Mercruiser 2005 Alpha one 3.0 prop and lower unit question

[powerzz]

Good day everyone,
This is my first boat that has been recently boughtt. offcourse, things have to go wrong and they did.
I hit a submerged rock and ruined the props. The previous owner modified the prop and installed 14.8 X R17. I looked high and low for the stock prop seize and could not find it.
Can anyone advise me what would be the stock or standard seize for Mercruiser alpha one 140 4 cyclinder?
Also,
I knocked the lower unit and broke a piece of the fin, not sure of the technical( please see pictures). what do i do? replace housing or weld it?
Your inputs are beyond appreciated. thanks all for your help
Mike

 

[floridaboater1]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

Not sure on your prop question. But on your lower unit the piece you broke is the skeg. If you go on ebay they have a skeg protector that would bolt on and fix/protect the skeg for about 90 dollars

 

[Pikey23]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

Check some local boat or welding shops in your area. I found a guy that welded a new skeg on my lower unit for $50. About the skeg protectors, I did a bunch of reading about them when I broke my skeg, people say that they are not good for a few reasons. First, some of them require you to drill two holes at the top of your broken skeg very close to the "bullet" of your outdrive. WHEN you his something again these holes can cause a weak spot along a the top of the remaining skeg and cause it to break off at the screw holes leaving nothing left to attempt another repair. Second, alot of the skeg protectors are stainless steel, when you hit something the stainless is alot harder than aluminum and does not give. The protector could actually end up cracking the bullet in a impact. I never experienced any of the above. They were just warning that people gave when I was researching them.

 

[powerzz]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

Thanks for the input. I decided to take it to the dealer and the will fix it for 250 dollars including painting. I am not sure how to avoid an accident like that in the future except to cross my fingers and hope for the best. Thanks again for the wonderful insights

 

[jimbo_jwc]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

My 87 came with this 48-78118-a40-17p prop its a 3.0 L Mercruiser Alpha One outdrive

 

[fishrdan]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

There isn't a "stock prop size" for a 3.0 Mercruiser as it depends on hull design, loaded weight, usage. I imagine the boat was performing great with the old 17P prop, but what was it's WOT RPM, were you shooting past 4800RPM if you hold the throttle down? If you are doing watersports the 17P prop might be a good compromise. Though, you will have to watch the WOT RPM as the engine could over rev, and the 17P prop will limit your top end speed.

Mercury has a prop selector that will help pick a replacement prop, I'd run through it and see what it comes up with. It will probably recommend a 19 or 21P prop, I'd guess.

Once you find the prop pitch, pick up a Solas Amita here at the iboats store, should be right around $100.

 

[jimbo_jwc]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

Mine is more than capable to going over WOT but when fully loaded I think things will even out to full load RPMs and yes hulls make big difference on planing speeds and top speed. Loaded back of boat big time for fishing over night needed more trim but still runs good but doesen't handle big boat waves at full throtle . Original prop for brand of boat and size ,weight,hull,and goes fast as I need .Just took 30yrs to find one for my needs . Should I be concerened about over reving for It only happens by chance and not for very long ? Motor rpms as 4200-4600 on sticker. Are there many instances of these engines flying apart when you over rev for very long?

 

[bnicov]

Re: Mercruiser 2005 Alpha one 3.0 prop and lower unit question

To avoid hitting rocks, you need a navigation chart available from local marinas. The rocks and shoals are marked. When boating in unfamiliar water, go slow. You are lucky you only wrecked the prop and took a chunk off your skeg. I boat up in Georgian Bay and the front of my 19ft'r could be on a rock and the prop has 100ft of water under it. Be careful.