View Full Version : Bent strut or major misalignment?

11-23-2007, 12:51 AM
I replaced the strut bushing this evening and found either the engine is really out of alignment or the strut is bent. How do I determine which one is the case?

The old bushings were slightly worn more on one side and squeaked when I put it into drive.

Posted below are pictures of the shaft going into the boat and the misaligned coupling.

When I push the shaft into the middle of the hole the alignment seems pretty good.

What do you guys think, do I realign the engine or look at replacing the strut? I hate to replace the strut since I just went through the work of putting new bushings in the old one. If the strut is bent can you bend it back?


11-23-2007, 01:00 AM

11-23-2007, 01:13 AM

11-23-2007, 11:14 AM

11-23-2007, 01:43 PM
Using the info at hand, I'd guess bent strut. That seems way off in my mind, although I don't know too much about the v-drive setups. It definitely wouldn't leave the MC factory like that. Your boat is pretty new (IMO), did you buy it new or used? Have you smacked anything with the prop, or know it that has happened in the past?

I haven't read about many people replacing stut bushings that soon, I would guess most boats on here have never had it replaced.

Check the motor mounts to see if it looks like they have been moved A LOT. My guess is something was hit & nothing done about it, thus leaving the motor in the original position, and the strut bent.

Did you pull the shaft & make sure it is straight? Bent shaft would both cause alignment issues as well as premature strut bushing wear.

Struts can be repaired, but you should probably take to a machine shop. I bent one pretty good once, but got a new one since it was an insurance claim. The old one got straighted by a local shop, but I've never tried it out.

My order for solving this (assuming the motor mounts are not suspect for extreme movement) would be to check shaft for straightness, remove strut & have a machine shop (used to working on these) check for straightness, and rebend / replace if necessary. Good luck, looks like you have some time if you're in MN...

11-23-2007, 01:43 PM
dbl post...

11-23-2007, 06:57 PM
Thanks Ben.

I'm guessing your right that the strut is slightly bent. You can't tell by looking at it, but the shaft isn't centered in the bushing. When I took the shaft out it didn't look bent, lets hope that isn't the case.

I agree that it is unusual that the bushing is already bad, but the boat has 400 hours on it. I bought it used 3 years ago with 80 hours on it and have never had any problems with it.

I'm guessing I may have bent the strut, it is extremely rocky in Northern MN and have bumped bottom a couple of times when pulling up to different docks.

What type of caulk do you recommend to seal the strut bolts?

11-23-2007, 08:38 PM
My guess is bent strut as well. That alignment is WAY off. Check your motor mount bolts, are they all tight? Can you see any marks that would indicate that the mounts "slid" or anything? Did you boat ever need the shaft replaced after hitting rocks? If the shaft ever did get bent and replaced, good chance you need a new strut.

11-23-2007, 09:36 PM
Motor mount bolts are tight and there are no marks which would indicate that the motor slid. The shaft is original and looks in good shape.

I believe the strut has to be bent because when I force it to line up the shaft is centered in the hole that goes through the boat. There aren't any visual dings on the strut, but it has to be bent. I'm going to pull the strut out and see if i can find a machine shop can fix it or I'll get a new one.

Thanks for your help guys. Anyone know what type of sealant is used to reseal it?

11-23-2007, 09:41 PM
I would think you could put a dial gauge on it and spin it to read the runout.....

if you know anybody that's got one

$7.99 at harborfreight without base

11-23-2007, 10:13 PM
Look at this thread...just in case


11-24-2007, 12:37 PM
So I have shaft out and all the bolts which hold the strut on, but that dang thing won't move. The silicone/glue they used to hold it on the bottom of the boat is some strong stuff.

I'm sure it doesn't help that it's probably 40/50 degrees in the gargage, but does anyone know anyway to loosen the glue?

I am using denatured alcohol to try to and loose it up, but it's hard to get it to soak in when your working above your head.

11-24-2007, 01:29 PM
Use a rubber mallet beleive it or not, they don't come off easily

11-24-2007, 02:30 PM
Use 3-M marine sealant when you put it back in.

