Johnson RK-25D that runs great but will not go...

[dk012377]

We have a johnson RK-25D we are not sure of the year or the horsepower of this engine so if anyone knows that be great. Anyhow, we took out to the lake last weekend, this being the 1st run of the year, and it fired right up. The only problem is, it will not go. You can hit the throttle and giv eit gas and you can hear the engine rev up but the boat sits there. We thought the prop was not engaging but if you lift it a bit towards the top of the water you can see the prop is moving. We don't know where to start. My husband is a bit worried because he did not drain the gear oil before winter hit and he thinks maybe it may have froze and broke the shaft. Is that even possible? and if so wouldn't the prop not turn at all.

Anyone have any suggestions for us?

 

[tashasdaddy]

Re: Johnson RK-25D that runs great but will not go...

it's a 1963 40hp. hopefully i think that motor still had the shear pin for a drive pin in the prop. remove the prop, and there should be a about 1/4 diameter pin that goes thru the prop shaft that drives the propeller. have him check the drain plug on the lower unit for water, if it has water, after sitting the water will come out first, or the oil will look milky. regular maintainance parts can be found at laingsoutboards.com

 

[F_R]

Re: Johnson RK-25D that runs great but will not go...

If not the shear pin, maybe it has a spun prop hub. Getting more serious, that is an electric shift motor, right? Could be wiring or a bad shift switch in the control, or rusted parts in the lower unit if it was stored with water in it.

 

[dk012377]

Re: Johnson RK-25D that runs great but will not go...

Thanks for the ideas. How would we be able to tell if the prop hub is spun?

 

[F_R]

Re: Johnson RK-25D that runs great but will not go...

Make a mark on the prop nut (plastic cone) and a second mark on the propeller, aligned with the first. Run the motor till the slippage is experienced. Stop motor and see if the lines are still aligned. If not, the hub slipped. If they are still aligned, repeat test. There is a slim but unlikely chance that it stopped slipping in the same spot. Of course, this all assumes the drive pin isn't sheared, duh.

 

[dk012377]

Re: Johnson RK-25D that runs great but will not go...

Ok so the pin is ok and the hub has not slipped. We drained the old oil and it looked real good, no water in it at all but it only had maybe half of what it should have had in it. We refilled it and tested but that didn't cure the problem either We think maybe the shift switch could be bad but how would be able to tell? And where would we begin to look for a part like that? It is the orginal throttle so it's pretty old.

 

[F_R]

Re: Johnson RK-25D that runs great but will not go...

You need a voltmeter to check the shift switch. If you don't have one, you can get a cheapie at Wal-Mart. Remove the hood and at the rear of the motor, there is an electrical cable coming up from the lower unit. It has two rubber sleeves covering two disconect terminals. Slide the rubber sleeves back, exposing the terminals, but do not disconnect the terminals. Connect your voltmeter + lead to the green wire and the - lead to ground. Turn on the key and put control in forward gear. Voltmeter should read 12 volts. Not 9 or 10, but 12. Try shifting it a bunch of times. You should get 12 volts every time you put it in forward. If not, or if it is erratic, your shift switch or the wiring is shot. Do the same thing on the blue wire to check reverse. NEVER, under any circumstances allow the blue and green wires to contact each other when the motor is running!!!

Those switches are getting hard to find and the list price is over $400!! I have a new one if you are interested, but don't need $400 for it. Send me a PM.

 

[conkee1]

Re: Johnson RK-25D that runs great but will not go...

Hello F R I also own a RK-25D, really disappointed how slow the motor pushed the boat. The motor sounds good,just a full throttle i would think that motor should push that boat a little faster. Should i change props? thanks

 

[donsan]

Re: Johnson RK-25D that runs great but will not go...

Is it a short shaft motor on a 20in. transom? If so you need to have a long shaft installed.