1975 25 HP Timing

[OptsyEagle]

Re: 1975 25 HP Timing

It is always a good practice to do a compression test. Is it possible that the water is coming out of the water jacket near the head? If so, just try to tighten up the screws a little. If it is the head gasket, I would go ahead and get a new gasket and replace it. Again, I would like to know the compression numbers, before and after this change, just for reference.

I should add that on my 1975 15Hp motor, it idles down pretty good, but as I said, eventually it will shut down as I keep turning the grip clockwise. There is an idle adjust on the side of my motor that is supposed to limit this so it doesn't shut off, but mine doesn't work and I have never had a problem. I know where the RPMs are when it will die, I know when it is a good time to shift. So I don't really need the fast, start, shift and slow indicators either. In any event, if you have that knob on the portside of your motor you could try to adjust it so it doesn't shut off, if you prefer. Also, my motor will give a little shake and the occasional snort when idling. Many times even stall if I leave it to go get the fishing rod I forgot in the shed. Hey, it's a 38 year old motor. I give a few snorts and coughs when I wake up in the morning, these days as well. The main thing is that it never leaves me stranded and pins me to my seat at WOT. Those are really the only two important features for an outboard motor. The rest is really just cosmetic, if you ask me.

 

[series60]

Re: 1975 25 HP Timing

I also noticed that my head gasket was leaking water a little. Would poor compression cause these issues?

Water in the cylinder won't help the idle if the head gasket is leaking into the cylinder also. What is the compression on each cylinder?

 

[Richard911]

Re: 1975 25 HP Timing

I had broken that screw a few weeks ago and had forgotten about it. The screw limits how far you can turn the handle so I've definitly been turning it too far.

Secondly, I had to retap the plugs the other day. I just checked and saw oil around both plugs. I put the wrench on them and got another half turn out of them.

Lastly, with the carb synced so that the butterfly is closed but about to open between the two marks on the throttle cam, at wot in gear the butterfly can still open a little farther.

My neighbor at work is a boat mechanic. I'm thinking of asking him to do a compression test and see what the rpms are at idle.

 

[OptsyEagle]

Re: 1975 25 HP Timing

I had broken that screw a few weeks ago and had forgotten about it. The screw limits how far you can turn the handle so I've definitly been turning it too far.

Secondly, I had to retap the plugs the other day. I just checked and saw oil around both plugs. I put the wrench on them and got another half turn out of them.

Lastly, with the carb synced so that the butterfly is closed but about to open between the two marks on the throttle cam, at wot in gear the butterfly can still open a little farther.

My neighbor at work is a boat mechanic. I'm thinking of asking him to do a compression test and see what the rpms are at idle.

Great. A couple things. When you put the motor in gear I would imagine the butterfly will open a lot further at WOT, not just a little. I would imagine the butterfly is pretty much horizontal at WOT, in gear.

Lastly, be careful how tight you turn those spark plugs. The spark plugs probably have steel threads and the cylinder head will be aluminum so with the right wrench you could probably tighten them until they spin on there own, if you wanted to. Which you don't.

 

[Richard911]

Re: 1975 25 HP Timing

With the heli coils in now hopefully that won't be an issue.

At wot in gear the butterfly opens almost all the way.

 

[Richard911]

Re: 1975 25 HP Timing

My mechanic neighbor says my cylinders compress to 85 lbs. He also says he did a smoke test and my Crank shaft cover intake is leaking. He says this vacuum leak will cause the motor to not idle. I can see the gas and oil built where the two pieces come together too. He told me to use 1000 sand paper and lightly shave off a little metal from the crank shaft cover.

 

[OptsyEagle]

Re: 1975 25 HP Timing

Interesting coincidence. Is your motor doing this:

My Movie - YouTube

Taken from this recent thread.

http://forums.iboats.com/johnson-ev...5-hp-johnson-leaking-gas-its-side-591511.html

Maybe your problems are the same.

 

[Richard911]

Re: 1975 25 HP Timing

Yeah, that's it. We'll be doing the same thing. Thanks for pointing that out. Although my guy said not to try to seal it with anything and not to use form a gasket when putting it back together. He said there are little fuels lines that could get clogged.

