Changing the prop and seal on a 1976 115hp

[oldguy60]

Hi there. I have a 1976 1150 thunderbolt engine and I need to replace the prop seal as I am getting water in the leg oil and the water pump seals (upper and lower) were just done with an impeller change along with new drain/fill plug gaskets and I can't think of anywhere else water could be getting in.

My question is: do I need any special tools to pull the prop and replace the prop shaft seal?

Also - is there any special tools or know how to replace the prop as I am planing to try several different props to get the best all round performance and I would like to be able to change them right at the lake if possible?

 

[daveswaves]

Re: Changing the prop and seal on a 1976 115hp

Hi there. I have a 1976 1150 thunderbolt engine and I need to replace the prop seal as I am getting water in the leg oil and the water pump seals (upper and lower) were just done with an impeller change along with new drain/fill plug gaskets and I can't think of anywhere else water could be getting in.

My question is: do I need any special tools to pull the prop and replace the prop shaft seal?

Also - is there any special tools or know how to replace the prop as I am planing to try several different props to get the best all round performance and I would like to be able to change them right at the lake if possible?

Changing the prop is easy you will need a "prop Wrench" available at your boating store or hear on I boats. The wrench is made of plastic and it floats.
Changing the seal in the lower end requires somewhat special tools to take the lower end apart and may be more than you want to tackle. A good winter project.

 

[oldguy60]

Re: Changing the prop and seal on a 1976 115hp

Thank you for your reply.
What about the other question - "is there anywhere else water could be entering the lower leg oil reservoir other than the water pump lower seal , the filler/drain plugs or the prop shaft seal" and seeing as I replaced the water pump seals upper and lower (when the impeller was done) and the drain plug seals then the only seal left is the prop seal??
Wouldn't it damage the transmission gears if I used it with water getting in the leg oil and I left it till winter (you mentioned it would be a good winter project)?
How long do you think a shop "should" take to replace the prop shaft seal?

 

[daveswaves]

Re: Changing the prop and seal on a 1976 115hp

Thank you for your reply.
What about the other question - "is there anywhere else water could be entering the lower leg oil reservoir other than the water pump lower seal , the filler/drain plugs or the prop shaft seal" and seeing as I replaced the water pump seals upper and lower (when the impeller was done) and the drain plug seals then the only seal left is the prop seal??
Wouldn't it damage the transmission gears if I used it with water getting in the leg oil and I left it till winter (you mentioned it would be a good winter project)?
How long do you think a shop "should" take to replace the prop shaft seal?

Other than a crack in the lower unit itself the only other seal is the large o ring that seals the bearing carrier to the housing. To replace this you need to pull the bearing carrier out. Is the oil milky or is the water running clear when you remove the lower drain plug?

Agreed, its not a good idea to leave the water in, however if the intrusion is small, you could change the oil and probably be OK till winter. In order to remove the bearing carrier you will have to remove the carrier retaining "nut" which is a large ring with slots in it. You cannot see this until you remove the prop. The ring is held in place by a metal tab which is sometimes hard to see, but it is there. The ring is often frozen in place and can be difficult to remove. A merc dealer will have a special wrench that is used to remove and replace this nut. If you are able to get the ring off using a punch and a hammer then you will need a slide hammer or special puller to pull the carrier out. If you wanted to change the seals and o rings yourself they are fairly straight forward. you could remove the lower end and take it to a merc dealer and have them remove the bearing carrier for you. This is one of those times when the tool is really necessary. I would think the hourly charge would be about an hour if they were willing to do it for you. If they do the whole job which should include a pressure test when done, likely 2 to 3 hours. Thats what it takes me, but I don,t work for money.

 

[oldguy60]

Re: Changing the prop and seal on a 1976 115hp

So this large O ring that seals the bearing carrier to the housing is not the same as what they refer to as the prop shaft seal (that's something different again)?
Like I said earlier I replaced the oil in the leg when I did the impeller and water pump kit and we took it out on the water for about 4 hours last Tues. and the next day I drained a small amount of oil from the leg and it looked milky so I drained it all out and replaced with fresh oil but there has to be a fairly conspicuous leak for it to get milky in just 4 hours in the water don't you think??
I don't beliveve there is any cracks in the housing that I can see.

 

[daveswaves]

Re: Changing the prop and seal on a 1976 115hp

So this large O ring that seals the bearing carrier to the housing is not the same as what they refer to as the prop shaft seal (that's something different again)?
Like I said earlier I replaced the oil in the leg when I did the impeller and water pump kit and we took it out on the water for about 4 hours last Tues. and the next day I drained a small amount of oil from the leg and it looked milky so I drained it all out and replaced with fresh oil but there has to be a fairly conspicuous leak for it to get milky in just 4 hours in the water don't you think??
I don't beliveve there is any cracks in the housing that I can see.

That is correct, the o ring is the diameter of the inside of the gear case, the prop seals(there are 2, stacked) are the diameter of the prop shaft. If all the oil you drained out looked consistantly milky you have a significant leak. If there was just a streak of milky oil in your drain pail it could have been residual water that was in your lower end when the water pump housing failed. A pressure test is the only way to tell without taking it all apart, that should be a relatively cheap procedure at your mechanics shop.

