Impeller replacement interval?

[1960vw]

Being new to I/O's on a 3.0 Merc in my 1993 Starcraft Elite 171, do you recommend changing the impeller based on hours used or by set time frame? I had a shop replace one and he recommended every other year under " normal " usage. I have about 15-20 hrs on it. Thanks!

 

[dubs283]

Re: Impeller replacement interval?

do you recommend changing the impeller based on hours used or by set time frame?

yes

 

[Bondo]

Re: Impeller replacement interval?

I had a shop replace one and he recommended every other year under " normal " usage.

Ayuh,... At every other year, the rubber is getting Hard,+ just don't work so well anymore...
Hours of use is less of the issue....

 

[zbnutcase]

Re: Impeller replacement interval?

The less a boat is used, the more frequent PM is needed. 'nutcase

 

[JustJason]

Re: Impeller replacement interval?

Merc's spec is 2 years or 200 hours, whichever comes first.

 

[elkhunter338]

Re: Impeller replacement interval?

Dont really know, before you have trouble.
I have ran my outboard since 2001 with the orginal waterpump, my 1995 outboard is going to get it's first new water pump this winter. my I/O had a 5 year old water pump in it with no problems.
My grandpa ran a merc. for many years with out replacing the water with no problems. The quality of the water pump I am sure makes a difference and like all other stuff we buy these days I am sure the old orginal water pumps last longer than the replacements we buy today.
I will probably plan on changing mine in my 3.0l every 4 years.

 

[1960vw]

Re: Impeller replacement interval?

WOW! Thanks for the response. I think the two year rule sounds good. I will follow that.

 

[cr2k]

Re: Impeller replacement interval?

Dont really know, before you have trouble.
I have ran my outboard since 2001 with the orginal waterpump, my 1995 outboard is going to get it's first new water pump this winter. my I/O had a 5 year old water pump in it with no problems.
My grandpa ran a merc. for many years with out replacing the water with no problems. The quality of the water pump I am sure makes a difference and like all other stuff we buy these days I am sure the old orginal water pumps last longer than the replacements we buy today.
I will probably plan on changing mine in my 3.0l every 4 years.

Hope that works out for you...I would carry tow insurance or some good paddles just in case.

 

[intrepidvoyager]

Re: Impeller replacement interval?

for what its worth ....what I have found over the years is there is really no set failure hours ...... i have seen them go after one season and some can last for years ..... to avoid problems I agree with the 2 season rule ..However I would invest in an IR thermometer so you can every once and a while check your riser temps during the season ......Higher than normal riser temps are usually a sign of impellor deterioration or riser flow issues both of which should be dealt with ASAP.

The IR thermo can also be used to check ALL ASPECTS OF THE COOLING SYSTEM including thermostat operation, etc ...

here is another use i pulled off the web ...

Some problems such as engine misfire can be time-consuming to troubleshoot. Isolating a misfire to a specific cylinder usually requires a power balance test (which is not easy to perform on some of today's distributorless ignition systems) or observing ignition patterns on an oscilloscope (which requires an expensive scope and making the necessary hookups). But now there is an easier way. Just use an infrared thermometer to measure and compare the temperature of the exhaust at each exhaust port. A misfiring cylinder does not produce as much heat energy as a good cylinder, so the exhaust from a weak cylinder will not be as hot as that from cylinders that are firing normally.

To find the misfire, aim the gun at each exhaust port on the manifold and squeeze the trigger. Note each reading and compare the results. Any cylinders that are misfiring will read significantly lower than the others.

Once you have identified the misfiring cylinder, you can zero in on the underlying cause. Remove and inspect the spark plug. If wet, the plug may be misfiring because of a bad plug wire, cracked distributor cap or bad coil on a DIS system. If the spark plug is fouled, the cylinder may have an oil consumption problem due to worn valve guides and/or rings. If the spark plug appears to be okay, the air/fuel mixture may be too lean. Check for a dirty or inoperative fuel injector, or an air leak around the injector seal. On older engines with carburetors, check for intake manifold air leaks. Another possibility may be a leaky valve. Check compression.

A VERY VERY HANDY TOOL TO HAVE AND CHRISTMAS IS COMING ...

