Very loud rattling/knocking noise under load

Rick Stephens

Admiral
Joined
Aug 13, 2013
Messages
6,118
Does it look like the chine was glassed on over the completed hull? THat's what it looks like in the pic. From what I have seen, chines are usually built right into the mold for the hull, so it seems strange. If it was molded into the hull bottom you have a serious problem and probably the stringers are mud.
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,759
I should add that I live at 7+k elevation. So the compression numbers are lower then what they would be at sea level.

Unless you run it hot or wore it out, I'd check compression tool. You may have shraider valve sticking or not working at all. I almost pulled a 350 because of poor numbers. By chance I discovered loose valve. I don't know how it got loose. I tighten and retested all 8 cylinders to 150 +-5 lbs. I don't know about elevation factors???
 

JASinIL2006

Vice Admiral
Joined
Feb 10, 2012
Messages
5,524
Does it look like the chine was glassed on over the completed hull? THat's what it looks like in the pic. From what I have seen, chines are usually built right into the mold for the hull, so it seems strange. If it was molded into the hull bottom you have a serious problem and probably the stringers are mud.

From other pics the OP posted in the Resto forum, her has serious cracking in other places, not just along that chine. I'd be amazed if he doesn't have substantial rot in the boat's bones.
 

cruiser83

Seaman
Joined
Feb 2, 2020
Messages
73
Just thought I update on the noise. Pulled the motor which turned out to be a zz4 or L31 motor. They used the wrong coupler, it had the big triangle coupler and cut the relief squares out of the flywheel cover so that allowed the coupler arms to hit the y pipe. That's the loud klacking noise
 

garbageguy

Lieutenant Commander
Joined
May 8, 2012
Messages
1,531
considering there's evidence of hull problems, is it possible that a flexing transom could be causing the movement and resulting noises? just spit-balling
 

cruiser83

Seaman
Joined
Feb 2, 2020
Messages
73
True, but the transoms was recently done I think. It's very solid. And the wood doesn't look bad.
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,759
Just thought I update on the noise. Pulled the motor which turned out to be a zz4 or L31 motor. They used the wrong coupler, it had the big triangle coupler and cut the relief squares out of the flywheel cover so that allowed the coupler arms to hit the y pipe. That's the loud klacking noise

You have 14" flywheel? Most 350s do. Many triangle shaped couplers are for Alpha but they work on Bravos, at least mine do. Cut reliefs on bellhousing may indicate they didn't have correct bellhousing or something came loose and ate insides? Hit Y-Pipe????? That doesn't make sense, but few things do anymore. LOL and good luck!
 

Scott06

Vice Admiral
Joined
Apr 20, 2014
Messages
5,542
Sounds like they used a 14” flywheel with a older generation flywheel cover and clearanced it to fit. You can buy a 12&3/4” flywheel and correct coupler with I think should work with your older model flywheel cover. This flywheel cover also has narrower rear engine mounts to work with your transom housing.
Bondo may know more about the particulars
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,759
Sounds like they used a 14” flywheel with a older generation flywheel cover and clearanced it to fit. You can buy a 12&3/4” flywheel and correct coupler with I think should work with your older model flywheel cover. This flywheel cover also has narrower rear engine mounts to work with your transom housing.
Bondo may know more about the particulars

I think you may something! I have some smaller 305 flywheels in my shop, but I cannot remember bellhousings being smaller for 305 vs 350s? But, I am getting old. Former owners may have swapped straight drive parts for I/O parts. Now, current owner has a monkey-f! I've been burned too! This scenario is why no one touches my boat but me.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,297
most likely a 168 tooth flywheel in a 153 tooth flywheel cover

buy a new flywheel if you dont have the correct one. they are under $80. about $125 for an SFI approved one.
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,759
most likely a 168 tooth flywheel in a 153 tooth flywheel cover

buy a new flywheel if you dont have the correct one. they are under $80. about $125 for an SFI approved one.

I am trying to wrap my head around stuff slicing into y-pipes? I've owned Alphas beginning 1986 year and now Bravos. If my old memory serves me correctly Alpha and Bravo Chevy v8 bellhousings (flywheel cover) motor mounts fit Alpha or Bravo inner transom plate motor mounts. Maybe I was just lucky? I learn something new every day!!!
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,297
the flywheel for the balance shaft V6 and V8 should be the same your choice is either the 153 tooth or the 168 tooth.

the starters are either for 153 tooth flywheel (straight across) or 168 tooth flywheel (staggered). then there are the direct drive and the PMGR.... there is no "v8 starter" they are the same starter no mater if its a 3.0 or an 8.2 (other than style and spread)..... GM is easy that way.
 
Top