11-24-2007, 03:03 PM
I don't claim to be an expert, but I'm not sure I'd use "3-M marine sealant" when you put it back on - especially if you're talking about the common 3-M 5200 sealant: http://www3.3m.com/catalog/us/en001/auto_marine_aero/marine/node_GSWWSBSW85be/root_GST1T4S9TCgv/vroot_GS4JK4Y166ge/gvel_QH8HT14PGTgl/theme_us_marine_3_0/command_AbcPageHandler/output_html

It pretty much won't let go; if you're having a great deal of trouble removing the strut when you have something as wimpy as Silicone is holding it in place, imagine your next repair after you've glued the strut in place with something that's as likely to rip bits of gelcoat off the boat as it is to release from the surface.

If you have to pound on it with a mallet to get the current sealant to release, it sounds like the current sealant is a fine solution for your needs.


11-24-2007, 04:49 PM
JR, I have not dealt with bent shaft struts myself (I have done shaft alignment on a v-drive like yours), but after reading your post and the replies here I have one small suggestion to make: When you get the strut loose from the hull you might try reattaching it loosely with the bolts, then reinstall the shaft and see if there is enough slop in the strut mounting to allow centering of the shaft in the hull shaft log mount. I was wondering if your shaft strut alignment problem could posibly have been there from the beginning and the wear in the strut bearing is evidence of the boat running since new with this built-in misalignment. And if there is not enough play in the shaft mounting to allow proper alignment you would know for sure that the strut is in fact bent.

11-25-2007, 08:19 PM
I had to bend a new strut to get it to align with the hull hole. I did use an old shaft to bend it though.

12-07-2007, 02:49 PM
this problem is pretty common and you should probably see a dealer they can tell you if its bent or not at a pretty quick glance and as far as having any underwater gear trued dont waste your money just buy a new one the labor involved is to extensive(the juice isn't worth the squeeze)

12-07-2007, 04:48 PM
There is no real mount of slop in the strut alignment. When the boat is built the hole is marked to thr strut and then drilled. A new strut can be slightly different from in side to side alignment. Its move the strut or move the hole. My new strut bent quite nicely to the side with a firm pull on my old drive shaft. Then the shaft hit the hole almost perfectly.

12-17-2007, 05:21 PM
I had this same issue. The following is a quote from me, from another thread. Reading it will tell you every thing you need to know...

I have more time today so I thoguht I'd copy and past the pertainate infor here. As you will see, I think a proper drive train alignment starts w/the strut mounting. Read on to see why...


The Prop shaft postion (centering) in the log IS important. The shaft not being centered won't cause a vibration, but it absolutely WILL cause abnormal and excessive wear of the packing, as the shaft will essentially be "pushing against one side" of the ID of the packing.

I had this very issue when I first bought my '92 (same hull as yours). When I first bought the boat the prop shaft was pushing to the side of the packing so hard, it was litereally "sawing" through the bronze packing housing -the "adjusting nut"! I determined that my strut was bent slightly, and my prop shaft had excessive runout -by putting it in a lathe and using a dial indicator. I ended up buying:
*new prop shaft from SKIDIM,
*having the prop balanced
*new strut from Mastercraft.
*new cutlass bushings.

I installed the strut first, then slid the shaft through. The strut was such that the brand new propshaft actually HIT the ID of the log! Assuming the new strut was defective, I returned the strut and got another new strut from MC. Took it home and installed it...same thing.

There was no where near enough latitudinal "slop" in the bolts/holes to allow me to rotate the strut enough to get the shaft away from hitting the log...never mind getting it centered in the hole. I removed the strut, and used a die grinder to laterally oblong the strut mounting holes in the hull. I then installed the strut loosely and sent the prop shaft through. With a partner holding the prop shaft centered perfectly in the log, I tightened the strut bolts, and verified that the shaft was still perfectly centered. THEN, I proceeded to align the engine/trans to the newly, geometrically correct drive line. This results in less friction and wear of the goofy packing and you now KNOW that everything is stright, in-line, and properly centered. FYI, I also ditched that dumb, low-tech packing for a PSS seal. The drive system is so perfect now, you can turn the prop easily w/your pinky...something that was not even remotely possible when I first got it (took two hands!).

