt pully together on the front of the MerCruiser Gen1 4.3 185Hp w/P.S. that I leave in AZ every summer?
Thanks in advance for anything you may offer, Thanks! Glenn
Click to expand...
Ayuh,..... Not really an answer to yer question, but a cure for yer problem, that worked very well for me,.....
I installed a Globe, run dry impeller in my Alpha 1 drive years ago,.....
It's still pumping good water, better than 10 years later,.....
 
bondo said:
Ayuh,..... Not really an answer to yer question, but a cure for yer problem, that worked very well for me,.....
I installed a Globe, run dry impeller in my Alpha 1 drive years ago,.....
It's still pumping good water, better than 10 years later,.....
Click to expand...
Interesting. It's a floppy vane right? It has to be in Alpha 2 assume same for A1. Is it just made of some material that won't heat and melt?
 
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