Evinrude 135 impeller and housing R&D question

whoswho

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I am looking to replace my impeller and housing on my old 135 and got to thinking about the rubber impeller design that is used on pretty much all outboards. There must be a reason companies are still using the rubber impellers but has anyone heard of a water pump that does not fail so easily? I know some will say to simply not dry start it, but I have never dry started this engine. While doing some carb maintenance I hooked up the muffs and garden hose and ran it. Well the (replaced last year) impeller cooked itself. Here's my question: are rubber impellers the best they can do? It seems to me that a teflon vane pump, similar to a hydraulic vane pump with sliding vanes, would outlast the rubber vanes. There is no flex to speak of on the teflon vanes but that would not matter if the vanes are slung out by centrifugal force anyway. The only downside I can see is it ingesting crud and imbedding debris in the vanes and gouging the housing. Just a wonder going on but some of y'all may have more experience that me.
 

racerone

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I see it as an opportunity to make millions of dollars.---Go for it.
 

Fed

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OMC rubber impellers are very durable & work just fine until you do something wrong.
 

emdsapmgr

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The V6 and V4 impellers from OMC/Bombardier are some of the most durable in the industry. They literally last for years and years. When they get more than 5 years old, they don't pump the same pressure-but it's still enough to cool the powerhead. There must be some other factor responsible for your cooked impeller. Was the impeller housing deformed? Lower exhaust seal/grommet in place on the exhaust tube?
 
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F_R

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The Teflon vane idea is interesting. As far as other style pumps, nearly everything under the sun has been tried and abandoned in favor of the rubber impeller. BTW, if your 135 still has the aluminum pump housing, replace the complete water pump with the new kit that has a plastic housing with stainless steel liner. And never run it dry.
 

whoswho

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I am wondering if there was not enough water flow from the garden hose. The housing was plastic with the stainless liner too. Whole thing less than a year old. I must have screwed something up somewhere but after thinking about it there has to be a reason manufacturers still use rubber impellers. They must shed debris better or something.
 

racerone

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Agreed , many different manufacturers over the last 60 years and they all use rubber impellers.-------Note,---impellers are all " black " but they are not all the same.---Some designs are better than others.
 

emdsapmgr

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If you look at the V4/V6 Bombardier impellers, they have very robust fins, with extra buildup on the tips. Very durable. Merc uses this similar type in some of their V6 outboards and Mercruiser drives. On the other hand some of their low hp Optimax V6 impellers are small vaned and need to get replaced every 24 months. There is a significant difference between them, an not something you have any choice to control. Guess my question is why not make them all the more "durable" type?
 

whoswho

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If I get hold of a good pump housing it would be interesting to machine a vane hub and use different vane materials to do different tests. Delrin, PTFE and carbon impreg PTFE would be materials of choice. Maybe see how long they last under different scenarios. I know aircraft vacuum pumps are oilless carbon vane type pumps that have a 2000 hour TBO, but they have a filter on the intake so the air is pretty clean.
 

Faztbullet

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The reason they are rubber is $$$$$$$$ cheap to make and don't increase price of engine..
 

whoswho

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I have wondered about an electric powered marine pump that you can find at Harbor Freight. $35 and you can get the extended warranty plan. I do not know how much current draw they would have or what flow an engine needs. I have run those continuously on 12v and they did just fine for my application. You would have to find a way to tap into the existing pump discharge tube on the engine and you would have to make sure that your charging system worked or you could get caught with no way to keep the pump running. I have used my downriggers before and almost drained my main starting battery not knowing how much power they actually draw. A wind storm came up and I barely was able to get the engine started.
 

Fed

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I am wondering if there was not enough water flow from the garden hose.
You want the water overflowing out the sides of the muffs at all times, if the muffs are sucking themselves on then you're not supplying enough water. Pretty much fully open garden tap on a V4, too much can't hurt it.
 
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