1974 rude 50... paraniod or problem?

Okay so this saturday is the splash date for my starcraft project, and hung off the back is a 74 rude 50 that i picked up almost a month ago. a little background on the motor, i traded a non running 69 johnson 55 for it. when i did the trade, it was on a boat at the time, and he took me for a ride and it performed well. it starts right up, like 1 spin and its running. after warming up it doesnt even have to be choked to start.


so yesterday i decided to do a decarb on it. things were good for the first 3 or 4 times i ran it. the last time it seemed to be a little on the hot side, i couldnt hold my finger to the powerhead for more than 2-3 seconds. when i shut it off, for about 20-30 seconds after there was this thin white smoke coming out of the exaust, didnt look like typical 2 stroke.

with no tell tale, i wasnt sure what the water pressure was like. but i do know that there was water rolling out of the exaust after i shut it off, also there was water coming out the vents on the sides of the LU and also coming out the rear of the lower unit there is a hole that had water coming out at a pretty good pressure when it was running.

i tried to test the overheat alarm, but dont know if i was doing it right. i disconnected one of the yellow wires that comes from the back of the buzzer, disconnected it from the bus bar right next to it and with the key on touched that wire to a bolt on the engine block. nothing. what else can i do to troubleshoot?

am i paranoid or is there a problem? im leaving for vacation next week and am going to replace the impellar when i get back, but i just want to get out at least once with it!!!

Re: 1974 rude 50... paraniod or problem?

Tan lead from temp sensor touched to ground will test horn. White may be steam (and you may have an overheat). When was water pump last done? I'd be inclined to replace entire pump with a complete pump kit. BRP kits used to have instructions packed with them.

Re: 1974 rude 50... paraniod or problem?

wilde1j said:

Tan lead from temp sensor touched to ground will test horn.

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where is the temp sensor???

Re: 1974 rude 50... paraniod or problem?

Upper aft part of block. Looks kind of like a black plug with a slide on terminal on it.

Re: 1974 rude 50... paraniod or problem?

heres a pic of the sensor location off my '75 Rude 50. should be same or similar on yours. The tan wire is for the sensor. the black goop is covering the knife terminals, you should have a black sleeve covering yours, just disconnect the controls side, and ground it, you should then hear the buzzer.


The black rubber hose and brass fitting in the back of the head cover is my homemade pee stream indicator. No more questions about whether the water pump is working for me

Re: 1974 rude 50... paraniod or problem?

InvaderScott said:

heres a pic of the sensor location off my '75 Rude 50. should be same or similar on yours. The tan wire is for the sensor. the black goop is covering the knife terminals, you should have a black sleeve covering yours, just disconnect the controls side, and ground it, you should then hear the buzzer.

The black rubber hose and brass fitting in the back of the head cover is my homemade pee stream indicator. No more questions about whether the water pump is working for me

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thanks! how did you put in the pee hole? can you just drill it anywhere? what size fitting did you use?

Re: 1974 rude 50... paraniod or problem?

I had the cover off to do the thermostat, so I drilled it in an area where there is no "structure" underneath, just water jacket. I then threaded the hole for an 1/8NPT hose barb, added some 7/64ths vacuum line, and placed another fitting in the bottom of the housing where I could see it.

Re: 1974 rude 50... paraniod or problem?

InvaderScott said:

I had the cover off to do the thermostat, so I drilled it in an area where there is no "structure" underneath, just water jacket. I then threaded the hole for an 1/8NPT hose barb, added some 7/64ths vacuum line, and placed another fitting in the bottom of the housing where I could see it.

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i would assume i need a thread tap for the hole?

Re: 1974 rude 50... paraniod or problem?

yes, you will need to tap the hole for threads.

Re: 1974 rude 50... paraniod or problem?

okay, 2 more questions. what size tap, and is there a gasket under the cover and if so is it reusable or will i have to replace it?

