Frequency of impeller replacement?

[JASinIL2006]

While I'm sitting around being cold and hearing about the blizzard out East, I'd like to take care of any boat maintenance to keep me busy.

In particular, I'm trying to figure out if I need to replace my impeller this off-season. The boat lives on a trailer and sees about 50-60 hours of use each year in freshwater (Mississippi & Illinois rivers, in addition to a lake in Canada). The current impeller has been in for two full seasons and I've seen no changes in normal operating temps for the boat. Not too many other boaters around here seem to do preventative maintenance, so I don't really have anybody to ask.

Thoughts? The drive is a Alpha One Gen 2 on a 350 Mag engine.

Thanks!

Jim

 

[dingbat]

I change my impeller when I see a 15-20% drop in my water pressure at idle. It been as long as 4 years and as short as 2.

Not being used is harder on them use

 

[stonyloam]

The "book" says disassemble and inspect the seawater pump " annually or every 100 hours". I think that is a little overkill but after 2 years with 100+ hours on it, probably a good idea to change it out. When you see a change in operating temperature it is already too late.

 

[bilge rat jim]

3-4 years, more frequently if you operate in silty or sandy conditions. You should do a "pump kit replacement", which includes wear plate, pump cup, seals and gaskets every second time,

 

[achris]

3-4 years, more frequently if you operate in silty or sandy conditions. You should do a "pump kit replacement", which includes wear plate, pump cup, seals and gaskets every second time,

That's the one. You quoted saying it's a Gen II, they are 'long vane' impellers and last considerably longer that the early impellers. Even the Merc owners' manuals are now saying 3 years between impeller inspections... (note that's 'inspection', not replacement)...

Chris.......

 

[gm280]

Such a subjective topic with so many "best ways" to do such work. It is nearly impossible to tell anybody when to change their water impellor or total pump assembly. Only you know what your engine has been through since last change. So if you think it is time, then it is...period! I've seen folks go for five to ten years and have zero issues or problems, and I'm equally sure some have had problems in a few months. So only you can make such decisions. I hear the norm being around two to three years. But that is only what I read...

 

[HT32BSX115]

The current impeller has been in for two full seasons and I've seen no changes in normal operating temps for the boat. Not too many other boaters around here seem to do preventative maintenance, so I don't really have anybody to ask.

Howdy Jim,

You probably already know most operator manuals for the Alpha indicate to change the impeller when "worn"
According to Mercury, annually or 100hrs

Disassemble and inspect seawater pump and replace worn
components.

Some people have waited 3 or 4 years, some have gone longer............

(My brother changed his raw water pump on his Mercrcury inboard engine[Bravo pump] 8 years after he bought the boat new!!. He did it in the middle of the lake using a "Crescent-Wrench, a pair of pliers and a rag stuffed in the inlet hose to keep the boat from sinking" !!!!!!)


I wouldn't go that long. While I do not "disassemble and inspect" my Bravo pump every year I usually replace it every other year or so.

Using a gage to measure pressure would be helpful but if the impeller disintegrates, the gage will only indicate that an overheat is impending............ and if you're not looking at the pressure gage when it happens, you probably also won't notice the temp gage "pegged"!! and if you're not looking at that gage, you'll absolutely know it when you smell burning rubber(in the exhaust system)

If you want to use raw water pump pressure to determine when you should "look" at the impeller, get a pressure switch and connect it to a loud alarm bell or beeper etc.......but it STILL won't help you much if you're on the water with no new impeller and no tools!! (it's a little hard to change an Alpha impeller with the boat in the middle of the lake........[DON'T DROP THAT LOWER in deep water!!!!!!]

If I was operating in Salt, I would inspect that impeller every year like Mercury suggests and since it's so easy to change, I might just change it at a max of 3 years..........(last Alpha impeller I changed had been in there about 5 years and it "looked" fine)

It seems the Gen-II impeller is a little softer rubber compound so it seems to live longer....

Considering that an after market GEN-II impeller is less than $20 and the entire kit is around $35, even changing one every year is not all that expensive.........

With the alternative being a tow (or up a creek without a paddle), I lean toward preventive maintenance.


Regards,


Rick

 

[thumpar]

On my Alpha I changed the impeller every other year. I plan on letting my Bravo go a little longer but I carry a spare impeller with me and can change it on the water as Rick pointed out.

 

[jkust]

I did my Alpha 1 at about 100 hours as a preventative but it took about 8 years to get 100 hour on the dial so was getting old.

 

[thumpar]

We would only put in about 15 hours on our boat with the alpha but I still changed the impeller every other year.

