Mercury 650 lightning 65 hp cover nut troubles

[Kalvyn]

I have a 1969 Mercuy 650 lighning 65 hp motor. Bought the boat last year and remodled the inside. Motor sat for ?????? god only knows how long. Fixed a few things on the motor such as wires, plugs, throttle linkage, ect. Motor runs great. Had it in a mess tub and all kinds of gunk came out of the lower unit. Bought a manual and took the unit apart. removed bearing carrier. Everything looks good. Changed seals and went to put lower unit back together. Needed a special tool so i made one instead of paying 115 dollars. Tool works great. Went to torque the cover nut assembly to finish the project and the cover nut got to roughly 75 ft lbs of torque before jumping threads. The manual calls out for 210 ft lbs for my style of unit. the housing and nut are both made out of aluminum. is that the correct torque and if so can i get by with less? Threads look fine on housing and nut. Gonna try a new nut

 

[Maxz695]

Re: Mercury 650 lightning 65 hp cover nut troubles

because the tourque is so high I guess they made aluminum nutts to give rather than strip the threads in the unit i would figure. Possibly you are supposed to get new nuts every time you take it off like an engine headbolt. just a thought though maybe you better replace bolth nutts if you ganno replace one sounds like the other one may have stess and may cause problems down the line, after re reading your post is the stud spinning or the nut when you touqued it to 75 LBS that would not be good You say the nut threads on the nutt look good and the stud threas look good that leads me to believe it is stripped in the unit side of the stud get it repaired

 

[Wingedwheel]

Re: Mercury 650 lightning 65 hp cover nut troubles

That sounds high for a retaining nut, but if thats what the manual says then it must be so. The reason for the torque specs is because if you don't get it tight enough, water will enter the LU through the carrier seals. If you're jumping threads then something is not right. Are you sure you didn't get the nut cross-threaded? You are talking about the retaining ring I'm assuming.

 

[ONERCBOATER]

Re: Mercury 650 lightning 65 hp cover nut troubles

I am thinking it might be good to have a buddy (or a IBOATS forum member) double check for you on the torque spec.....
umm was it 210 ft lbs.... or 210 inch lbs....HUGE difference common mistake. and would change things by a factor of 12.... 210/12 would be like 17 point something ft lbs which is still a good bit for a smallish bolt and nut. what is the bolt nut diameter or wrench size?

Sean

 

[Kalvyn]

Re: Mercury 650 lightning 65 hp cover nut troubles

Thanks for all the comments. Maybe i wasn't clear enough on the area of work because of all the comments about the studs. I replaced the seals on the bearing carrier inside the gear housing. The gear housing has a female thread on the id(inside diameter) of it.The nut I'm trying to torque has and od (outside diameter) of roughly 4 in with male threads on the od. It seats the bearing carrier inside of the gear housing.
Since there is so many responses i will designate the responses.

Maxz695: The retaining nut is slipping when trying to apply torque. The threads in the unit are still heavy so i don't think that is the issue. I am going to replace the cover nut. Just need a little time.I read a comment on another forum that if you get a new nut you can cut slots in the threads to act like a tap and clean up the threads in the housing.

Wingedwheel: I thought it sounded high for a retaining nut also. Especially since it is aluminum. Since the manual stated it I thought it to be true. 100% positive that there was no cross threading. The threads didn't even shear so I have a theory that the previous owner did similar work and got a cover nut that was undersized???????? No telling though. And yes i am talking about the retaining ring (aka cover nut)

Onercboater: I have had three people read the same thing i did. The manual states to torque to 210 ft lbs or 285NM. The nut as i mentioned above is roughly 4in od with male threads. I wish it was as simple as that.Lol Do you know of anybody that could double check the torque for me?

P.S. I have a Seloc manual for Outboad Motors 1969-85 3 and 4 cyl, 40-115 hp. I also build airplane parts for a living so i know a little bit about general mechanics. Thanks for all the help and look forward to any responses.

Kalvyn

 

[Maxz695]

Re: Mercury 650 lightning 65 hp cover nut troubles

did you check the nut ID and the and the shaft OD with a micrometer? You may be right bout someone using the wromg nut on there that would explain all the junk being in the gearcase. Also do you remember if it felt like you where losening 200 FT LBS when you removed it?

 

[Wingedwheel]

Re: Mercury 650 lightning 65 hp cover nut troubles

Kalvyn. I know when I did mine I was told to set it to 90 ft/lbs. That was pretty snug. I do know that if you don't get it tight enough you'll get some water intrusion. Let me drag my manual out and I'll take a look...OK I looked and you're right. It states 210 ft/lbs. I guess I better tighten mine up. Dang I know I put around 100 lbs of torque on it and haven't had a problem, but I better do what the manual says..I wonder where I got the 90 lb #?

 

[Kalvyn]

Re: Mercury 650 lightning 65 hp cover nut troubles

Just got my lower unit back together and it works great. now i need a new control box cause it is worn out. replaced the cover nut with new one but only torqued it to 80 ft lbs cause i was a little scared but it doesn't leak so that is all that i need. thanks for all the help from everybody cause these motors can be extremely tricky if you know what i mean. Let me know if you know anybody with a spare control box in working order or even spare parts for cheap cause i'm desperate to take this thing to the lake. I'VE GOT THE FEVER... AND THE ONLY CURE IS BOATING.

 

[Wingedwheel]

Re: Mercury 650 lightning 65 hp cover nut troubles

Kalvyn,
If you don't torque it some more, you need to check your LU lube everytime out.