Soooo, IMO, I would START by doing what ever you have to do to get the propshaft centered in the log, THEN move your motor to accomidate that geometry. HTH.


With regard to centering the propshaft in the log....

I just we just "eyeballed it". The centering of the shaft in the log is not SO critical that it needs to be measured, IMO, ie.. thousands of an inch, but you do want to get it as centered as possible and you can eyball that pretty good, using the log-hole as a guide. PLUS, there is enough slop in the cutlass bushings (even new) that up by the prop log, the prop shaft can be moved slightly up, down, left and right from where it wants to lie naturally in the cutlass bushings. My goal in mounting the strut, was to get the shaft as close to centered in the log as absolutly possible (+or- slop in the bushings), so that what ever type seal I chose to use, the seal would not have any side loading on it at all.

Then, like I said above, I spent a good hour or so, moving the engine/trans around to accomodate that new propshaft geometry, getting the engine/trans aligned to the propshaft...perfectly.


With regard to doing a quick check of drive line alignment...

An edit to an earlier post of mine. I was in my garage earlier this evening, and since this was fresh on my mind due to this thread, I went over and gave my prop a spin. I CAN in fact turn it w/my pinky, even dry. It's been in the garage since late September, and being in UT, that's about as DRY as you can get!

12-17-2007, 10:01 PM
Thomas, am I correct in assuming your strut alignment problem was built-in at the factory and was not due to damage? You mentioned that you had tried multiple replacment struts and they all resulted in the same bad shaft location. If so, that indicates some pretty shoddy workmanship by MC. You would think MC can do better work than that.

12-18-2007, 10:45 AM
Thomas, am I correct in assuming your strut alignment problem was built-in at the factory and was not due to damage?
That is correct. The holes for the strut were such that the strut did not point directly at the log-hole center. This could only have come this way from the factory. My boat is mint, and I mean MINT (search for pics I've posted) and there are no signs of any damage to the hull etc. I had to modify the strut mounting bolt holes to get enough lateral movement out of the strut, to get it pointed in the correct direction. If another boat's issue was less severe than mine, one may be able to get the "travel" needed with just the slop in the bolt holes.

You mentioned that you had tried multiple replacment struts and they all resulted in the same bad shaft location. If so, that indicates some pretty shoddy workmanship by MC. You would think MC can do better work than that.
That is also correct, and yes, you would think so. I certainly did when I first bought my MC, what with MC's reputation. But I've since learned that MC's marketing and reality aren't on the same plane. Not even close, really. Even though my boat was an extremely well maintained 180 hour boat when I bought it, it still needed many issues resolved that were a result of poor design/assembly at Mastercraft. Once I got all the issues properly addressed, it's been an exceptionally reliable boat, and a pleasure to own. The initial "discovery" of the reality of an MC vs. what I thought an MC was though, was a little tough...especially after (or during actually) some hefty monthly payments. :(

For the record, it should be noted that I've found this same issue on other brands of inboards, so I'm not "ragging on" or singling out MC here, just stating the facts. Ultimately, on any inboard, a good and proper alignment STARTS with the strut, and ends at the motor mounts. This is not covered in the MC owners manual, and took some time for me to "discover" on my own.

12-19-2007, 09:44 AM
I too have gone thru the MC "reality vs. expectation" learning experience like you. It appears to me that MC does use top quality materials in their boats, but the workmanship quality is not up to what I expected given MC's marketplace reputation.
I have also found some things on my boat that were not "done right"

12-19-2007, 04:14 PM
Good post, and one of the more honest assesments of ones boat, that you'll find on this forum. Many people, once they've spent the money refuse to acknowledge the issues that are clearly present w/these boats. Wierd. The ones that do however (like you), end up addressing these issues, and ultimately end up w/a better boat.

Good luck w/your alignment, and let me know if you have any more questions.