Re: Newbie getting ready for the water again
You are dealing with the general boating public here!!!!!!!!!!!!!
EVERYONE AND EVERYBODY has/have their opinion(s) and their experiences. They usually report on them; I know I do.
"I" think 2 things help to determine the impeller replacement cycle. Sitting and operating in contaminated water.
Sitting: The impeller is a rubber wheel like you sometimes see at the top of a forum where it talks about parts, keyed to the drive shaft which connects the crankshaft to the prop shaft. The chamber where it rides is a centrifugal pump. For that kind of pump to work, a blade rotates through the water almost completely straight and as it rotates through 360 degrees, the chamber diameter decreases forcing the blade to bend at the tip, but also the volume decreases. This pressurizes the water and as the blade goes by the outlet port the pressurized water is forced up and into the engine. Pressure runs around 3 to 6 psig.
The problem occurs when the impeller is not rotated for long periods of time and especially where it is hot. It takes what I call a "set" whereby the blade retains the compressed configuration and when that part of it rotates past the starting point, it can't completely fill the area. This causes a loss of pressure at low rpms. It really doesn't matter at high rpms/water inlet ram pressures because the blades fold back and sort of just free wheel. In time this could lead to cracked and broken blades which could block your cooling path.
Again, the time it takes for this to happen varies. Some people have gone for 10-15 years with the same impeller. I boated most of my life without EVER changing an impeller on a lot of my engines and never regretted it.
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Contaminated water. Newer engines have the water pickup on the lower unit preceding the prop which is great for several reasons. On older OMC engines especially, the water pickup was directly behind the prop on the front of the exhaust deflector. This put all the sand and crud the prop picked up right into the inlet. Yes it had a screen on it, but the little grit and grime made it through. Over time this would wear out the water pump including the impeller.
Sooooo now you have the rest of the story. The decision is yours. I use my idle tell tale (pee stream) as an impeller condition indicator every time I go out. If my pee stream at idle is shooting into the water at least 1" below the surface, I am good to go. It usually goes more like 2" and I bought the boat in 2004 and haven't touched it since.
Additionally, engines today have over temp warning circuits that warn you if you have an over temp condition. I could add more but this is enough.
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Old gas: Again you are dealing with the general public. Personally, if I have old gas and I don't want to run it, I just siphon it out and put new in. Autozone sells a little red and black pump for about $15 that has hoses that you can run down and into the fuel tank and suck out the fuel. I use it to get the fuel flowing and then quickly pull the hose off and drain it into a container to be used in a lawnmower or other non critical functioning engines.
Fuel stabilizers are common and some use/believe in them and some don't. You aren't about to convince either side to change their colors so don't try. Just access the data and make you own decision.
My side: I joined this forum in 2006 as I recall and was introduced accidentally to Sea Foam. As the story goes this product was developed by someone working for OMC back in the '50's time frame and was desired to attack some engine problems they were having. The MSDS says that it is Naptha, Alcohol, and oil. Whatever it is, I keep it in my tank at the rate prescribed on the can: 1 oz per gallon of gas. I have not had to replace a fuel pump nor do any carburetor work since I have had the boat. The engine will run on the stuff so you don't have to be careful with it. On here are several articles entitled "Decarb" and derivatives of that title that walk you through a crash process of cleaning up your engine. It obviously works. Otherwise one could just dump a can of it (16 oz.) to a 6 gallon tank of gas and after running through that either use the 1 oz. per gallon or just eliminate it.
I had a weed eater and a chain saw that I thought were dead of old age. One day, having nothing to do, I experimented with SF and to my surprise they came to life and ran well enough for me to realize that the replacements that I had bought for these tools were actually unnecessary.
There is also a Startron product which I use in my farm diesels and it is also made for gas engines including OB's and also Stabil which has several varieties of treatment chemicals. I use Stabil in my small engines around the farm that may have fuel left in them for a year. SF is not marketed as a long term storage stabilizer, but it does.
All these products work for me.
HTH,
Mark