 

[ziggy]

Re: Impeller replacement interval?

i just went and looked at s/m 2, 6 and 14.
2 and 6 are pre alpha and alpha1, which the op don't have.
14 is genII, which is what the op does have.



"maint. intervals

s/m 2 (pre alpha)- water pump (drive unit) and impeller, inspect. once a year by auth. merc dealer...

s/m 6 (alpha1)- sea water pickup pump - disassemble and inspect interval. whenever insufficient seawater flow is suspected. (if operating temp. exceeds normal range)

s/m 14(alhpa1 genII)- disassemble and inspect seawater pump and replace worn components. every 100 hrs or annually, whichever comes 1st. this one applies to the op. "



my own personal experience is with pre alpha. i think they're fragile at best. http://www.boatfix.com/merc/Bullet/87/87_14.pdf
i'f i'm gonna go inspect mine every year, i'm gonna replace it as it ain't that easy to go get. + this is my 3rd season of replacing yearly. all impellers have shown wear, i.e. taking a set or curl after only a years use + cracks on the inside of the curl. 2 of these impellers may have had 10 sec. dry run. one had low water pressure and smoked. it had glazed (hardened) rubber surface on the friction side (the outside of the curl) and loss of rubber (small chunks missing) transferring melted rubber to the inside of the water pump housing. + more severe cracks on inside of curl than the other 2.

granted i abused my impellers a shade. but for someone who uses their trailer boat often, yer just gonna forget or mishap by accident (i.e. low water pressure).

I've got a buddy with a '00 genII. he didn't replace his till '07 or '08. might have been '08. anyways, a long time. too long. his impeller looked at least as good as my best one. looked like he could have even run it longer. i was astonished. the gen II is a much larger impeller than alpha1 or pre alpha which are the same.

bottom line to me is alhpa1 and pre alpha i'd R&R once a year.
gen II. my gut feeling (since i've never owned a gen II) would be to follow the s/m. if however i found a respectable impeller after several years of inspections, i might consider extending the inspection.

if any overheat issues occur. the impeller is the first place to look..

fwiw, of all the gauges i have, the water temp gauge is always the first one i look at when checking operating conditions when on a run..

 

[CheapboatKev]

Re: Impeller replacement interval?

I would add that from I have been going through and advice from Ziggy and others..

Yearly impeller changes allow you to inspect your OD componets , U Joints grease, driveshaft wear..All things that can give you a chance to nip a future issue in the behind before it becomes a serious repair..



just dont drop your lower unit from the bench onto the driveway....long story...

 

[tkrfxr]

Re: Impeller replacement interval?

I ran 3 years with impellers, but they were removed from the crankshaft-mounted water pumps during winter lay-ups...could have gone longer too, but I was chicken. I kept them for spares, in case I need them ....

(volvo 5.7 OSxi's).

 

[Don S]

Re: Impeller replacement interval?

A Volvo impeller (along with the Alpha I and Pre Alpha drives) have a completely different kind of impeller. Both vane type, size and number.
I recommend to my customers with a Gen II drives, to replace after 3 seasons of use. Normally, they look fine when replaced, but since most of the expense is in the labor to open it up and check, why not put in a new one.
With older Merc drive, and engine driven pumps every other year, Volvo, every other year on any of their pumps.

 

[tkrfxr]

Re: Impeller replacement interval?

I have to agree with the every other year recommendation. The issue is the rubber...It deforms and wears inside the pump, and at some point, fatigue will cause break and failure....with pieces flowing through the cooling system and causing overheating...

I looked at my old impellers and they look just a little crooked...

 

[Don S]

Re: Impeller replacement interval?

I have to agree with the every other year recommendation. The issue is the rubber...It deforms and wears inside the pump, and at some point, fatigue will cause break and failure....with pieces flowing through the cooling system and causing overheating...

I looked at my old impellers and they look just a little crooked...

Never seen an Alpha Gen II impeller have you.

 

[tkrfxr]

Re: Impeller replacement interval?

Sorry, Don...

Never seen an impeller from an Alpha Gen-II drive...

What does it look like, say after 40-50 hours use?