Late '60s 6 hp cooling issue

[bassboy1]

I have been doing a little work on this late '60s 6 hp Johnson I picked up for a song. Because the motor is missing the ID plate, I only have the serial number to go by. Wbeaton and I have guessed it to be a 1968. If someone has a year list that goes into the 2.75 million serial numbers, I would appreciate if you could find the year for me.

Anyway, like all motors with unknown history, I check to see if there is gear lube, then hook up a fuel tank, and try to start it in a test tank. Once I sorted out the issues in the ignition (Flywheel woodruff key sheared, since flywheel wasn't torqued), I got the motor to run rough. I noticed that it wasn't pumping much water, and a short bit later, wasn't pumping any water. Wasn't real worried, as I figured the impeller was toast, and I wasn't going to kill the engine running it for 20 seconds. So, today, I put on a new impeller, and found the old one in pretty good condition, so it apparently wasn't the reason the thing wasn't spitting water. The sand in the water passages down under the impeller plate may have been the culprit.

Put it back together, and still no water, and it is starting to overheat. Great. Pull it back apart, expecting to find that I missed the water tube, or forgot the woodruff key, but all is well down at the water pump end. For kicks and giggles, I blew compressed air up the water tube, and a little sand popped out the exhaust hole (apparently this thing was run in very shallow water given all the dried sand I pulled out of the impeller housing, and water intake). I am fairly confident that at least by this point, I have gotten all the passages clear. Anyway, I bolt the lower end back on, again making sure I have the water tube lined up, and crank it again. No water again, after at least 15 seconds. So, I shut it off, and throw in the towel for the night.

Obviously, I am just leaving out one little detail, that I will probably kick myself for once y'all remind me of it, but I can't for the life of me figure out what I forgot to do this time. Also, what is the general consensus on how long it takes for water to start coming out of the exhaust ports on the exhaust housing? Obviously, some exits through the underwater exhaust, but eventually it will exit the top port too, and at a very good flow, at least based on my experience with other motors of this design. How long should that take?

Bassboy

 

[Zeeter]

Re: Late '60s 6 hp cooling issue

Ive seen clogs under the powerhead where the tube ends.

 

[tashasdaddy]

Re: Late '60s 6 hp cooling issue

pull the tstat. be really careful as the cover is very rare. i have the same motor, i actually had to take a drill and drill a hole in the tstat, inorder to pry it out. tstat is triangular cover on the rear top of the head. then flush heck out of it. i also had to ream out the water tube coming down inside the tstat housing. replace tstat cooling great now.

got it on a 1951 11 ft Feather Craft.

0310058 SEAL,Thermostat housing
0378065 THERMOSTAT
0311145 GASKET,Thermostat cap

 

[jay_merrill]

Re: Late '60s 6 hp cooling issue

Your motor should spit water as soon as you crank it up. There is a bypass in the water passages that allows flow, even when the t-stat is closed.

As you discovered, the area under the impeller base plate clogs easily. You have to clean it out thoroughly, and that includes the area behind the intake plate on the port side. This is another area where screws like to break, so be carefull. Make sure that the passage to the screened intake is clear too. If the screen is clogged, you will have to deal with that, as well.

Since you are going through this motor anyway, I would pull the head (its actually considered part of the tuneup procedure) to be sure that the water jacket is clear. You can replace the gasket upon reassembly. Once again, the possibility of breaking a bolt is there, so caution is the word! Don't forget to make sure that the tube that runs down the back of the head is clear - its part of the overall cooling system!

I usually don't pull exhaust covers unless I have to, because the bolts on them are among the ones that are most prone to breaking. Try all of the other stuff and see if it fixes the problem first.

Beyond just wanting to know, I wouldn't worry too much about the exact yeat of the motor, because there isn't much difference between any of the late sixties/early seventies, 6hp Johnsons. That said, if you want to post a few pics of it, I can probably tell just from that. Be sure to show the hood, the overall color of the motor and the decals/plates. I'll also want to see the latching mechanism on the back of the hood and cowl pan. You don't need a pic of it, but let me know if the cavitation plate is oval or rectangular, too.

