lower unit bolts cross threaded-Johnson 200 '91

[robc]

We were trying to drop the lower unit to replace the water pump but gave up because it would not budge.<br /><br />When torquing the bolts, the two on the left side in front wouldnt tighten and cross threaded.<br /><br />Can larger bolts be tapped into the stripped threads without needing to remove the lower unit? and if so, how would we do it ?

 

[R.Johnson]

Re: lower unit bolts cross threaded-Johnson 200 '91

You went from removing the gearcase, to stripping the thread's. Did they strip on the way out, or trying to put them back in? You may be able to clean the threads with a tap. You can turn the tap with a 1/4" wrench with the gearcase on, going 1/2 turn at a time, or remove the gearcase, and use a tap wrench. If the thread's are totally damaged, you will need a Heli-Coil, or go oversize

 

[robc]

Re: lower unit bolts cross threaded-Johnson 200 '91

we were trying to put the bolts back in. when i took one bolt out, there was what looked to be metal shavings within the threads of the bolt, so i thought uh-oh...<br /><br />i heard of a heli-coil to insert into the leg and put a bolt in that is larger.<br /><br />does the gearcase need to be removed to insert the heli coil?

 

[DHPMARINE]

Re: lower unit bolts cross threaded-Johnson 200 '91

I think you have to get that lower unit off to do anything more.Larger bolts will need a larger wrench size so that won't work.<br /><br />Helicoil time.<br /><br />DHP

 

[robc]

Re: lower unit bolts cross threaded-Johnson 200 '91

would a heli coil insert be strong enough to withstand the torques exerted when the engine is pushing the boat in the water ?<br /><br />i am pretty sure i have the space to use a larger bolt and i can get a straight shot at the front bolt hole, but the lower unit has a flange type of protrusion under the bolt hole so that i can only get a box wrench on the bolt and not a socket.

 

[rodbolt]

Re: lower unit bolts cross threaded-Johnson 200 '91

no larger bolts. not enough space. remove the case and helicoil it and clean the original bolt threads and reuse them.<br /> nect time instead of thinking uh-oh think a bit farther and run a die down the bolt and a chaser tap up the threads and you will avoid problems.

 

[robc]

Re: lower unit bolts cross threaded-Johnson 200 '91

thanks for the advice guys-- - <br />it sounds like the lower unit really needs to come off<br /><br />we started this project cause of overheat at start up this year. one engine went fine--because the p;owerhead was rebuilt two seasons ago.<br />this engine though has not had a water pump replacement in years so the driveshaft is rusted to the crankshaft.

 

[robc]

Re: lower unit bolts cross threaded-Johnson 200 '91

thanks for the advice guys-- - <br />it sounds like the lower unit really needs to come off<br /><br />we started this project cause of overheat at start up this year. one engine went fine--because the p;owerhead was rebuilt two seasons ago.<br />this engine though has not had a water pump replacement in years so the driveshaft is rusted to the crankshaft.

 

[robc]

Re: lower unit bolts cross threaded-Johnson 200 '91

the bolts that stripped were a 3/8" coarse thread. the socket size was 9/16"<br />does that mean the helicoil we insert should still use the original 3/8" bolt -- <br />does the tool that drills out the bolt hole for the helicoil make the bolt hole much larger ?