Mercruiser 3.7 Starter

[ImperialV184]

Hello,i am rebuilding a mercruiser 165 3.7 liter, and i am trying to bolt on the starter motor. Got a new one since the old one was rusted out. the manual calls for 60 foot pounds of torque to secure the starter......... but when i did this i broke off the bolt. the set up is confusing. The block has .5 in threads but the bolts that i removed were 3/8 x 4.5 long not using the threaded block at all. I got new class 5 bolts and went to attach new starter and the bolt broke at about 50 foot pounds, i had to use a wrench to hold the nut while i used the torque wrench on the bolt (not ideal but i could not verify torque on the nut do to clearance or lack of the right tool) When i try to buy part the schematic seams to show a fully threaded bolt going through the block with a nut on the end but the description says it is 3/8 x 4.5 which is what i removed. so confused and bummed because i am so far into this rebuild. I have read all the horror stories on this engine and have addressed all the pitfalls heat exchanger, stator replacement, cam shaft leak....etc hope i can figure this out and get this thing working, thanks for the help.

 

[Scott Danforth]

starter bolts are special grade 8.

get the correct bolt for the application

 

[ImperialV184]

OK, I will take a look at that, the bolts I removed looked like grade 5, but they could have been put in by the previous owner. do you know why the block is threaded but the bolts are undersized and don't use the threads

 

[ImperialV184]

So mercruiserparts.com and various other sites show this part as NLA, can I use grade 8 bolts form a local hardware store?

 

[thumpar]

Just make sure you get stainless.

 

[stonyloam]

I believe the early versions of the 470 used a starter bolt in that threaded hole. Here http://www.mercruiserparts.com/bam/subassembly/30926/1592/10 #2. Do an Internet search for that part number, should be able to find one. My "87" uses a bolt and nut, can't remember what size. Good luck.

 

[ImperialV184]

Thank you, that makes sense now. I bet I know why they changed it. The bolts length is limited do to clearance and I bet still in aluminum made removal a pain in the rear. I picked up some grade 8s at Fastenal yesterday. going to use them, I also did some research on torques. and 45 foot pound is what is recommended for that bolt. even at grade 9 it only gets to 50-55, I am going to torque to around 45 and keep an eye on it vs going to 60. I don't want to crack the fly wheel housing either. One note on stainless. Stainless steels is good for corrosion but not his application, Stainless is roughly the strength of a grade 2 and cant be used in this application since it can only be torqued to around 20 foot pounds. At least that is what my research showed. Would be nice since this is a high corrosion environment.

 

[stonyloam]

Yeah I bet they had some problems with a steel bolt in an aluminum block. Yeah that nut/bolt is a pain LOL! You will like that 470 when you get her running, welcome to the club

 

[bruceb58]

Just make sure you get stainless.

I wouldn't use stainless. Not strong enough and you can't easily get anything close to a grade 8 in stainless and also way to much yield.