56 Johnson 30 horse - impellor keeps going out

[sdoomaha]

1956 Johnson long shaft 30 horse. Have replaced the impellor 3 times in the last 30 days. The metal center of the impellor keeps twisting loose from the actual rubber impellor. Thought it was using aftermarket impellor, but used OEM last 2 times. Only got about 20 minutes of use from the last one before it "twisted out."

Thoughts? do I need to replace the entire housing and plate? They don't look bad or feel like they are grooved up..but I am at a loss....and am getting tired of getting back to shore using the trolling motor. On an old 1977 Kayak 24 ft pontoon boat. Boat stays in the lake so lower unit always remains submerged so I know it isn't due to running it without water. Any input / direction appreciated.

Steve O!

 

[JB]

Re: 56 Johnson 30 horse - impellor keeps going out

I would replace the whole thing, Steve. The housing may be warped. I also use a bit of Vaseline on the impeller before installation.

Be sure to NEVER crank the engine with a dry water pump.

 

[F_R]

Re: 56 Johnson 30 horse - impellor keeps going out

Tilt it out of the water when not being used. I was told by an OMC engineer that was caused by electrolysis. Yeah, I know, I didn't believe it either. But the problem seems to have gone away when they started using plastic pump housings.

Probably too quick for electrolysis to happen, but just the same......can't hurt to tilt it.

 

[HighTrim]

Re: 56 Johnson 30 horse - impellor keeps going out

Something must be severely warped. You would think that if it was warped enought to tear apart the impeller the housing bolts would no longer line up. Strange, Im stumped.

Silly question, but what part number are you using? Are you reusing the same key evert time? What is the condition of the shaft where the impeller rides, is it severely worn, causing the impeller to wobble underway? Same with the plate, is is severely grooved?

 

[sdoomaha]

Re: 56 Johnson 30 horse - impellor keeps going out

Thanks all!

Motor was never even cranked dry...was mounted to boat and submerged before trying to start.

Thans for suggestion, will "tilt" between uses.

The pump housing is "oval shaped" IE the impellor is not centered in the housing...but the hole the shaft rides through is perfectly round, so I assumed it was supposed to be that way.

Water pump housing screws line up perfectly. Part number is 375808, which per the website was replaced by 0775521 OEM which is what the last 2 installed were. The key is the key that came with the shaft. The shaft is in great shape...fairly new shaft as we changed it from a short shaft to a long shaft last summer. Did have to "move" the key down on the shaft (drilled new hole to insert the key) but there is "play" with the width of the impellor so that we know the key is riding within the impellor center. The plate has some "wear" but I would not call it grooved.

Hate to drop the $100+ to replace the housing and plate...but not sure what else to do....I guess it is time to move to "throwing parts at it" and hope we find the correct combination to cure the issue.

I know...it's a 56....but that is the charm of it....lots of folks around the lake get a kick out of it...and brings back memories to some, so I hate to give up on the motor.

Thanks again all....all input is tremendously appreciated!

Steve O!

 

[nwcove]

Re: 56 Johnson 30 horse - impellor keeps going out

"oval shaped" could be an issue. but why is it oval shaped is the question.

 

[HighTrim]

Re: 56 Johnson 30 horse - impellor keeps going out

I think he is just referring to the fact that it is eccentric, off center pump, which is normal.

So some more info comes out now, lol.

Im going to guess that your new drilling of the key hole is a factor in this, mainly that it may not be centered on the width of the impellor, causing it to wobble. Im still not sure why this was necessary, what shaft did you use?

 

[nwcove]

Re: 56 Johnson 30 horse - impellor keeps going out

i was picturing an "egg shaped" housing, thought it may have been a victim of ice. i agree with hightrim tho, there should have been no reason to modify the driveshaft if it was the right part. find the right shaft before you spend $$ in the wrong direction.

 

[Chinewalker]

Re: 56 Johnson 30 horse - impellor keeps going out

I think I know what's going on... you've got the wrong driveshaft. Only reason you would have had to move the impeller drive pin is because it is from a different model motor. What I suspect is going on is that the driveshaft is a hair too short and is not fully seated, either in the lower unit or the crankshaft, such that it is riding up or down as the motor runs, and with positive pressure on the impeller it is pulling and pushing on the hub, thus twisting the vanes off...

 

[cajuncook1]

Re: 56 Johnson 30 horse - impellor keeps going out

I think Chinewalker hit the nail on the head!!!