He also said you could try to torc the bolts down with a torc wrench but I don't think that's going to work so I'm not going to try. At this point, I'm just debating on weather or not to buy a new crank case cover.

 

[steelespike]

Re: 1975 25 HP Timing

The indicators on the throttle handle are just reference points and don't necessarily correspond with actual throttle position.

 

[OptsyEagle]

Re: 1975 25 HP Timing

If you bought a new crank case cover, you would still need to seal it. It is probably just the seal so I would probably just re-seal it unless you can see a problem with it. Unfortuneately I have never re-sealed intake covers or crankcase halves or the like so I have to bow out on this one, but good luck to you. If you are going to re-seal, ask the experts here for what to use. I would imagine you would need something that takes a considerable amount of heat and is resistant to oil, gas and water. Not your average silicone if you follow my meaning.

 

[Richard911]

Re: 1975 25 HP Timing

I'm stuck. I removed the carb, armature plate and ring underneath it. I removed the eight bolts and two tapered pins around the crankcase. I removed the one bolt that goes in from underneath the power head and into the crankcase (intake side). I still cannot split the crank case. Where is the bolt that I'm missing? (No I haven't removed the powerhead)

 

[Richard911]

Re: 1975 25 HP Timing

 

[Joe Reeves]

Re: 1975 25 HP Timing

The powerhead must be removed in order to split the crankcase.

DO NOT "shave" any aluminum off of the crankcase as that will cause the crankshaft to seize between the two halves!

DO use a sealer on one side of the crankcase halves.... Sealer = Bombardier 3M Product #847.

(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.

 

[scanman]

Re: 1975 25 HP Timing

My '75 9.9 required the "gel seal" that Joe mentioned. I'd recommend Joe's instructions on this project, as he was instrumental in helping me with my rebuild last winter. When I finished it, I had about 90 PSI on each cylinder. The torque wrench will keep ya from stripping out the block halves upon re-assembly. Be sure not to remove the rod caps unless you are certain that it needs honing or rings, 'cause putting them back is a real PAIN! I'd also recommend getting a manual (from your local library?) so ya don't have to go back & forth to the computer.

 

[scanman]

Re: 1975 25 HP Timing

BTW, mine idles fine no matter how far I back the throttle off. It should only die when you hit the kill switch.

 

[Richard911]

Re: 1975 25 HP Timing

Busted a bolt flush trying to unscrew it. The driveshaft came out of the lower unit while taking off the power head. Too bad the crankcase wouldn't split without taking the powerhead off...


Edit:
I see now why the crankcase wouldn't split. There were two more bolts inside the chamber that houses the leaf (not sure the name).

 

[scanman]

Re: 1975 25 HP Timing

There are ways to remove a broken bolt, but you have to be careful not to damage the aluminum block & threads. We might be more help if ya post a pic of the broken one. Removing it kinda depends on how much of it is exposed. The drive shaft isn't a problem, though It'll need to be in the foot for the re-install. You should plan on a new water pump anyway, so that's easy. The "leafs" are the reed valves. I installed kevlar reeds, from Boysen, in mine before re-assembly. They provided more HP (approx 3%) & better fuel economy too! Ya might wanna look into 'em while ya have it torn down. If ya install 'em, you'll have to tune it a little different than what the book says, but for me, it was worth the trouble. When I got to the point where you are, I decided to do it all. I took EVERYTHING apart, cleaned all the gasket surfaces & water channels, replaced all the gaskets, etc. I shouldn't have to "split my block" again in my lifetime.

 

[Richard911]

Re: 1975 25 HP Timing

Any thoughts on how to get the driveshaft out of the powerhead? I've already taken a torch to it and it didn't budge.

 

[Joe Reeves]

Re: 1975 25 HP Timing

Have a friend helping you with this.

Have the unit horizontal preferably and have the driveshaft gripped in a vice on a non bearing surface, then using a block of wood and a good size hammer, tap the powerhead away from the driveshaft.

 

[Richard911]

Re: 1975 25 HP Timing

Had to beat the hell out of it, but it finally came out. We had some kind of pipe holder clamped down on the driveshaft. The pipe holder was secured to a post. We used a sledge hammer to beat a large socket that we had slid over the the drive shaft. it wouldn't budge until we took a torch to it and then started beating on it. Now I can start putting things back together.