 

[bassboy1]

Re: Late '60s 6 hp cooling issue

Been a little busy, (okay, try a lot busy), with my Eagle Scout Project, a buddies Eagle Scout Project, a customers boat, and a whole bunch of other mess, on top of school, so I haven't gotten back to y'all sooner.

Anyway, here are the pictures.

 

[bassboy1]

Re: Late '60s 6 hp cooling issue

And here is the problem. Lotsa sand stuck in the thermostat, and thermostat housing. Apparently, compressed air at 100 or so PSI could make it through, but water, at 8 PSI can't. Stupid me never thought about that.

 

[F_R]

Re: Late '60s 6 hp cooling issue

Year?? I think it is a parts box Heintz. The recoil starter is from the 1976-up era with a lockout which is missing. The lower unit with a round AV plate from an older one?? Light green paint under the hood suggests 1967-ish.

 

[jay_merrill]

Re: Late '60s 6 hp cooling issue

Your motor may be a hybrid - basically a motor that is built up from parts from various years.

The hood and lower cowl pan have the type of latch that was used in the 1968 motor and it has the rivet plate on the front, which was used to mount a Johnson "applique & plate." What the hood doesn't have, are port and starboard Johnson appliques, which mount via four pins each, that go through the hood. They may have been lost and the holes in the hood may have been filled, but if not, the hood isn't from a 1968.

If this is the case, I would say that the motor is older, because I don't believe the 1969 hood has the rivet plate. That hood used an applique that has the pins going through it on the front.

The paint color (Forest Green) is correct for a 1968 or 1969 motor, but that doesn't mean much because it could have been repainted. The older Johnson 6hp motors were all white - I just can't remember what year they went to Forest Green. I'm thinking that '67 was the last year for white.

The cavitation plate on your gearcase is oval, which makes it a 1965 or older unit. Although I can't see the prop and hub in your photos, if you have a rubber hub and your drive pin and cotter key are both on the aft end of the prop shaft, my presumption about the gearcase is correct. If the drive pin is at the forward part of the drive shaft and the hub is plastic, with a cotter key going through it, I'm stumped because I've never seen one of those with an oval cavitation plate.

As for putting a '65 gearcase on a '68 motor, we once had a long discussion about what fits and what doesn't in hybrid 6hp motors. Rather than to get into all of that, take a look at the following thread. At the bottom, I have a post with photos of a '65 Johnson 6hp that I own - notice the side view photo in which you can barely see the rivet plate like your hood, but look at the latch in the back too. It is a twist type latch on the hood, not a lever in the lower pan. My point is that, at a minimum, the pan and hood on your motor are not from a '65. They're from a newer engine, but maybe not a '68, given the side applique issue.


http://forums.iboats.com/showthread.php?t=232496&highlight=6hp+gearcase


Like I said before, the good news is that the parts for these motors didn't change much during the sixties and early seventies. You should be able to find the commonly needed stuff pretty easily. The exception to this will be the gearcase and associated parts. There is a spring load clutch in the '65 and older gearcases, that isn't included in the later models - see the above link. The parts for that clutch are NLA and you may have problems finding props too.

As long as you take care of the motor, however, it will probably serve you for a long time. They are great little engines and tend to be about as "bulletproof" as you will find in an outboard.

 

[samo_ott]

Re: Late '60s 6 hp cooling issue

One thing I haven't seen mentioned. Is the LU deep enough in the water? It's a common problem not to have it deep enough. Especially if in a pail or such. How are you testing it? Pail or on the boat in the water?

 

[jay_merrill]

Re: Late '60s 6 hp cooling issue

Given the amount of junk that you found in the t-stat housing, I would pull the head too. Once you have it off, clean every passage that you can get, both in the powerhead and the cylinder head, thoroughly. Don't forget the tube that runs down the back on the cylinder head.