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Impeller for 1985 Johnson 4 HP deluxe

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souzag818

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Hello. I need to replace the impeller on a 1985 Johnson 4HP Deluxe with FNR. I can't get the lower leg where the impeller is apart from the rest of the OB. I've got a SELOC repair manual for it, but it's not coming apart like they say. Thoughts?
 
The shift rod should just slide out.------But if the motor has been neglected it is possible that the driveshaft is jammed in the crankshaft by RUST.----This can be a challenge for those encountering that for the first time.
 
souzag818 said:
Hello. I need to replace the impeller on a 1985 Johnson 4HP Deluxe with FNR. I can't get the lower leg where the impeller is apart from the rest of the OB. I've got a SELOC repair manual for it, but it's not coming apart like they say. Thoughts?
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You have removed all three bolts ?
I doubt very much if the shift rod is causing the problem like they suggest in the Seloc manual
Most likely the driveshaft is not coming free from the crankshaft due to being rusted in but if it is a long shaft model it could be that the drive shaft is not pulling through the bush in the extension.

If the latter may be the case simply take the extension off with the gearcase and then remove it after cleaning up the shaft.

However if it is the shaft rusted in to the crankshaft you will probably have to resort to brute force unless you can get some release oil in there and even then doubtful if it will work.

Brute force will eventually pull the driveshaft out of the pinion gear and through the pump BUT the impeller key will wreck the pump housing on the way so a that will have to be replaced. You will still have to get the shaft out of the crankshaft but once the shaft is free from the gearcas you will be able to remove the power head and get at the offending area directly

Ignore the warnings about having to dismantle the gear case to re-assemble if the shaft is pulled out of the pinion ... rubbish! but be careful the shaft does not damage the seals on its way back into position.
 
Last edited:
joereeves said:
What's the model number of that engine?
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Model Number is BJ4RDHCOB. Serial number is B005143.It says it was made in Belgium. None of the model numbers I've come across, including here, match exactly, but I've been able to get parts like the new impeller and a few other things matching up with Johnson model #J4RDHCDE. Thanks for the help
 
souzag818 said:
It is not a long shaft, and it does not have an internal fuel tank. Model Number is BJ4RDHCOB. Made in Belgium by OMC
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Your dealer should be able to supply the correct parts if you always quote the full model number. The dealer I use always asks for the model number even when I have looked up the parts numbers for parts I need.

Where abouts on the planet are you to have an engine with that model number? Somewhere in Europe ?
 
vics said:
You have removed all three bolts ?
I doubt very much if the shift rod is causing the problem like they suggest in the Seloc manual
Most likely the driveshaft is not coming free from the crankshaft due to being rusted in but if it is a long shaft model it could be that the drive shaft is not pulling through the bush in the extension.

If the latter may be the case simply take the extension off with the gearcase and then remove it after cleaning up the shaft.

However if it is the shaft rusted in to the crankshaft you will probably have to resort to brute force unless you can get some release oil in there and even then doubtful if it will work.

Brute force will eventually pull the driveshaft out of the pinion gear and through the pump BUT the impeller key will wreck the pump housing on the way so a that will have to be replaced. You will still have to get the shaft out of the crankshaft but once the shaft is free from the gearcas you will be able to remove the power head and get at the offending area directly

Ignore the warnings about having to dismantle the gear case to re-assemble if the shaft is pulled out of the pinion ... rubbish! but be careful the shaft does not damage the seals on its way back into position.
Click to expand...

I decided to put the motor upside down, on a stand, bracing it on the cavitation fins, and I can get a little less than 1/8" gap between the top section and the lower unit. I put a plastic wedge in there and sprayed the sh*t out of it with PB, hoping it will run down the shaft and shifter, and loosen up whatever is there- HOPEFULLY!! I'm gonna do this for a couple days and then tap on it with a hammer and see what happens. As long as I've had it (25-30 years) I've never changed the impeller and it's been a great motor...till now
u
 
vics said:
Your dealer should be able to supply the correct parts if you always quote the full model number. The dealer I use always asks for the model number even when I have looked up the parts numbers for parts I need.

Where abouts on the planet are you to have an engine with that model number? Somewhere in Europe ?
Click to expand...

LOL...No, Washington State. I bought it 25-30 years ago in Portland OR because it was a fresh water engine and it's been a great motor. I do remember awhile back trying to take it apart to replace the impeller, and i had the same problem as now, but it was pumping water fine so....if it ain't broke.........
 
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