Damaged prop - ok to switch from four blade to three blade?

[blinddog]

I damaged my prop today, I have a spare from another boat that I used to own, but it's a three blade instead of the four blade that is on the boat now. My boat is a Centurion Carbon Pro with the 5.7 PCM engine. I have to find a prop puller before I can take the old one off, all I know is it's 13" diameter (measured), four blade, left rotating. The spare I have is an Acme 13" x 12, three blade, left turning. Any issues with swapping that out that anyone knows of? I'm guessing it would take a week or more to get the original fixed, so the swap would be temporary. Also, just ahead of the prop is what appears to be a 1" spacer that is broken, it goes about 2/3 of the way around the shaft, the other 1/3 is broken off. I have no idea if that happened today or if it was already like that, nor do I know what it is for and if it's critical. I'm trying to get back on the water without having to wait until next week when the marine shops are open. Any help is appreciated.

[skiinxs]

There are two approved props for the Carbon pro, the approved four blade is an OJ 13x 14 1/2. (OJ part number 534) That is likely the prop you have. The approved three blade is an OJ 14 X 13 (OJ part number 365). You don't need to worry about approved props unless you are pulling tournaments, I just listed them for reference. Assuming your acme 13x12 three blade is for a 1" shaft and fits, you will be way under propped with that prop and your 1.26:1 gear reduction transmission. (It is likely for a 1:1 transmission boat) You might be able to get by for a few days but you are going to be turning a lot of rpm's, kinda like going down the highway in your car in second gear. Is your 1" "spacer" in front of the strut or behind? It might be an anti-corrosion anode, or it could be a safety collar. Post a photo and I will tell you what it is.

[blinddog]

Thanks @skiinxs for the info. The spacer is between the prop and the strut and seems like it's made of plastic, but I'm not 100% sure about that. One of the guys I was with seemed to think it was a bushing and was suppose to be inside the strut (?). I will be up at the lake tomorrow, I will take a photo when I get by there. Thanks.

[skiinxs]

Oh, definitely take a photo and post. If it is your strut bushing, that is a problem you are going to want to fix before you run it again.

[oldjeep]

If it is the strut bushing then you also need to check for a bent shaft and shaft alignment in addition to fixing the bushing. Was is a hard hit on the prop?

 

 

[DW]

@blinddog : You should be able to find the prop dimensions ('dia' x 'pitch') stamped on the hub of the original prop needing repair. That should indicate if your replacement will be suitable (per the gearbox ratio comment). Going to the correct pitch 3 blade prop is not an issue and may be a performance improvement. The CNC Acme props have significantly more blade area than older sand cast props so the actual difference in blade area is less.

 

Generally speaking, a three blade prop allows the boat to hit a higher top speed and a four blade prop has a better holeshot and holds better low speed (10-20 mph) consistency. As noted, several boat manufacturers will list both a 3 and 4 blade prop option, it boils down to your specific needs and wants.

 

More importantly for you, correct the shaft bushing issue and I suggest you check your shaft for straightness, there is a reason the bushing came out or was knocked out.

[blinddog]

I hit a log, I was pulling out at the end of a 36 mph pass and had pulled the throttle back to idle/gear just before before hitting it. I pulled one more pass and there was a noticeable vibration, so I pulled the boat out of the water. That "spacer" I described is definitely the strut bushing, I was able to slide it back into the strut. I suspect the damage to the bushing was a result of the vibration from the bent prop. I am with the boat now, the prop and shaft turns freely from what I can tell, but I can't get the prop off, even with a puller cranked down as tight as I can get it.

[oldjeep]

You don't pull the prop with the puller. Crank it down and then smack the side of the puller with a hammer. Also make sure that you have not already bent the puller - may need to back it off a turn or so if it has flexed. Last guy I helped with one had torqued it so hard that it bent and was pulling crooked.

[dvskier]

Try putting some heat from a heat gun or

[UWSkier]

Did you leave the shaft nut on (but loosened) so the prop and puller don't go flying when they release?

 

Once you've got the puller good and tight, you can tap on the puller bolt with a hammer to induce a bit of vibration to get it to pop loose. Don't go whacking it with full power. Start with the kind of tapping you'd do to drive in a medium sized nail for hanging a photo on the wall. You can hit it fairly hard, but remember, that's going up the driveline so don't sledge it.

 

If that doesn't work, get out the torch and heat the hub, then check tightness and hit it again.

[blinddog]

I loosened the nut a few turns but left it on for that very reason. I'm going to pull the boat home and heat the hub to see if that helps. Otherwise, I'll have to take it somewhere.

[TallSkinnyGuy]

It's unlikely you won't be able to get it off after applying some heat to the hub of the prop. Just get some pressure on it with the prop puller and heat the hub until it pops loose. I used an acetylene torch and it took about a minute of heating the hub to get it loose.

[blinddog]

Thanks everybody - the Master Craft place got it off this morning. They also checked the shaft and it's straight. They are going to replace the damaged bushings, check the strut, and align everything so I should be good to go. Only issue left is it's going to take 7-10 days to get the prop fixed so my only backup is a 13 x 12 three blade. The one I pulled off is a 13 x 14.5 four blade. Shaft is 1.125" as it turns out and the backup fits that. My only concern there is running the rpms up too high with my son @ 36 mph. I guess I won't know until I try it. Only other option is to try to find a more suitable backup and get it quick so we can ski Memorial Day weekend.

[UWSkier]

13x12 on a 1:1 Malibu such as a Response LX typically spins 100:1 RPM to MPH so 36 MPH is roughly 3600 RPM. If your boat has a 1.26:1 redux, you're looking at 4500-4550 RPM give-or-take a bit for hull drag. Probably fine for a few sets, but that boat is going to feel REALLY firm. Better off seeing if you can trade in your spare prop for one that's more appropriate for your application.

[jjackkrash]

I just ordered a new spare ACME prop for the new boat and a weekend-saver kit from WakeMakers. They shipped the next day and got it here in two days.

 

https://www.wakemakers.com/propellers

 

https://www.wakemakers.com/prop-accessories

 

I always keep a proper replacement spare prop just in case. When one prop gets dinged off it goes to the repair shop and the spare goes on and stays there until it gets dinged and then the repaired prop goes back on. And so on. I can't remember the last time I had any down time because of a prop ding.