79 70 hp johnson impeller help

[Pipeliner542]

I have a new to me 1979 Johnson 70 hp It has been sitting for a while i changed out all the fuel hoses. cleaned carbs, new plugs, fuel pump, oiled and fired motor. it ran on muffs so i figured it was time to do lower. drained oil it was dark colored and dirty but no grit and no water. water pump had no grooves and no wear on the wear plate.(motor looks low hrs) I ordered a sierra water pump kit for it number 183387 my question would be, Is there a top and bottom to the impeller. one side has the brass bushing nearly flush with the impeller and the other is recessed a little. the recessed side has two xx marked on it. wondering which side went up. also when i took off the housing it didn't have a gasket between the wear plate and the lower assy. does the one with the kit get installed there. do you have to seal the lower assembly unit to the top with anything. it didn't have anything on it when i disassembled it my manual is on the way for this motor. for now any help would be great.

 

[Joe Reeves]

Re: 79 70 hp johnson impeller help

You say the impeller is recessed a little on one side.... the later model kits usually have a "O" Ring that sits in a recess of the impeller and that side with the "O" Ring faces up. You didn't say if a "O" Ring came with the kit that would be a size that would fit in that recess so I don't know if this is your case or not.

(Gasket Sealers)
(Usually available at any reliable automotive parts type store)
(J. Reeves)

Do Not use any type of sealer on outboard carburetor or intake manifold gaskets as this would cause blockage of various fuel/air passageways. Also, there are new type gaskets, including head gaskets, which are used through out the engines that are coated with a substance that gives a shinny appearance to them. These gaskets are coated with a self sealer and are to be installed as is.... no sealers! Older style head and fuel related gaskets that are not coated with this substance are to be simply coated with oil.... nothing else.

All other gaskets (hopefully I've not overlooked anything above) should be coated with Gasket Sealer (the type that comes in a can that has a small brush in its screw off cap). This also pertains to some water pump installations that use a gasket between the plate and the lower unit housing.

Marprox Sealer 1000 or OMC Adhesive or Boat Armor Sealer 1000 (same substance)[See Below Note] should be used on any metal to metal (Unless GelSeal Is Called For) or metal to plastic surface (such as impeller hsg to plate, and plate to lower unit surface) to eliminate air leaks. It should also be used on the Spaghetti tubing that is used on many powerhead crankcase halves, lower unit skegs, etc. I have found that this substance works quite well on various "O" Rings such as what are found on lower unit carrier and upper driveshaft bearing housings (Note that this substance is obviously not to be used on all "O" Rings). This substance also works quite well in sealing the surfaces between the lower unit and the exhaust housing to which it attaches, eliminating the unsightly water spray between the two after completing a water pump installation.

NOTE 1: I am under the impression that Marprox Sealer 1000 and Boat Armor Sealer 1000 is no longer available.

NOTE 2: OMC Adhesive is now Bombardier 3M Product #847 .

DO NOT use any sealer on the large "O" Rings that are used on the upper and lower crankcase heads (The housing/heads that slide over the top and bottom of the crankshaft). On those "O" Rings, use only a coating of grease.

The exception of surface to surface contacts pertains to the later model matching crankcase (block) halves (which does not incorporate spaghetti tubing) which call for "Gel-Seal", or any other surface that calls for Gel-Seal. This substance seals in the absense of air, and if called for, must be used. One other form of Gel Seal that can be substituted is "Loctite #518". Nothing else that I know of will do!

I advise against using silicone or permatex on a outboard engine. It simply will not function properly. The exception to this (as per OMC's recommendation), is to use the black Permatex (heavily) on the gasket 306242 which seperates the inner exhaust tube from the exhaust housing on the 1959 35hp and 1960 to 1970 40hp OMC outboards.

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

Wow. Thanks for all the info.

There was only one o ring in the kit. when I removed the lower it was located in a groove directly below the splines of the drive shaft. I found a Johnson dealer an hour from here that has the sealer ill go get some.

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

Opps... yes the o ring would fill the recess of the offset also it is the same size as the one removed from the drive shaft groove. there is only one in the kit.

should I install the gasket that came in the kit between the wear plate and lower unit. the diagram that i have from marineengine.com does not show the gasket under the wear plate.

 

[Joe Reeves]

Re: 79 70 hp johnson impeller help

I didn't want to rely on memory so I just looked in the OMC parts manual... There is no gasket used under the impeller plate on that model (1979 70hp). If the new plate is the same thickness as your old plate, I would say not to use the gasket but to use that sticky sealer between the plate and the lower unit.

If the new plate however is not as thick, then I would say to use the gasket (if it is indeed the proper gasket to go under that plate) and to use the Gasket Sealer substance on the gasket that is available at any automotive parts store etc. (Sealer that has a small brush attached to its screw on cap).