You can try posting a free Webvertise WTB (want to buy) ad at the AOMCI (Anitque Outboard Motor Club Inc) website. A lot members have spare parts, motors, and parts motors. Salvage yards often troll through the ads for prospective buys.

Here is the link to AOMCI Webvertise. Please read the 1st link for the rules and 2nd link is the link for the actual posting.

http://www.aomci.org/cgi-bin/yabb2/YaBB.pl?num=1326461963

http://www.aomci.org/cgi-bin/yabb2/YaBB.pl?board=Webvertize


Here is a bunch of links to online salvage yards around the United States.


http://www.sea-way.com
http://www.outboard-parts.com
http://www.laingsoutboards.com
http://www.tcoutboard.com
http://www.fairwindsmarina.com
http://www.salvagemarine.com
http://www.marinepartsoutlet.com
http://www.outboardexchange.com
http://www.Superior Marine (800-338-9281)
http://www.budgetboats.net
http://www.americanoutboard.com
http://www.piratemarinesalvage.com
http://www.trixieslanding.com
http://www.mmmarinesalvage.com

Good luck!!

 

[nwcove]

Re: 56 Johnson 30 horse - impellor keeps going out

........or could it be the original long driveshaft, cut and welded, in an attempt to save a few bucks?

 

[Tim Frank]

Re: 56 Johnson 30 horse - impeller keeps going out

Re: 56 Johnson 30 horse - impeller keeps going out

Water pump housing screws line up perfectly. Part number is 375808, which per the website was replaced by 0775521 OEM which is what the last 2 installed were. The key is the key that came with the shaft. The shaft is in great shape...fairly new shaft as we changed it from a short shaft to a long shaft last summer. Did have to "move" the key down on the shaft (drilled new hole to insert the key) but there is "play" with the width of the impellor so that we know the key is riding within the impellor center. The plate has some "wear" but I would not call it grooved.

Can't imagine any reason that you should be drilling a hole in the driveshaft. It is either the right part or not.
That drilling operation is critical, and not easy. I am a "reasonably" competent amateur home shop machinist, and I'd probably get a pro to do that job.
If you don't get that hole dead nuts through the c/l of the shaft, you are introducing eccentric forces that may be the source of your problem.
My vote is the d/s mod.

Hate to drop the $100+ to replace the housing and plate...but not sure what else to do....I guess it is time to move to "throwing parts at it" and hope we find the correct combination to cure the issue.

If you have changed the impeller three times in a month, you are already there.... :facepalm:

 

[sdoomaha]

Re: 56 Johnson 30 horse - impeller keeps going out

Re: 56 Johnson 30 horse - impeller keeps going out

Sorry for delay in response...was traveling for work. Got parts off ebay to extend from short shaft to long shaft. Drilled a hole in the driveshaft to "move" the key for the impellor down....had to move it down about 3 inches. Sorry for not sharing all info up front...didn't think it would be an issue as long as the key was within the slot of the impellor. So will ck the websites provided to see if I can locate the "proper" shaft. That sucks since I already have $75 in the one installed. Oh well....live and learn.....

THANKS AGAIN TO ALL FOR THE INPUT!! TRULY APPRECIATED!

 

[oldybutagoody]

Re: 56 Johnson 30 horse - impeller keeps going out

Re: 56 Johnson 30 horse - impeller keeps going out

I agree with all the comments about the pin needing to be centered but JB's comment about lubing it with Vaseline shouldn't be lost. If the pump is dry, it wouldn't take much to make the rubber heat up and fail. Have you checked that water pickup and passage up to the water pump housing isn't plugged? That would make the pump run dry.

 

[sdoomaha]

Re: 56 Johnson 30 horse - impeller keeps going out

Re: 56 Johnson 30 horse - impeller keeps going out

YUP!

Last time installed used regular automotive grease...will use vaseline this time around. Passages are clear and free...blew compressed air through them to make sure...but thanks again for the input. Looks like concensus is the key driving the pump may not be perfectly centered causing it to not run "true." Well...since I got the new housing and plate...and I have a spare impellor...gonna try it one last time before I search out a new drive shaft. I know I know....I'll get what I deserve....but hey...nothing ventured nothing gained.

Thanks again to all who took their time to respond and get me going in the right direction.

TRULY APPRECIATED!

 

[Tim Frank]

Re: 56 Johnson 30 horse - impeller keeps going out

Re: 56 Johnson 30 horse - impeller keeps going out

Good luck, let us know how it works out.
BTW, use the grease again so that if it happens to work,that the vaseline does not get the credit. Nothing wrong with the vaseline, but nothing wrong with the grease either....