Prop problem

[lgaytan]

Hi, so I went to the lake yesterday an hit some rocks after launching the boat and it stalled, not a big hit apparently although after that we started boating no major issues at low speed then when I started to increase speed motor went high in revs but no more speed, felt like no power was transferred to the prop. No grinding noise or anything that indicates issues in the transmission, today at home I put the engine turned off in forward and locked the fly wheel and tried to spin the prop with my hands, I'm able to do it so I believe the inner hub of the prop is damaged Question here is if this reparable it I have to get a new prop?

 

[lgaytan]

Hi, so I went to the lake yesterday an hit some rocks after launching the boat and it stalled, not a big hit apparently although after that we started boating no major issues at low speed then when I started to increase speed motor went high in revs but no more speed, felt like no power was transferred to the prop. No grinding noise or anything that indicates issues in the transmission, today at home I put the engine turned off in forward and locked the fly wheel and tried to spin the prop with my hands, I'm able to do it so I believe the inner hub of the prop is damaged Question here is if this reparable it I have to get a new prop?

View attachment VID-20250907-WA0009.mp4

 

[flashback]

Yes its repairable, a new hub will be needed.

 

[lgaytan]

After watching some videos on YouTube I find out that the purpose of that hub is actually tu spin when the prop hits something, so based in the video do you think is damaged or just as it should work? Another why I wouldn't get to speed up if the motor was revving up?
Thanks

 

[tphoyt]

Your answer is in post 3.
The prop hub did what it was designed to do and failed before damaging the more expensive parts.
They are a sacrificial part. It will hold a lower speeds and usually get you home but the faster you go the more the hub slips.
Hope that helps.

 

[lgaytan]

After inspecting my prop and seeing some videos I think that hub repair is beyond my skills and available tools, maybe a new one is the best option.

 

[lgaytan]

My prop

 

[lgaytan]

Some questions... My prop is part number 48-76228A4 13, I can't find new ones just some used in ebay, being this very old props and that the hubs can fail I don't want to buy a used one does anybody knows what would be a replacement for that one? Also I wonder if now that I'm buying a new prop I should stay with the same pitch, the boat is an old 1976 fiber glass V Hull about 15 foot with the 50hp it goes about 25-26 miles per hour, I don't have a tach to know the RPMs, anyways any advise is welcome.

 

[flashback]

A good prop shop could press a new hub in if the blades and body is OK.

 

[lgaytan]

Unfortunately I'm located in an area that don't have that kind of shops, is easier for me to get the spares shipped to me than replacing.

 

[airshot]

Without a tach, you would only be guessing to the pitch needed. If pitch is to liw, the motor will over rev and shorten its life. If there is to much pitch, the motor will lug, work hard, use excess fuel and can shorten its life. The proper pitch will allow the motor to reach max operating rpm so your engine makes the most power effieciently. If your going to keep the boat....you need a tach ! Should not be a problem finding a prop for your motor unless it is an antique.

 

[lgaytan]

Yes I'm thinking in having a Tach, however to properly select a propeller I guess I should have some different Props available, test with the Tach and then select and buy the definitive, as I don't have them I think the most secure way to do it is just buying one same size at it had before, after all this motor has lasted already 49 years, I don't know if this is the original but at least in my possession it has been 20 years, so I would think that was a right propeller. I wanted to try something witha higher pitch to get a few more mph, but maybe that is not what my focus should be.

thanks

 

[airshot]

Once you know the rpm of your motor at wot, then we can calculate how much pitch to add or subtract to get you the correct pitch for the health of your motor. However, if your motor is running well after 20 years with your current prop....don't try fixing what isn't broke !! Trying to gain a couple mph often creates other issues. When gaining more moh, you loose hole shot and performance with extra passengers. One prop will not do everything well, folks that use their boats for all types of activities, often carry 2 or 3 different props.

 

[lgaytan]

I was able to find a shop that repairs propellers, is 500 miles from my location, I guess having a boat living in a place without lakes nearby has its downsides... but I think this is the best way to go, I'll get this one repaired, and later with a Tach I will see RPMs to decide if a change is needed

 

[Chris1956]

Gee, How about buying a new prop with the same pitch and style. An aluminum version will be about the cost of the rehub, and you will not need to drive.

 

[lgaytan]

I will ship it to the repair shop, I have read that aluminum props are not as efficient as the Stainless steel so I don't want to go that route. The rehubing and shipping estimates I have right now are $125 dollars. A new (chinese) SS prop is about $180 dollars, hoping this guys know what they are doing I think this is the best option

 

[Chris1956]

OK, you might check your prop shaft for straightness. When SS props hit rocks, the prop shaft can be bent.

Aluminum props usually break and protect the prop shaft.

 

[cyclops222]

Old wives tale. Aluminum props do break drives. Real crash tests proved there is little difference..

 

[airshot]

Old wives tale. Aluminum props do break drives. Real crash tests proved there is little difference..

Not according to Michigan Wheel prop mfgrs. When identical hard strikes take place with SS and aluminum props, the chance of internal damage is almost 70% higher with SS. In light strikes the SS suffers less damage than aluminum. Then compare original costs...SS is typically 3x the cost of aluminum, and even higher for a performance prop. SS props are better suited to create customization to address certain issues like excess bow rise, or stern heavy issues among others. For general use, aluminum props are recommended by most mfgr. SS are typically for performance operations or when certain design mods are needed.