Since there is only one O Ring in the kit, that small O Ring is to be used in the groove just below the top splines of the driveshaft.

Whether a O Ring is designed to be atop that impeller or not..... Frankly I do not know. If it does not belong there, and you put one there, that may interfere with the pumps operation. Hopefully another member will jump in here that possesses that knowledge. If it were me, I'd not put one on top of that impeller unless I saw it installed in a parts diagram.

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

viewed several other dia. on line and a few youtube videos. None shown the gasket there either. plates are same thickness. im on my over to the boat shop to pic up some omc sealer. ill ask when i'm in there as well. do i apply a little marine grease on the shift shaft where it goes into the housing or is there some other lube for that. lower unit to case exhaust seal (big o ring?) any sealant or o ring lube?

 

[Joe Reeves]

Re: 79 70 hp johnson impeller help

It wouldn't hurt to apply some lubricant of some kind (any kind) to the shift rod in that area.

DO NOT turn the shift rod from its original position (up or down) the measurement is critical! Measurement is as follows, from the top surface of the lower unit to the center of the shift rod hole.

1978 - 1981 - 70, 75hp (L) 21-23/32" plus/minus 1/32". Have shift rod in neutral.

(1979 thru 1981 V/4 models = (L) 21-27/32" - - (XL) 26-27/32" Have shift rod in neutral)

Sealing lower unit to exhaust housing.... just apply a small bead of that sticky adhesive (Bombardier 3M Product #847).

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

is the measurement the same for the 3 cyl. i see you noted a v/4 its the 20" 3 cyl. I have never had it in the water now I feel I want to take it apart and check the rest of the work that had been done on the boat was pretty substandard. Makes me want to check. I know the person I bought it from said they had it apart but never had it in the water since they put it together. WELLL guess ill pull it back down to be safe

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

I dropped it back down It measured 21 29/32 from lower unit surface to center of bolt hole. ill adjust it. By the time the manual gets here It should be running.

Thanks for a great Forum and all the information

 

[Joe Reeves]

Re: 79 70 hp johnson impeller help

is the measurement the same for the 3 cyl. i see you noted a v/4 its the 20" 3 cyl. I have never had it in the water now I feel I want to take it apart and check the rest of the work that had been done on the boat was pretty substandard. Makes me want to check. I know the person I bought it from said they had it apart but never had it in the water since they put it together. WELLL guess ill pull it back down to be safe

Sorry... I meant to insert that one (below). Apparently I dropped down a line and copied the wrong one.

1978 - 1981 - 70, 75hp (L) 21-23/32" plus/minus 1/32". Have shift rod in neutral.

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

That is what I adjusted it to. It was off more than the 1/32". I checked it with three different tape measures all were within the 1/32 of each other so I assumed it needed adjustment. Why is the measurement so critical? And is there there anything that wears or causes that measurement to change and calls for readjustment?



putting batteries back in gonna put her on the water and see what happens

 

[Joe Reeves]

Re: 79 70 hp johnson impeller help

The measurement is critical simply due to the linkage setup. Once set properly, the measurement of that shift rod will never change due to wear, etc.

 

[Pipeliner542]

Re: 79 70 hp johnson impeller help

Well I put it in the water and the controls must be off now I figured something would have changed given the adjustment to the shift rod. I know the shift rod is set to the specs above. it will go into reverse but will jump out of gear in forward. when I disconnect the shift rod from the controls and manually put the lower in forward gear you can see it needs more travel to get to the forward engaged position. If you held control full travel forward it would engage but would never throttle up the motor. I didn't mess with it on the water. put it back on the trailer. Now the search for setting the correct position of the controls. will that be in the manual I ordered an oem Johnson service manual. Only question in my mind now is I wonder if everything worked before i adjusted the shift rod in the lower. I called the previous owner and he says he never put the boat in the water. Last registration on the boat was 2002 and he bought it in 2001 and never used it he said. he said it looked like it was setting when he bought it. He took it in trade for some money owed and parked it in the barn which is where it was covered in dust when I got it. One will never know well hopefully better luck this week.

 

[Joe Reeves]

Re: 79 70 hp johnson impeller help

(Centering Shift Cable)
(J. Reeves)

When all is as it should be, the proper method to adjust the shift cable is to disconnect the cable from the engine. Move the shift linkage on the engine to find the center of the play in neutral, and when found, leave it centered.

Now, grab the end of the shift cable sleeve, push and pull it to find the center of the play there, and center that play.

Adjust the trunion on the threaded portion of the shift cable so that the centered play of the cable lines up with the centered play of the engine's shift linkage. Install and lock the shift cable with the retaining clamp in that position. That's it.