Impeller, key, and baseplate issues

[gurugod1]

Had an issue just recently with my 1989 30 hp mariner impeller. To the best of my knowledge, my woodruff key got a little cockeyed during installation of water pump or was too large top to bottom, allowing for too much contact with base plate. Caused impeller to fail and upon further inspection I found a rather deep groove in the base plate. This metal on metal contact melted the inside of the impeller and the housing above the insert cup. The shaft was spinning around the inside of the impeller after the impeller was stripped, causing a plastic and rubber mess. Was tough to pinpoint how that happened, but I thought about the possibility of wrong parts from Sierra, like an impeller that was slightly too large, causing too much contact and wearing prematurely.

Turns out that the key being slightly out of place after sliding on impeller actually bent the wear plate after firing up the motor and using it for a few hours. In the future, I think I'll try to grind part of the key to avoid any contact with the base plate, allowing for the wp to work without any inadvertent heat oe friction issues after installation. Anybody ever heard of this issue before or know how to remedy?

 

[MH Hawker]

Re: Impeller, key, and baseplate issues

Sounds more like it was the wrong key in the first place.

 

[gurugod1]

Re: Impeller, key, and baseplate issues

I'm relatively new to the engine maintenance realm...anyone heard of getting wrong sized parts (keys, impellers, etc...) from sierra? I ordered a h2o pump kit and it seems as though both the key and the housing may have been a bit too large - just slightly different in size, enough to cause the pump housing to almost fit tightly, but not quite, and enough to allow the key to rub on and warp the base plate. I double-checked the order to make sure it was correct number and model. Are there better aftermarket choices that more closely meet the original specs?

 

[MH Hawker]

Re: Impeller, key, and baseplate issues

I try my best to get merc parts if I can, They are more expensive and I know sooner or later I will have to go after market. How ever over the years I have used a lot of sierra parts and never had any problems.

 

[gurugod1]

Re: Impeller, key, and baseplate issues

Put in new h2o pump today. Turned out I didn't take off the old gasket under the baseplate, raising everything just enough to grind with the impeller key, causing the heat and melting. Glad I noticed the gasket this time, I have to assume that was the problem - sure sounds like it was.

 

[MH Hawker]

Re: Impeller, key, and baseplate issues

It sure can be a lot of parts have some close tolerances.

 

[gurugod1]

Re: Impeller, key, and baseplate issues

New development...1989 30 hp Mariner motor runs fine, tell tale seems to work well, and does well on muffs in the driveway. Had it starting on one or two pulls after a carburetor rebuild. Like a champ on the muffs, so I took it down to the water this morning, couldn't get it started. Tried taking off silencer cover, engine started after several pulls, then put the silencer cover back on and engine died. Brought it back home, hooked up to muffs, ran like a top again, no problems, didn't have to take anything off. Took it back down to water, same no starting issue.

Seems that the back pressure from being submerged in the water is causing an issue here. I checked compression on both cylinders after 2nd attempt in the lake, both read 110ish, right where the manual says they should be.

I have a timing light, but no battery, as my motor is a pull start, so I'm hesitant to hook that up not knowing if I'd really need to. Any ideas as to what the issue may be? Here's a quick list of what I've replaced and checked recently (last 3 months):
- compression is good
- water pump is new (impeller, gaskets, housing, etc...)
- spark plugs are new, not fouled
- gas tank is new and properly vented
- primer bulb and fuel line are new, in correct position, and correct type
- carburetor cleaned and rebuilt, new gaskets, float, needle, etc...
- new pull rope on starter housing (not that this has anything to do with my issues)

I want to think it has something to do with timing, but I'm not sure why that wouldn't affect starting on the muffs. I also think that I could get into adjusting the float height in the carburetor bowl. My last thought would be the fuel pump diaphragm and gaskets, but I would think that this issue would affect performance on the muffs as well.