Boats For Sale:
Coupler Bolts |
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marksa1458 
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Joined: April-15-2009 Location: Webster, MA Status: Offline Points: 30 |
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 Topic: Coupler BoltsPosted: October-26-2022 at 12:46pm |
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Replaced one of the isolater bushing mounts on a 2000 Ski Natique with the 5.8HO. As part of the process, I removed the coupler bolts to check and align the engine. When removing the coupler bolts, one of them came off hard and ultimately has bad threads. Ordered a new set from Ski Dim and they are shorter than the originals (see pic below) The new bolts are too short to engage the nylon part of the nut and won't work. reached out to SkiDim and this is the only coupler bolt they sell for a Nautique  It doesn't appear that the PO made any modifications here and all looks to be original. Any reason why there would be different bolts in this set up? Will have to source locally to replace
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Gary S
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Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Posted: October-26-2022 at 2:09pm |
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Don't over think this, their just bolts. Skidim just got it wrong. Go to the hardware store,go to Mcmaster Carr, go to General Propeller- whatever you want. Just for reference here is General Propeller,they don't don't mention stainless or even look it but note the size - http://www.generalpropeller.com/inboard-shafts-and-couplings/nuts-bolts/Coupling-Flange-Bolt-Sets/BOLTSET375
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marksa1458
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Posted: October-26-2022 at 2:45pm |
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Got It! thanks
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11112 |
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Posted: October-26-2022 at 5:02pm |
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How about a picture of your all original looking setup.
You don't have one of those hard rubber spacers between the coupling halves do you?
The 1 3/4 (edit, really 1 1/2) inch bolts you have would be too long for the original setup. The 1 1/4 inch bolts from SkiDim should be the right size if things are original |
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marksa1458
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Posted: October-26-2022 at 9:42pm |
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No plastic or rubber spacers
    Looks original - no? |
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KENO
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Posted: October-27-2022 at 7:59am |
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Boy, I'm glad I didn't ask for a closeup shot
 The first thing I notice is lock washers and nylock nuts used together. I tend to think that originally there was a fine threaded bolt, a lock washer and a regular nut. Then I looked at SkiDim's website and see coarse threads with a lock washer and nylock nut.and say Why, why, why? I figure that "you have what you have " for couplings whether the shaft side is original or not, so whatever length works for you is good. I don't know if 1 1/4, a lock washer and regular nut will work for you I also figure the shaft and/or coupling has been out of the boat before since there's a one piece safety collar on it, so maybe the shaft and coupler are original or maybe not. Being new to you, this must not be the same boat that you're replacing your 19 month old remanufactured engine in?
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marksa1458
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Posted: October-27-2022 at 9:02am |
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I replied via my tablet and the pics didn't look so big on that screen.....
 When I pulled the bolts there was no lock washer, just the nylocks. Since the SkiDim replacement set had the lock washers, I used them. Seemed redundant to me - but what do I know? With the 1 1/4 and no lock washer the replacement bolt is to short. For the second question - this is a different boat. My other boat is a 1990 Mastercraft Prostar with a 351W. Looking to pull that engine soon. Thanks
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marksa1458
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Posted: October-27-2022 at 9:53am |
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Here is Cylinder 5 on that 351W  |
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KENO
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Posted: October-27-2022 at 1:32pm |
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Like you're doing, I'd just use whatever works for bolts and your choice of nuts, lock washers etc.
One cylinder looking like that, I'd probably be thinking lean because of an air leak like maybe on the intake manifold gasket
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marksa1458
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Posted: October-27-2022 at 3:18pm |
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I believe in leaned out as well. The intake manifold was re-torqued twice after break in, but when I pulled the head the intake manifolds bolts were not as tight as would be expected.
 Compression on that cylinder was 85 and the rest were between 130 and 140 before I pulled the head to look. |
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MechGaT
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Joined: March-09-2015 Location: Chattanooga Status: Offline Points: 271 |
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Posted: October-29-2022 at 7:12am |
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I’m curious, what grade of bolt are those from SkiDim? Can you give a picture of the top of the head if you aren’t sure? The ones on my coupling were grade 1 and I was wondering if that was original. I thought perhaps they want them to be lower tensile bolts so they break before other stuff and they are in shear when operating so they have plenty of strength with 4.
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'92 Sport Nautique
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marksa1458
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Posted: October-29-2022 at 7:35am |
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They are labeled
S30400 THE I am given to understand that the 304 designation is stainless and the THE is the manufacturer. The bolt I purchased locally has the same S30400 but ABP stamped on it. Tried to find what grade and I don’t believe that these bolts fall under a grading standard. To your point, I think they build in a weak spot to protect the transmission. Someone with more knowledge can probably confirm/negate that. |
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MechGaT
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Posted: October-29-2022 at 7:48am |
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Okay, thanks. With no markings like on higher grades, that tells me what I was wondering.
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'92 Sport Nautique
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KENO
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Posted: October-29-2022 at 10:17am |
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The grade markings on carbon steel bolts don't have anything in common with markings or lack of markings on stainless steel bolts,
I'm not sure how you're coming up with the originals being a grade 1, but the typical SS bolt is somewhere in the same tensile strength neighborhood as a grade 5 or 3 depending on who you listen to. Not knowing what the head of your original stuff looks like, there may be a couple of little hash marks that would tell you it's 304 SS. The THE on Andy's bolts from SkiDim is the manufacturers name like he mentioned. it stands for Tong Hwei Enterprise Co.. Some people might want to trash em' because of where they're made One thing to keep in mind is that I don't think anybody has ever come on CCF and said something like." I hit something today and sheared all of my coupling bolts right off" They're not exactly a weak link of any kind in the driveline. |
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