Prop shaft seizing

[Ken McDonald]

Hi I'm a new member and in need of some mechanical advise; on my 1987 3807 aft cabin with 454s. The starboard engine prop shaft does not turn freely. With the transmission in neutral the port side prop shaft turns by hand where as i need to use a pipe wrench to turn the starboard shaft. I tried disconnecting the shaft from the transmission and got the same results. One of the symptoms is a vibration in the starboard engine at any speed, both in forward and reverse. Any thoughts of what it could be or what additional diagnostics i need to do would be appreciated.
Thanks
Ken

[Viper]

Most likely the forward and aft struts on that side are not aligned properly. She probably had an impact at one time and the alignment wasn’t checked. You’ll have to wait until she comes out of the water to check that and correct it. That won’t be long now!

[KyleR]

Welcome aboard!

I agree with Viper. Also while it's out of the water make sure you check the "trueness" of your props. Our starboard prop was almost 0.5" out of true indicated by taking a measurement at the top of the prop to the rudder, rotating 180deg and measuring the top of the prop to the rudder again. It caused some pretty significant vibrations that transmitted through the whole drive train including shaking the engine!

Keep us posted on what you find!
Kyle

[Ken McDonald]

Sounds correct. Previous owner told me he hit a rock and damage the starboard side. Changed the shaft and prop but nothing was done to the struts. Aside from the suggested prop to the rudder measurement what other measurements can I take to verify the strut alignment? How big a repair is this?

Thanks again Ken

[Viper]

While blocked on land, remove the prop, disconnect the shaft from the coupler and pull the shaft back until it clears the forward strut. With the shaft set true in the aft strut, check whether it will slide through the centre of the forward strut without forcing it one way or the other. If it’s not pointing to the centre of the strut it’s most likely your aft strut is bent. Depending on the severity of the bend, you can straighten it in place but that requires a custom made tool to keep the bearing cool while you heat the strut, an old shaft to tweak the strut left or right, and a way to straighten the strut if it has a curl in it; usually with a very large pipe wrench for example. Short of that it’s removing the strut and taking it into a prop shop for assessment. They would determine if it can be straightened or if a replacement is in order. Personally, since one has to go through the trouble of removing the shaft and prop, I would send them in to get checked as well, most shops will do that free of charge and give you a report. After you have everything back together again, you have to check/do a final engine alignment after she gets launched and is in the water for a day.

[Ken McDonald]

Thank you for such precise and clear instructions. I’ll probably remove the propeller and shaft myself to assess the damage then have the marina guys fix the strut. As well I’ll definitely get the prop and shaft checked out. The boat comes out of the water in a few weeks I’ll let you know how I made out. Your help is very much appreciated.

Thank you Ken

[Ken McDonald]

Thank you for such precise and clear instructions. I’ll probably remove the propeller and shaft myself to assess the damage then have the marina guys fix the strut. As well I’ll definitely get the prop and shaft checked out. The boat comes out of the water in a few weeks I’ll let you know how I made out. Your help is very much appreciated.

Thank you Ken

[Ken McDonald]

Thank you for such precise and clear instructions. I’ll probably remove the propeller and shaft myself to assess the damage then have the marina guys fix the strut. As well I’ll definitely get the prop and shaft checked out. The boat comes out of the water in a few weeks I’ll let you know how I made out. Your help is very much appreciated.

Thank you Ken

[Ken McDonald]

Thank you for such precise and clear instructions. I’ll probably remove the propeller and shaft myself to assess the damage then have the marina guys fix the strut. As well I’ll definitely get the prop and shaft checked out. The boat comes out of the water in a few weeks I’ll let you know how I made out. Your help is very much appreciated.

Thank you Ken

[Ken McDonald]

Thank you for such precise and clear instructions. I’ll probably remove the propeller and shaft myself to assess the damage then have the marina guys fix the strut. As well I’ll definitely get the prop and shaft checked out. The boat comes out of the water in a few weeks I’ll let you know how I made out. Your help is very much appreciated.

Thank you Ken