Overheating Issue - SOLVED!!!

[Brentathon]

After trouble-shooting my high-rpm overheat for weeks ('91 5.7L Merc), I finally found out that it was the after-market Sierra brand impeller in my Alpha One drive (that I installed over the winter). The Sierra's impeller vanes have a significant set in them, and the rubber is much harder than the Mercury brand impeller that I took out of the drive over the winter (which had 2 seasons on it).
Has anyone noticed this with Sierra brand impellers???
This problem cost me about $700 and 12 hours of work. Not happy.
I feel like complaining to Sierra.........I guess they're part of Teleflex.

 

[sethjon]

Re: Overheating Issue - SOLVED!!!

It sounds like the wrong impeller was put in. Never heard of any problems with Sierra before.

 

[sltintexas]

Re: Overheating Issue - SOLVED!!!

I am not a genious..still trying to learn..but what do you think caused the problem with the sierra? Harder doesn't seem like it would be worse. If they spin it should circulate the water the same. I am not saying you are wrong cuz I flat don't know..just wondering...

What does this part mean

Sierra's impeller vanes have a significant set in them

 

[libellav15]

Re: Overheating Issue - SOLVED!!!

presumably its the set in them that is causing lack of efficiency from the impeller - water having somewhere else to sit rather than being 'forced' where its needed

good lesson for others - compare the old one to the new one (if it hasn't disintegrated that is!)

good info brent

Adam

 

[Brentathon]

Re: Overheating Issue - SOLVED!!!

I have a Alpha One Gen I, and I used the Sierra kit # 18-3517; is that wrong?
Aside from having a composite (i.e. fiberglass?) hub in lieu of Mercury brand's brass or bronze hub, the Sierra's impeller blades measure 0.100" less in diameter after 1/2 season, while my old Mercury brand had 2 full seasons. However, from being out of the boat for 2 days now, the vanes seem to be straightening up a little. The Sierra's rubber hardness (i.e. durometer) is definitely harder than the Mercury's; you can feel it when you bend the vanes. I'm wondering if the Sierra vanes failed to contact the casing (aka housing) completely around, or if the "set" (permanent deformation) in the vanes allowed for a slight gap, and thus reduced the flow a bit.

 

[MCL]

Re: Overheating Issue - SOLVED!!!

A bit offtopic but I think its wort telling.

Got a full rebuild kit from sierra.Both housings were bent and of very poor quality.Contacted sierra which told me to use it and check if it leaks.Well I dont want to blow up my new engine and decided not to use it.But the impeller looked ok,actually ended up using it.

So I bought a full kit from glm.Housings were also bent,but not as bad as the sierra ones.The impeller looked awful.Complained about this from the shop I bought it.

As a replacement I got marine engineering water pump.Never heard of them before,cant seem to find them online either.But the quality is impressive,actually thought I got oem merc parts before I checked the box.No idea about the price as I got it as a replacement.There was no impeller in the kit so I used the sierra one.I got a extra full kit waiting but I wont bother with changing the housings next time as these were such a nice piece.

All the parts was for a alpha one gen 1,pump with plastic housing.

 

[bigskiohio]

Re: Overheating Issue - SOLVED!!!

just installed a sierra kit installed easy and runs great

 

[Brentathon]

Re: Overheating Issue - SOLVED!!!

I just called Sierra and explained that there impeller appears to be defective; they want the invoices, and the guy said they may reimburse labor. Maybe I'll get some of the money back for this problem.

 

[Howard Sterndrive]

Re: Overheating Issue - SOLVED!!!

I know GLM reimbursed for customer labour when they had OMC impeller problems years ago.

good luck

they may have an issue with 1 supplier

that's the thing I notice with aftermarket... I recently ordered 2 hoses for something, and they shipped together in the same box... identical bags... parts inside were different... 1 was a Dayco hose, the other was quite different thickness and different rubber - no markings

these are "will fit" parts

 

[dsiekman]

Re: Overheating Issue - SOLVED!!!

I've been told by a mechanic buddy of mine that the vanes are supposed to be stiff. According to him, if you pull an impellor that is a couple seasons old, or has overheated, the vanes will be much softer than they are supposed to which in turn cuts down on how well they move water. Not sure if that is accurate, just what I've been told.

A couple years ago I had to replace one on the water on my 7.4 merc. Luckily I had kept the old one which was in good shape...never leave home without a spare and tools. I can tell you that it was a lot easier to squeeze into the housing than the new one was, so maybe he was right.

 

[Brentathon]

Re: Overheating Issue - SOLVED!!!

Yep, and everyone knows how critical an impeller is, in an Alpha One drive. Aside from dimensions, the elastomer material needs to have the correct physical properties, in order for the impeller to last and function properly. My theory, is that the material is too hard, and the vanes did not spring back open when they approached the wider section of the casing (aka housing), and therefore the pump output was lower at higher rpm's.
This could be a HUGE issue, depending on how many Sierra supplied like this. I ALMOST TOASTED my engine, because of this part.
DEFINITELY NOT HAPPY.

 

[Brentathon]

Re: Overheating Issue - SOLVED!!!

Just to update/correct this.............after sending back the impeller to Sierra, they determined that it was not theirs, and likely a Mercury impeller.
Therefore, someone put a mercury impeller into the Sierra pump kit that I bought from my marina, and the mercury impeller is from some unknown origin, which had a harder rubber, and the vanes took a considerable set (more than my old impeller did), and therefore, the pumping efficiency (flow/head) was reduced.

So.........it looks like I'm screwed.
At least I didn't toast the engine.

 

[zbnutcase]

Re: Overheating Issue - SOLVED!!!

I have installed many, many Sierra w/p kits and have never had a problem with them at all.

 

[Don S]

Re: Overheating Issue - SOLVED!!!

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