Impeller replacement interval

[rkilpa]

OK guys.... For the last 7 years, my boat has been stored in a garage at Lake Havasu City, AZ where the temps top 120? for several months. Prior to Havasu, the boat spent most of its time in a garage in Southern CA and I could go 4 years on an impeller because the boat saw little use. I have found that I cannot go a full 2 years with about 50 hours on an impeller before it starts losing pieces of the tips of the vanes and I end up needing to fish them out of the thermostat housing. I have come to the conclusion that it is less effort to replace the impeller than to pull the TS housing so the last time I replaced it I swore to myself that I will change the impeller yearly from now on.

I usually just start the boat in the water after periods of non-use. I was thinking that the water in the housing might be evaporating when it sits for long periods without use in hi temps and I might be subjecting the pump to dry starts. I figured I could test my theory by hooking up the flushing adapter to start the boat in the driveway before going to the lake ensuring water was forced into the housing. When I lowered the drive to hook up the flushing adapter, water came out if the intake ports even after sitting for over a month indicating that there was still water in the intake lines.

This last year, the boat saw only 13 hours use instead of the usual 25-30.

My question is.... would you replace an impeller with 13 hours of use if it is only a year old but was exposed to high temperatures for extended time? Although it's less effort than pulling a TS housing, it's still a pain-in-the-butt to do.

 

[GA_Boater]

First thing is you shouldn't be storing with the drive up. It should be down.

Second thing is with the drive up, a small amount of water will puddle in the front of the impeller and pump housing, so it's no surprise that some water appeared.

Third thing, there is no way you are doing dry starts with the drive lowered into the water.

Fourth thing, you've identified the cause, heat. In your case, annual impeller replacement may be the only fix.

 

[wrench 3]

I agree with storing with the drive down to extend bellows life, but doesn't his unit have the raw water pump high and dry on the front of the engine?
rkilpa: I think the only way your going to know is to pull the impeller out and inspect it. That won't help much this time but you'll know for next time.

 

[GA_Boater]

I agree with storing with the drive down to extend bellows life, but doesn't his unit have the raw water pump high and dry on the front of the engine?
rkilpa: I think the only way your going to know is to pull the impeller out and inspect it. That won't help much this time but you'll know for next time.

Yeah - Not Mercruiser with the impeller in the drive. Shucks!

 

[bruceb58]

I agree with storing with the drive down to extend bellows life, but doesn't his unit have the raw water pump high and dry on the front of the engine?

When the boat is in the water, the pump on the front of the engine is actually lower than the water level so there is water there almost immediately.

I change my Volvo impeller every 2 years. I only use OEM Volvo impellers.

 

[rkilpa]

I replace my impellers with only OEM Volvo impellers as well. If I were to go through the effort of inspecting the impeller, I would just replace it. The frustrating part for me is the access to remove the hoses so I can remove the pump housing from the bracket. Once the housing is off, replacing the impeller is fairly painless. The boat is small and the access to the intake pump and the oil filter make for awkward body positions even with the engine cover removed.

I had already purchased the new impeller with all my year-end service supplies, but when I checked the hour meter and saw only 13 hours elapsed from the last change, I didn't think it would be necessary. I remembered that every time I replaced the impeller in the past, even after it sat unused for months, what seems like a gallon of water would come out of the hoses attached to the pump housing, so I know my concern about dry starts was unfounded.

I know I should have just done it since I had the part, but I'm trying to justify to myself why I didn't do it. I anticipate a similar low hours year this upcoming season. I will have no one else to blame if I can't get 2 years out of this one with what I expect to be about 30 hours total on an impeller that is supposed to last 100 hours.

 

[Scott Danforth]

impeller age is not hours of use, however hours since it was pulled out of the molding machine. things like running them dry or excessive heat prematurely age them. even if you put a new impeller in the boat, let it sit for 5 years and never ran it, you should change the impeller.

I change my impeller every 18-24 months. Based on your location, heat, etc, I would recommend you change your impeller every year (its like a 10 minute job on Volvo Penta motors)

store your drive down for your bellows. your impeller doesnt care where the drive is stored.

 

[bajaunderground]

If you're losing an impeller a year given the parameters, I would pull the whole pump assembly and inspect the inside for corrosion and maybe a burr. I replaced risers, fuel pump assembly, thermostat and impeller chasing an over-heating issue...turned out to be the raw water pump housing had a large burr on the inlet/outlet opening which was eating my newly installed impeller which in turn sent little pieces into my thermostat housing and occluded my by-pass which cools the fuel pump (or is supposed to)...so wasn't a "running dry" issue or to hot, but the impeller was compromised almost immediately. I replaced the housing and put 80 hours on without one incident of overheating.

While these motors and accessories are simply in nature, one little hiccup can take forever to trouble shoot and find what the root cause is?

At the very least keep a spare on board and the required tools to replace it! Keep in mind that if you pull the inlet hose, be ready to plug it off while replacing impeller, otherwise you'll fill up quickly!

 

[Thalasso]

Air temps aren't going to effect the impellers. Are you using OEM stuff? Mine get changed every 2-3 years.
Drive up in the driveway is ok. Won't hurt a thing. Storing for long periods like the winter is no good though

 

[bruceb58]

The only time my drive is up is while I am towing or I am beached. ALL other times it is down.