Change Impeller?

[Guest]

Hello

I think that this is an easy question, but here goes.

My boat is a '95 and I have no clue when the impeller was ever changed on it. I ran it 140 hrs last year, almost all of it super slow.

I am thinking that I should change the impeller this spring, in hopes that I won't get stranded with an over-heated motor.

Since I have no idea how old it is, I just thought that I should establish a baseline and just change it every,,,what 2/3 yrs maybe?

I'd guess that prevention is the key here,,,,,I am paranoid about getting stuck, especially if I am alone,,,,I don't need THAT. :thumb

Any recommendations? Do I carry a spare? (Can I actually change it on the water?) How often to change 'em w/normal use?

Thanks kindly for any insight, it'll be appreciated.

Sarah

[boatworkfl]

Change it and carry a spare, not worth the risk of an engine over heat. I tell the charter boat captains and heavy users to change it every year, 2 years at the most for light to med use.

[Guest]

As far as changing it in the water, as long as the impeller sits above the water level, then you should be fine. Others will probably chime in....

:-)

[boatworkfl]

kellynm wrote:
As far as changing it in the water, as long as the impeller sits above the water level, then you should be fine. Others will probably chime in....

:-)

you can turn the seacock off when changing the impeller. I am not well versed with what boats have outdrives, have only worked on inboards, some OB.

[LostLeader]

Alpha 1 gen II the impeller is in the outdrive. Can't be done on the water. Yes, carry a spare, just in case. Some people change impellers every year, others every two years, others longer.

A sad note, just because you changed the impeller doesn't means that the new impeller is working properly. I had a new impeller that was bad after I installed it. Found bits of rubber from impeller during flushing. Changed to new impeller. Still low water flow on earmuffs. Took boat out to test, engine got warmer then I would have liked. Double checked install. Still low water flow. Got new impeller and re-installed newer impeller. Great water flow off earmuffs. Took boat out for a spin, no problems. The bad impeller looked good measured up fine with the other impellers, rubber was good. Just a weird bad impeller.

[Guest]

Alpha 1, gen 2???? I would not try changing while in the water....you have a trailer, correct? There are some videos on YouTube showing how.... I did my own last year while on the hard....bravo 2s have the remote pump you can change while splashed... And I had a cobra on my 2455 that I could have changed in the water, but with a trailer, why would I?.....

Just my 2 cents.....

Mike

[Guest]

Alpha 1, GenII outdrive. When you remove the lower half of the outdrive, you will dump the gear lube is you haven't already drained it. There is an oil passage between the two halves of the outdrive with an o-ring seal. Best to do with the boat on the hard.

Also good time to remove the prop and grease the splines and replace all of the anodes on the outdrive. One on the gear case that goes around the prop shaft that you can get to with the prop off. .The one in the bottom of the anti-ventalation plate (most people refer to this as the anti-cavitation plate), you'll have to remove this anode to get to one of the bolts that holds the lower gear case to the upper case.

Also, when I replace the impeller, I make sure I have four replacement nuts for the four nuts you can see from the outside of the outdrive. These nuts are chrome plated brass and the last time I replaced the impeller on my boat, all four of those nuts developed cracks and would not tighten.

[Guest]

Thank you !!

Great advice guys, and much appreciated too.

Many Thanks!

Sarah

[cwiert]

Yup.. It's in the outdrive. You should replace to establish a baseline. I guess every 3-4 years is a good increment. FWIW, my buddy has a sea ray 180 with the alpha 1 outdrive. He never changed it. Ever. The boat is over 10 years old. I told him last year that he needed to do it ASAP. So he did over this winter and the thing was in perfect condition. Fresh water boat, so that helped. I'm not saying that is the case for all impellers, but like everything else, your results may vary.

Best bet is to just get it done for peace of mind.

John

[Guest]

I've got an impeller for sale - Willing to sell it to you at one heck of a discount.

[2850Bounty]

Sarah, this is what your A drive impeller looks like.

The vanes on the A drive impeller are short and rather stiff compared to many others.

(examply image only)



Here is a more coventional style impeller shown in a pump body that uses a cam to flex and fold the vanes over.

Your A drive impeller vanes fold similarly, but instead of the cam folding them....., the pump body is eccentrically positioned around the shaft (no cam).

A very similar fold occurs, and is what causes the "set" during prolonged non-use.



IMO, the A drive impeller is more prone to taking this set than many other style impellers.

What this means to me, is that of all the different style impellers, this one is best if at least inspected more frequently.

