Impeller replacement / waterpump service

[SkunkBoat]

Tell me about it they are crap.

Don't agree. Mine last 5 or 6 seasons easily. Can't say the same for my Mercs. To be fair though, my Yami impeller on my older 2 stroke is a lot larger in diameter than the Merc impellers and I think that the smaller diameter puts more strain on the vanes.
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The impeller isn't the problem, its the design & how it goes together...or doesn't....

 

[seasick]

Don't agree. Mine last 5 or 6 seasons easily. Can't say the same for my Mercs. To be fair though, my Yami impeller on my older 2 stroke is a lot larger in diameter than the Merc impellers and I think that the smaller diameter puts more strain on the vanes.

The impeller isn't the problem, its the design & how it goes together...or doesn't....
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Specific models?

 

[SkunkBoat]

The impeller isn't the problem, its the design & how it goes together...or doesn't....

Specific models?
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the one's we have been talking about with the plastic housing and metal cup and o-rings and spring washers and that plastic shaft bushing.
This thread is a perfect example of how you can put one together and the o-ring falls out and you never know...
and the plastic shaft bushing and spring washers jam and disintegrate...

They should stop "saving money" and make a metal housing with fewer parts.
I miss my old zuki 140.... housing, base plate, impellor, gasket, key...the housing lasted 12 years

Unfortunately, my new zukis will have plastic housing and metal cup....UUUGH!

 

[wspitler]

I have 2007 F250s and a2011 F150. The original impellers lasted 4 years (year round use in FL) and were fine when changed out for peace of mind My current set still going strong 925 hours total on two sets of water pumps. I like the design and the only challenge is getting the woodruff key out. I use thick silicone paste (grease) on all the o-rings and the impeller and it holds the o-rings in place while reassembling.

 

[seasick]

I have 2007 F250s and a2011 F150. The original impellers lasted 4 years (year round use in FL) and were fine when changed out for peace of mind My current set still going strong 925 hours total on two sets of water pumps. I like the design and the only challenge is getting the woodruff key out. I use thick silicone paste (grease) on all the o-rings and the impeller and it holds the o-rings in place while reassembling.

Same here. The woodruff key has always been a pain but I just use the dremmel trick and it works every time without damaging the drive shaft

 

[wrxhoon]

I'm glad you guys like them, I don't. Current engine F250 4.2 2013, impeller replaced before I got the boat 12 months ago by Yamaha dealer . Engine had 220 hours then.
The engine cools fine according to temp gauge however the tell tale has weak pressure. When I flush at home I block the side vents with tape put the muffs on for several minutes before I start the engine , still takes a minute to start peeing and after several minutes at idle speed the water is very hot , temp gauge still showing ok.
In my old 250 hp optimax I just put the muffs on ( no taping the big front intake or anything else ) start the engine and she would throw the water with heaps of pressure and never get hot just a bit warm. The merc had a proper temp gauge showing the degrees in C or F and the best gauge of all a water pressure gauge. 500 hours down the track still showing the same pressure no need to change impeller until you notice pressure drop. I have the upmarket MFD in my Yam but I still prefer the Merc Smartcraft. One thing I like in the Yam the digital control that my old Merc didn't have , I know the new V8's have though.
I will add that is for the 3.0 lt optimax 200 hp plus they have a bigger water pump than the smaller V6 engines that go up to 175 hp. These don't last more than 200-300 hours.
I don't know about the old supercharged Verados or new V8's .

 

[seasick]

The plumbing on the Optimax is very different than the Yami. On an Optimax, the water from the pump is split immediately into two flows. One goes up to the power head and the other goes through the air compressor and then directly out the telltale hole. The telltale water never touches the power unit. In a Yame is sort of the opposite. Water goes to the power unit and then goes both to the exhaust and the telltale ( with a little rerouting from the poppet valve depending on pressure..
A weak telltale on the Yami means poor water flow in the power head (assuming the telltale hose is not blocked) A weak or no telltale on an Optimax can be a really serious event but not necessarily to the powerhead. It can mean no water to the compressor and that can cause it to overheat. There is a separate compressor temperature sensor on the Optimax to keep an eye on temps.The compressor water feed for the Optimax has a filter on it also and that item is a maintenance task that should be checked if pee flow seems weaker than normal.
In any case, the telltale on an Optimaxwill normally start up a lot quicker than a Yami and also pee even before the motor is started.
The Yami telltale may or may not pee on muffs while the motor is not running; that depends on the water pressure and volume.

 

[wrxhoon]

Thanks for clarifying that makes sense . My Yamaha won't pee unless you start it I don't think but that's fine as long as it works and cools the engine . I think the Merc Opti runs colder as well, do you know if that is right? I still prefer the smartcraft .

 

[seasick]

The actual running temp is determined to a large extent by the thermostat specs. The Optimaxes can run hot at low speeds and cooler at higher but that is due to a few things: One is really crappy design of the cooling plumbing on earlier model Optimaxes. Some retrofit kits were made for certain models to address the cooling issues. In addition, the Optimax changes its combustion characteristics at low revs and that adds to the extra heating.
One important thing to be aware of is that the temperature of the telltale streamon the Yami is a decent measure of the powerhead water temps keeping in mind that one head on a V motor can be a lot cooler or hotter then the other but the telltale is the sum of both. On the Opti, the telltale temp is an indication of the temperature of the air compressor only. It is not by any means a good indication of powerhead temps.