Watermann
Starmada Splash of the Year 2014
- Joined
- Jan 12, 2013
- Messages
- 13,822
On my Sea Nymph restoration I was on the last leg of my motor refresh and down to putting the oil in the lower unit. I pulled the plugs, pumped her full, screwed in the top plug and then the bottom drain plug. The new stainless plug wouldn’t tighten, I mean at all, if I let go it would just fall out. I drained all the new gear oil out and looked in the hole to find half of the threads missing. So here is what I did.
My motor is a 1977 Johnson 55 horse and uses 3/8” drain plugs with 16 TPI. (Threads per Inch) Be sure to find out the correct size and TPI for your motor.
Auto parts house for a 3/8 16 TPI Heli-coil kit that comes with coils, coil driver tool and the tap. (Expect to spend $20-25) The package will tell you what size drill bit you need for the job, mine was a 25/64th.
Next step was to drill out the drain hole in the lower unit. None of us wants a bunch of metal shavings inside our lower unit with all the gears and bearings. I used a shop vac held next to the hole as I drilled. Recruit someone to help or strap the hose on the unit so you can use both hands on the drill.
Ready now to tap the hole out with new threads for the heli-coil. Smear the grooves of the tap with bearing grease to catch the chips as the tap cuts. I did mine twice, cut threads in half way, backed out the tap, got rid of the chips and then reapplied clean grease to cut the remainder of the threads.
Now take your drain plug and screw it into the heli-coil without the washer gasket on the plug. Count how many coils you have extra on the coil. Remove the plug and cut those coils off with some sharp side cutters. (Don’t cut off the drive tang from the other end). Mine needed 3 coils cut from the heli-coil so it would fit. When you drive the coil into it’s new threads, you want none of the coil to stick out from the hole or your plug washer gasket won’t seal.
Coat the coil with thread locker, I used the blue just in case it needs to come back out. The coil should drive in easily and start to get a little tight towards the end. I left the heli-coil drive tang on mine rather than take the chance of breaking it off and having it fall inside the lower unit.
To be sure to have all the shavings and chips out, I rinsed the lower unit out with the milky mineral spirits using my lower unit gear oil pump. I put the hose in the top vent hole and pumped the spirits in, allowing it to run out the drain. This flushed out all of the older particles and more of the fresh shavings from the tap job. I then used my air and blew air in form the top until nothing came out the bottom, just to get all the spirits out.
Refill lower unit with fresh oil, put your drain plug in it’s nice new steel threads.
Hope this little tutorial helps someone in the future.
My motor is a 1977 Johnson 55 horse and uses 3/8” drain plugs with 16 TPI. (Threads per Inch) Be sure to find out the correct size and TPI for your motor.
Auto parts house for a 3/8 16 TPI Heli-coil kit that comes with coils, coil driver tool and the tap. (Expect to spend $20-25) The package will tell you what size drill bit you need for the job, mine was a 25/64th.
Next step was to drill out the drain hole in the lower unit. None of us wants a bunch of metal shavings inside our lower unit with all the gears and bearings. I used a shop vac held next to the hole as I drilled. Recruit someone to help or strap the hose on the unit so you can use both hands on the drill.
Ready now to tap the hole out with new threads for the heli-coil. Smear the grooves of the tap with bearing grease to catch the chips as the tap cuts. I did mine twice, cut threads in half way, backed out the tap, got rid of the chips and then reapplied clean grease to cut the remainder of the threads.
Now take your drain plug and screw it into the heli-coil without the washer gasket on the plug. Count how many coils you have extra on the coil. Remove the plug and cut those coils off with some sharp side cutters. (Don’t cut off the drive tang from the other end). Mine needed 3 coils cut from the heli-coil so it would fit. When you drive the coil into it’s new threads, you want none of the coil to stick out from the hole or your plug washer gasket won’t seal.
Coat the coil with thread locker, I used the blue just in case it needs to come back out. The coil should drive in easily and start to get a little tight towards the end. I left the heli-coil drive tang on mine rather than take the chance of breaking it off and having it fall inside the lower unit.
To be sure to have all the shavings and chips out, I rinsed the lower unit out with the milky mineral spirits using my lower unit gear oil pump. I put the hose in the top vent hole and pumped the spirits in, allowing it to run out the drain. This flushed out all of the older particles and more of the fresh shavings from the tap job. I then used my air and blew air in form the top until nothing came out the bottom, just to get all the spirits out.
Refill lower unit with fresh oil, put your drain plug in it’s nice new steel threads.
Hope this little tutorial helps someone in the future.