The "set" that these will take occurs more so from "non-use" than actual use.

This also means that you should not let anyone talk you into a new impeller during lay-up. That is a lousy time to be installing a new impeller only to let it sit at rest within the pump body with three or four vanes folded over.

Instead, put this on your re-commissioning list, and begin your season with a fresh impeller.

Keeping a spare on board (as the guys have said) is great, but will only help you if you have a way to pull the boat out of the water.

This is very crude example of how a flexible vane impeller pump works.



Pump rotation here is reversed here, so you'll want to flip this around in your mind.







Sarah, I figure that the more info you have, the better you'll understand just what your sea water pump is doing, and how it does it.

If you should encounter shallow water, and if your prop should churn up bottom sediment, this is when you'll want to watch things closely.

Heavy sediment drawn into the pump can damage not only the impeller, but may also damage the pump housing.

It can also carry this sediment into the engine and exhaust manifold cooling side.

Otherwise, with normal use an impeller will last quite a while.

I'll assume that you already know that the sea water pump must be wet in order to fire an engine up. A dry impeller can self destruct in as little as 10 seconds of run time.

Here are two articles on impeller pumps.

http://www.boattest.com/Resources/view_news.aspx?NewsID=3206

http://www.globecomposite.com/files/BW_impeller_article.pdf

[Chief_Alen]

Some kits come with a shift shaft bushing. Actually a seal for the shift shaft. Replace that also. Me i would change out the whole pump housing and all.

See every time you shift the shaft wiggles and the bushing wears.

Click below for the lowest price kit i can find just got one for my friends gen 2. I have bought many many items from them.

http://bpi.ebasicpower.com/p/GLM12414

[Guest]

Robert K wrote:
I've got an impeller for sale - Willing to sell it to you at one heck of a discount.

I'm guessing that I don't want mine to look like that!

[Guest]

2850Bounty wrote:
Sarah, this is what your A drive impeller looks like.

The vanes on the A drive impeller are short and rather stiff compared to many others.

(examply image only)

Here is a more coventional style impeller shown in a pump body that uses a cam to flex and fold the vanes over.

Your A drive impeller vanes fold similarly, but instead of the cam folding them....., the pump body is eccentrically positioned around the shaft (no cam).

A very similar fold occurs, and is what causes the "set" during prolonged non-use.

IMO, the A drive impeller is more prone to taking this set than many other style impellers.

What this means to me, is that of all the different style impellers, this one is best if at least inspected more frequently.

The "set" that these will take occurs more so from "non-use" than actual use.

This also means that you should not let anyone talk you into a new impeller during lay-up. That is a lousy time to be installing a new impeller only to let it sit at rest within the pump body with three or four vanes folded over.

Instead, put this on your re-commissioning list, and begin your season with a fresh impeller.

Keeping a spare on board (as the guys have said) is great, but will only help you if you have a way to pull the boat out of the water.

This is very crude example of how a flexible vane impeller pump works.

Pump rotation here is reversed here, so you'll want to flip this around in your mind.

Sarah, I figure that the more info you have, the better you'll understand just what your sea water pump is doing, and how it does it.

If you should encounter shallow water, and if your prop should churn up bottom sediment, this is when you'll want to watch things closely.

Heavy sediment drawn into the pump can damage not only the impeller, but may also damage the pump housing.

It can also carry this sediment into the engine and exhaust manifold cooling side.

Otherwise, with normal use an impeller will last quite a while.

I'll assume that you already know that the sea water pump must be wet in order to fire an engine up. A dry impeller can self destruct in as little as 10 seconds of run time.

Here are two articles on impeller pumps.

http://www.boattest.com/Resources/view_news.aspx?NewsID=3206

http://www.globecomposite.com/files/...er_article.pdf

Doug! Awesome,,,,,,,,thank you.

Good stuff and it makes sense - maybe it's wise to just take it out for winter? Or is it a PITA to get to?

Thanks very kindly, I am educated now

Sarah

[2850Bounty]

LazyCrusr wrote:
Doug! Awesome,,,,,,,,thank you.

Good stuff and it makes sense - maybe it's wise to just take it out for winter? Or is it a PITA to get to?

Sarah, you are always welcome, and you can call me Doug if you'd like to!

As for removing the impeller for the winter, this is easiest for us who have engine mounted pumps.

I've been doing this for years.

For the A drive, it would mean leaving the lower unit off for the winter, or doing the R&R twice.

It can extend impeller life.