Prop repair gurus... can I cut this off?

[Homerr]

I damaged my prop near the end of last season. Nothing major - just hit a branch while backing off the beach. No fin damage - but the outer 'bell" has some battle-damage. Please look at my picture. The OEM # of the prop is: 48-834852A45. Mercruiser Alpha One Gen 2., Bayliner Capri 2150 LX.

Question: Can I simply trim the damaged portion off this prop? it wouldn't be much - maybe 1/2' to 3/4"?
I am a machinist, so it would be a simple matter of putting it in a mill or lathe and shorten. I just wasn't sure if it would cause any performance issues. I dont' see how it could, but I'm no expert on props.

Normally I would fix the prop without question, but I recently I bought a new prop for a backup and noticed it's 'bell" is much shorter than my damaged prop. In fact, it's about 1/4 the length? The new prop is the same size and diameter. Only the end length is different.

If the damaged portion of the prop can simply be removed without any ill-effects, it would certainly save some machining time. I'm not sure what I could do to straighten it back out. I have a few tricks up my sleeve of course, but I am grossly limited by my lathe's capacity. Thus the reason I am considering my mill instead and just cutting it off just below the damaged parts.


Thank you!

 

[poconojoe]

I don't know about trimming the old prop, hopefully someone else will chime in on that. If I were you, I would put that new one on and use the old one as a spare.

 

[Scott Danforth]

I would take 3 minutes with a pliers, file, and rattle can of paint and you wouldnt know you nicked your prop without having to cut anything.

 

[Gibsonman2005]

I would take 3 minutes with a pliers, file, and rattle can of paint and you wouldnt know you nicked your prop without having to cut anything.

I would also bust out a file and some pliers. The main problem I could predict if you remove a portion of the prop is that it may not be evenly balanced when it spins. You don't want it to wobble.

 

[Maclin]

Just my opinion, but I would just run it like that, especially if that is the exhaust outlet end, unless the edge where the most damage in the photo at the left is ripped. It is only affecting "things" when on the trailer, those "things" being pretty much all aesthetic. In my opinion, being the damage is on the hub and really close to the spinning center the effect on balance is negligible if any if material has to be removed. I would only remove material if there is a rip in the aluminum, to ensure it would not "spread" somehow, and only around the ripped area. If it really bugs you then repainting should make it almost unnoticeable from 10 feet and out. If it is on the other end and it is not hitting the lower unit carrier then same advice.

 

[jimmbo]

Well you can try it, but there is a chance the exhaust gases could be pulled into the blades and resulting in slippage. There is a reason the hubs are extended, if the wasn't, the prop makers wouldn't be using the extra metal

 

[Maclin]

To Jimmbo's point, all of the props I have had with thru-hub exhaust have always had a flare out right at the end. Figured it was to create a slight vacuum of sorts in the water flow to help exhaust gas scavenging.

 

[jimmbo]

To Jimmbo's point, all of the props I have had with thru-hub exhaust have always had a flare out right at the end. Figured it was to create a slight vacuum of sorts in the water flow to help exhaust gas scavenging.

For years OMC, instead of a flair, used a converging ring to push water into the low pressure area behind the prop. A lot of props(RAKER) have neither and are just a straight tube

 

[Texasmark]

I would go a pair of hammers, one inside and one outside and "peen" it back in shape, and trim with a file. Then if you like, hit it with Merc Phantom Black after sanding and priming.....let it dry thoroughly. But I could also leave it alone as is or use the file and pliers method.

The bell and flare or in the case of OMC when they did their first Stainless Steel Teflon (coated) SST (1973) the bronze convergence ring, or just a long barrel (tube) is to reduce the possibility of exhaust gasses getting in the prop's clear water and causing ventilation; nothing more nothing less. How much and what you need depends on lots of things. Once you whack it off it's whacked and if you needed it and find out later, you can't very well back up.

Edit: Just a side note on what I said. I had a 1972 Johnson 125, bought in that year. The only props available at the dealer were white alum. I got tired of having to either clean up the blades after the outing, or Monday lunch time, run the prop over to the local prop shop and get it repaired. I could get in a thicket of 2" willow saplings maneuvering through them at idle and wind up with a dinged prop.

So, (if I recollect correctly) the next year (1973) OMC comes out with an after market tilt kit for it, which I managed to acquire....trim was not available for my engine but the new ones had it (again as I recall), and a new to the market Stainless Steel prop covered in Teflon. Cost was $185. It was a strain for me to get it but I worked it in the budget and kissed the trips to the prop shop goodby....which over time paid for it. That's why I know (think I remember) the year.

 

[jimmbo]

The SST prop was introduced in 1971, The power tilt system was a dealer installed option beginning in 1960. Power trim was first offered in 1973

 

[Texasmark]

The SST prop was introduced in 1971, The power tilt system was a dealer installed option beginning in 1960. Power trim was first offered in 1973

Thanks. So, plugging that into my past life, I started out with a non power tilting/PTT engine with alum. props on a 1972 year model. Got tired of tearing them up so THEN I started being more observant and found the SST was available...probably took me a year to get to that point. Same thing on the tilt but not sure about the 125 adapter being that far back since they didn't make it till that year....I think the '71 limited at 100 and I recall the '73 came in at 135 with a black hood (decal) rather than white paint like mine. What I really wanted was PTT but it wasn't an option until the '73 model (there's the '73 in the equation) but my '72 transom bracket wasn't made to accept it so I couldn't use it.....I think. This is sort of getting off topic, but it is related.

 

[jimmbo]

With a bit of latitude from the OP please

The pre 73 transom bracket clamp wasn't strong enough to handle a power trim system. If you remember, there were two clamp brackets that were bolted to the transom and then the engine was lowered vertically between them. Then two pin bolts at the top of the brackets were screwed in so the engine couldn't climb up and out. It was strong enough for an engine that didn't move around a lot, but trimming the engine underway would have probably sheared the two pin bolts, especially on engines that were clamped at a higher transom height. In 73, they deep sixed the slide in bracket and went to the fixed system, made removal of the engine slower but it was more secure.

 

[Texasmark]

With a bit of latitude from the OP please

The pre 73 transom bracket clamp wasn't strong enough to handle a power trim system. If you remember, there were two clamp brackets that were bolted to the transom and then the engine was lowered vertically between them. Then two pin bolts at the top of the brackets were screwed in so the engine couldn't climb up and out. It was strong enough for an engine that didn't move around a lot, but trimming the engine underway would have probably sheared the two pin bolts, especially on engines that were clamped at a higher transom height. In 73, they deep sixed the slide in bracket and went to the fixed system, made removal of the engine slower but it was more secure.

Back to the original post (OP) essentially: The bronze ring on the SST was easily knocked off by bassers in particular...motoring around "structure" constantly. The guys I know that knocked them off never complained about cavitation or ventilation. The barrel was straight, not curved like yours so you just never know if cutting it off would hurt you or not.

Back to the '73: When looking for adapting a 73 to my 72 I did notice quite a difference and that and price for bracket and trim kept me from jumping in.

Again sorry for the slight divergence but I think we offered enough info in this post to consider the question answered. You agree Homer?

 

[jimmbo]

I think we offered enough info in this post to consider the question answered. You agree Homer?

Sure Mr. Griffen

 

[Texasmark]

Sure Mr. Griffen

Homer started this thread. Don't know who Mr. Griffen might be.