Stuck propellers are a common problem for all boats. In the case of the Mercruiser Alpha I outdrive, a stuck prop is normally caused by inadequate marine grease on the prop shaft or going too long between propeller service. When approaching a stuck prop on the Alpha or other outdrives, a bit of patience can go a long way towards a positive outcome.
Preventative Measures
As they say, ‘an ounce of prevention ..’. In the case of Mercruiser propellers, they should be removed at least a few times per year (more often if the boat is kept in the water). This simple act is likely the #1 way to prevent a stuck prop. When reinstalling, a liberal application of marine grease is also a must to improve your chances of keeping everything unstuck.
Unsticking a Prop
First, let’s cover a big Don’t-
Getting aggressive with a hammer - The prop shaft (to which your prop is stuck) is connected to the lower unit gearing which can be damaged by sudden impacts. The outdrive case and often prop are made of aluminum which are much softer than your normal hammer too.
Escalating Steps
Have you biggest, strongest friend come and give the prop a good pull
Use a ‘Penetrating Oil’ such as kriol or breakfree to attempt to loosen the prop. This method will take time -a few days to a week - if it works at all.
Buy/Borrow a Prop Puller (similar to a bearing puller but with smaller arms to fit through the exhaust ring). Not all props have enough clearance to get the puller arms through the exhaust ports and behind the prop.
Torch it off. This is easily the most drastic method and you will be in the market for a new prop if you weren’t already. It is also very easy to do this wrong and smoke your lower unit seals and/or warp the lower unit casing - both a bad thing.
Personal Experience
We inherited a stuck prop when purchasing our 1st boat, a Chaparral 1935SS cuddy. The prop was in good condition so we weren’t in any hurry to get it removed, but did want the option to switch props with ease.
The strong friend method didn’t work so we reverted to the penetrating oil technique. I used an off brand aerosol oil from Walmart which cost around $4.00. Proir to spraying, I trimmed the outdrive all the way up so gravity would help a bit.
The prop didn’t seem to budge after a few days so I was getting concerned I’d be progressing to the torch stage. At that point, work interviened and I let the boat sit for a week. Prior to replacing the prop nut for an outing, I decided to give it one last hard tug. I just about ended up on my back as the prop slid easily from the shaft. Since then, we never had any additional problems until selling the boat this spring. An upcoming project is to service the props on our Regal’s twin Bravo III outdrives. Hopefully they won’t be stuck.