Re: 1974 rude 50... paraniod or problem?

no worries, yes there is a gasket under the cover, NO it most likely will not be reusable. I had to scrape mine off with extreme predjudice. Use this as a good opportunity to change the thermostat while you have the cover off (thats why I originally pulled mine). Tap size needed is 1/8 NPT. any good hardware store should carry this size. (pipe threads are tapered so you get a seal, Its a specialty type tap, but a good store should carry it, they are very common)

As for the other side of the tube, I just took a double hose barb (hose mender fitting) and filed off one side of the barbs (I chucked it in my drill, and while it was spinning, hit it with the file), to get a smaller diameter, and a shoulder to mount against. I then "glued" it in the hole I drilled in the lower housing with some 5200. Looks good, cheap, and effective (total cost involved, about 10 bucks)

Re: 1974 rude 50... paraniod or problem?

Andy, I'm concerned about you possibly grenading this thing on your maiden voyage. Make sure you are able to either test your overheat horn or figure out some other kind of temp system (melt sticks maybe?). I'm no expert by any means but I just don't want to see you kill your new motor because something's up with the water pump or thermostats.

Re: 1974 rude 50... paraniod or problem?

ezmobee said:

Andy, I'm concerned about you possibly grenading this thing on your maiden voyage. Make sure you are able to either test your overheat horn or figure out some other kind of temp system (melt sticks maybe?). I'm no expert by any means but I just don't want to see you kill your new motor because something's up with the water pump or thermostats.

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i know believe me ts not going out unless i think its 100%. im going to test the horn in a few min here, and if its not working then no dice. i'll wait till after i can change the impellar.


so that brings me back to an earlier question... there is a stream that seems to be under pressure from the very back (front? opposite side of the prop). is that any type of indication that the impellar is working? it seems like its pretty high pressure... it sprays right against the transom.

Re: 1974 rude 50... paraniod or problem?

I assume you're on muffs. Problem with those is they can force water through the block to some extent thus not really telling you if your pump is working. That stream your talking about might be just from your garden hose forcing water though. You could always go the big bucket method and see if it overheats. Make sure you submerge it far enough. I tried it once and did NOT have it submerged enough and ended up taking it to the shop for nothing.

Re: 1974 rude 50... paraniod or problem?

Very easy to tell if it's overheating. Let it run on the hose for about 5 min. If the heads are too hot to touch, it's overheating. Motor should run ~ 150? F or lower, which is cool enough so you can touch for a while w/o getting burned. No melt stick or IR gun needed!

Re: 1974 rude 50... paraniod or problem?

well, the overheat buzzer works... is there any way to test the temp sensor?

by the way, heres a video of how easily it starts...

Re: 1974 rude 50... paraniod or problem?

Daaaayum Andy, I wish mine started that easy.......


Only way I know of to test the sensor would be to remove it, and stick it in appropriate temp water and see when the resistance drops to ~0 ohms.

Either that or you can overtemp the motor, but I wouldnt reccomend that......

Re: 1974 rude 50... paraniod or problem?

Don't remove it ... a crude, simple test: disconnect the tan lead and measure the resistance from the sensor to ground. If zero, it's clearly bad and replace it.
More elegant test: remove the sensor, put in a pot of heated water and measure the temp @ which the switch closes. I'm guessing it should be ~ 200? F, but my engines (E-Tec) use an entirely different type of sensor.

Re: 1974 rude 50... paraniod or problem?

You should be able to relieve most of your paranoia by servicing the water pump. Better yet, install a pisser tube and you'll really be able to sleep well at night.

Re: 1974 rude 50... paraniod or problem?

McGR said:

You should be able to relieve most of your paranoia by servicing the water pump. Better yet, install a pisser tube and you'll really be able to sleep well at night.

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I plan to do that. but the problem is ive been looking forward to tomorrows splash date for what seems like sooooo long, i just want to get it out there and run it! i would need to order parts of the internet, or drive 2 hours to get them. im headed out on vacation next week... (not bringing the boat) but there will be marinas and marine part suppliers near where i will be, and i am planning on picking up the parts while there so i can do it when i get back. i just need peace of mind that i can take this out for a 30min to 1 hour shakedown cruise.



what are the odds that the temp sensor could be bad?