 

[oldguy60]

Re: Changing the prop and seal on a 1976 115hp

It was just streaky milky in color but I don't think the water pump housing failed (because I had the impeller and seals changed initially because I didn't know their condition as I had just purchased the boat and previous owner never changed the impeller) and when the impeller came out it was in fine shape but the impeller was changed and the twp seals (upper and lower) were changed at that time but the housing itself looked fine.
It's scheduled to go into the shop on Thurs. and I will get them to do a pressure test first as you suggest and go from there.

 

[oldguy60]

Re: Changing the prop and seal on a 1976 115hp

Well I have been at it two days now (trying to get a seized prop off the spline).
I am now at the point of chiseling the inner aluminum hub of the old prop off. I hope when I get through this last layer it does come off and is not welded on to the drive shaft through electrolysis like I have seen happen in aluminum heads where the spark plugs get welded because no anti-seize compound was used when they were installed.
Does anyone know if it's OK to pull on the "thrust hub" behind the prop with a set of pullers or is this not a good idea? I was thinking on using some pullers and heat to try and pull it off now that the outer hub. fins, and rubber is cut away and there is a channel chiseled into the inner hub??

 

[daveswaves]

Re: Changing the prop and seal on a 1976 115hp

Well I have been at it two days now (trying to get a seized prop off the spline).
I am now at the point of chiseling the inner aluminum hub of the old prop off. I hope when I get through this last layer it does come off and is not welded on to the drive shaft through electrolysis like I have seen happen in aluminum heads where the spark plugs get welded because no anti-seize compound was used when they were installed.
Does anyone know if it's OK to pull on the "thrust hub" behind the prop with a set of pullers or is this not a good idea? I was thinking on using some pullers and heat to try and pull it off now that the outer hub. fins, and rubber is cut away and there is a channel chiseled into the inner hub??

Boy that prop was stuck on, If you can get pullers in behind the thrust hub it wont hurt to pull on it. You could put it under tension with the puller and heat the inner aluminum hub till it pops. How did you make out with the leak test? If you are pulling it apart to change the seals anyway don,t worry about the heat. If you are not changing the seals you may damage the shaft seals with the heat. Sounds like you are changing the seals.

 

[oldguy60]

Re: Changing the prop and seal on a 1976 115hp

Well in discussion with my mechanic I have decided to forgo the prop shaft seals until I try it on the water again because when he looked at the amount of water/milkyness in the leg oil I had saved he figures it's a good possibility it was just left over moisture in the case from when the previous owner forgot to use a seal on the filler plug.

On the seized prop problem - I have finally got the old prop off but when I chiseled a groove into the inner hub I went too deep and also chiseled a small groove into two of the splines near the back end. I used some small files and filed them smooth again and the new prop slides on smoothly but I was wondering if vibration is going to be a problem or not because of this mishap??
My thinking is it will not because of the splined shaft being only 1" in diameter and it would not be as critical as a piece of a prop blade missing which would be 13" out from center?

When the weather clears up around here (weatherman calling for wind and rain for the next week) I will put it in the water and try it at WOT and see what happens and drain a little leg oil out afterward to check for water. I hope the new SS 13 1/4 x 17p "Ballistic" prop ( I bought on Ebay) is here by then to try or I will just go with the stock 13 x 17 Merc. prop it came with.

Thanks for all your advice!!

 

[oldguy60]

Re: Changing the prop and seal on a 1976 115hp

One other thing I forgot to ask - "how much torque should be on the prop nut" when installing a prop?
Should there be any play at all in the prop?
What i have been doing is to tighten the nut as much as possible (without over cranking it of course) and then backing it off just enough to line up the tabs on the tab washer?

 

[daveswaves]

Re: Changing the prop and seal on a 1976 115hp

Well in discussion with my mechanic I have decided to forgo the prop shaft seals until I try it on the water again because when he looked at the amount of water/milkyness in the leg oil I had saved he figures it's a good possibility it was just left over moisture in the case from when the previous owner forgot to use a seal on the filler plug.

On the seized prop problem - I have finally got the old prop off but when I chiseled a groove into the inner hub I went too deep and also chiseled a small groove into two of the splines near the back end. I used some small files and filed them smooth again and the new prop slides on smoothly but I was wondering if vibration is going to be a problem or not because of this mishap??
My thinking is it will not because of the splined shaft being only 1" in diameter and it would not be as critical as a piece of a prop blade missing which would be 13" out from center?

When the weather clears up around here (weatherman calling for wind and rain for the next week) I will put it in the water and try it at WOT and see what happens and drain a little leg oil out afterward to check for water. I hope the new SS 13 1/4 x 17p "Ballistic" prop ( I bought on Ebay) is here by then to try or I will just go with the stock 13 x 17 Merc. prop it came with.

Thanks for all your advice!!

You should be ok with the spline damage, don,t forget to grease the splines when you put the new prop on. When you get the new ballistic prop you may need a different thrust washer, can,t remember what the back side of a ballistic looks like.