 

[achris]

The OP has an Alpha One GEN II.. The impeller is a completely different animal to the impeller in an Alpha One.... Yes, Alpha One impellers need to be changed every other year, at least. But the Gen II impeller is a long vane or 'floppy' impeller and has a considerably longer life. Most will last the 3 years recommended service interval without any problem whatsoever.

I replaced mine at 7 years (having checked it at 3) and it still didn't have a single wear mark on the blade tips. I only replaced it because I had a spare in the toolbox... Had I not, new gaskets would have gone in and the original impeller would still be there today...

Chris.........

 

[HT32BSX115]

The OP has an Alpha One GEN II
I replaced mine at 7 years (having checked it at 3) and it still didn't have a single wear mark on the blade tips. I only replaced it because I had a spare in the toolbox... Had I not, new gaskets would have gone in and the original impeller would still be there today...

Chris.........

I misspoke on that GEN-II impeller I replaced on my friends drive a few years ago..... it wasn't 5 years...........he'd had the boat approx 8 years and didn't know the impeller should even be checked......It was in pretty good shape I must say. I am guessing that the GEN-II impellers absolutely will go longer than any Alpha-1 or Bravo pump.......

This has reminded me that I should check the impeller in my little 9.8hp Tohatsu outboard motor..........I bought it new in 2003. I guess I should get a raw water pump kit for it...........It's only been 11 years though..........

 

[Starcraft5834]

I did my Alpha 1 at about 100 hours as a preventative but it took about 8 years to get 100 hour on the dial so was getting old.

that was my thought...100hrs? Im out about 12 times per year with mine,, hr running time each time maybe? problably less.. that's about 8 years. I had mine replaced 2 years ago.. thought this coming year might do it again,,, if no issues with running temp will probably skip it.... Ive only got about 20 hrs on the pump in there, it only goes in fresh water (and deep), no dirt/grime where I usually go

 

[lg260ss]

On my Alpha I changed the impeller every other year. I plan on letting my Bravo go a little longer but I carry a spare impeller with me and can change it on the water as Rick pointed out.

I wouldn't let your Bravo go any longer than 2 years. The Bravo pumps are not nearly as robust as the Alpha pumps and because they are engine mounted they don't receive the supply water as quickly as the drive mounted alpha. And if you wait until it fails, you'll have little pieces of impeller to fish out of the system.

 

[thumpar]

I wouldn't let your Bravo go any longer than 2 years. The Bravo pumps are not nearly as robust as the Alpha pumps and because they are engine mounted they don't receive the supply water as quickly as the drive mounted alpha. And if you wait until it fails, you'll have little pieces of impeller to fish out of the system.

I understand that. I had mine fail once. The only reason I will let the Bravo go longer is because I know I can change it on the lake in the worst case but we only get about 15-20 hours of use a year of drive time. We mostly just sit and relax.

 

[JASinIL2006]

This is very helpful, thanks! I think I'll go another season before I open the drive and check it out. I changed the complete pump assembly after I bought the boat, so I know it all was in good shape.

Thanks again!

Jim

 

[Scott Danforth]

its called preventative maintenance for a reason. replacing the impeller every few years is less expensive than getting a tow.

my suggestions, fresh water, 5 years max, more frequent if you do not go boating at least once a month. in salt water, every 2 years, more frequent if you do not go boating at least once a month.

 

[Tail_Gunner]

I once was of the thought every couple of years... until that is i had one blow 3months into the season. Once a year for this guy...ruin a good day on the water...BS....Dig out impeller parts on my day off mid summer....BS...... one blown motor midsummer over a 50 part..nope. Those pumps actually pump high volumes of water... and those vanes...well there not high on my list shall we say....Ohh the drive is a volvo.

 

[achris]

Bravo pumps, Alpha One pumps and Volvo 'japsco' style pumps have short stiff vanes. They damage easily and are prone to breaking blades off. The soft long floppy vanes of the Gen II drives is so different to those other impeller... You can't compare apples with oranges... The pump housing side pressure exerted by the blades of the Gen II impellers is less than half that of the others, so even run dry they suffer very little damage... The Gen II pump housing is also stainless steel, not plastic, so there's no distortion from being heated up, no plastic to melt.

The only thing to remember with these pumps is that you MUST use the alignment pins when re-installing the housing. If you don't you risk getting the housing off centre, which will lead to overheats (impeller not working correctly and providing less water to the engine), and the housing rubbing on the drive-shaft, cause a groove in the shaft...

Chris......

 

[agallant80]

Every other year on my Bravo3