Lower unit longevity

[Powerplay25]

I'd like to hear some opinions on lower unit longevity in regard to running a 3 blade prop as opposed to a 4 blade. Specifically on the sportmaster in a surfacing application.

Is a 3 blade that much tougher on the lower than a 4 blade?

[mcyama]

It is a game of Russian roulet. There are pro's and con's too both. So what is the true issue, breaking gears? The higher the ratio the stronger the gear. Let me know the rest of the story. Thanks Martin

[Ro Yale]

I'll tell you something that definetly makes them last longer. First mycronite the gears then cryo everything. Works!

[Powerplay25]

It is a game of Russian roulet. There are pro's and con's too both. So what is the true issue, breaking gears? The higher the ratio the stronger the gear. Let me know the rest of the story. Thanks Martin

I have not had any problem at all with breaking gears. I currently run Bravo props. Was thinking of going to a set of Choppers.

I've heard that 4 bladed props are much easier on the lower as they are better balanced then a 3 bladed prop. If going to a 3 bladed prop means I'm going to start blowing up lower units then I'll just stick with the 4 blade.

The motors are set very high on my boat and I do run out in the ocean and they will occasionally break loose. You could make the alternative argument that a 4 bladed prop loads the lower more upon reentry then a 3 bladed prop will.

I'd like to hear from someone who has tried both.

[Ted Stryker]

Get some fat shaft Sportmasters that are factory healthy or set up well if rebuilt, good 4-blade Hydromotives or such, use synthetic fluid and change often, and always start the engine in gear... As Ro Yale said, I have heard on numerous occasons about the benefut of cryo'ed internals... That's about all any of Us can do, the rest is in the cards...

[wideglide55]

I changed to a 4blade and never took it off after that,so much less vibration and slippage as opposed to a 3blade that the extra 2-3 mph just ain't worth it,all that vibration from the 3blade has to take its toll after time.I'd leave them alone if I were you.The RE-4 28 raised my cruise speed and mileage over the RE-3 29 and only lost 2-3 mph,so much smoother and much better hole shot.

[Powerplay25]

Get some fat shaft Sportmasters that are factory healthy or set up well if rebuilt, good 4-blade Hydromotives or such, use synthetic fluid and change often, and always start the engine in gear... As Ro Yale said, I have heard on numerous occasons about the benefut of cryo'ed internals... That's about all any of Us can do, the rest is in the cards...

Already running fat shafts. Again breakage has not been an issue.


I changed to a 4blade and never took it off after that,so much less vibration and slippage as opposed to a 3blade that the extra 2-3 mph just ain't worth it,all that vibration from the 3blade has to take its toll after time.I'd leave them alone if I were you.The RE-4 28 raised my cruise speed and mileage over the RE-3 29 and only lost 2-3 mph,so much smoother and much better hole shot.

That's what I'm referring too. The vibration with a 3 blade compared to a 4 blade. I know I'll pick up a lot more speed with a pair of labbed 28" Choppers, but will they shorten the life of a lower that much? Is the vibration that much more noticeable?

[HighVelocity]

Dave,

The question I have is why 3 blade props vibrate at all. If the prop is balanced to zero, why would it vibrate???

As I see it, 4 blade props are going to cause more wear and tear because they grab harder after you break loose and re-enter the water. Less slip means the shafts and gears are taking more shock/load.

You know when Bill went from 4 bladers to 5 bladers he blew a drive that same weekend. He has to be way more careful.

Dave, I know you know this, I'm just not sure where you are coming from on this.??? I run a 3 blade prop, my boat doesn't vibrate. Maybe it's your yellow gel-coat...lol

[sschefer]

The best balanced and performing wheel is a single blade continous screw. I run one in my North River.. Yep, it's a jet. The problem with that concept on an outboard is your reverse gears don't do anything.

Three blades are not necessarly less balanced but do have more tendancy to cavitate than 4 blade screws and therefore produce higher levels of vibration. Theres more reasons but you can read about that when you start picking one out.

I own enough props to cover half the back wall in my 3 car garage. For the type of running the OP does, I'd suggest staying with the 4 blade and would even go as far as to recommend the Stilletto Bay Runner II as the smoothest running, best performaing 4 blade I've come across.

[whipper]

Gearcase should last for many many years with no trouble if maintained properly. New impeller every year or twice a year. Seals checked and new oil every month or so along with inspection of oil. Thats if your running a few times a week at least. Three blades are faster on light boats but ussually only about 1mph if any differance at all. Sometimes 4 blades are faster. It all depends on the prop and who worked it. I went away from 3 blade props because I found faster 4 blade props for my GS. It took a long time to find 3 special props but I have them now.:thumbsup: On your Powerplay I would agrue that 4 blades will be faster than 3 with twins if not just because of your displacement.:thumbsup: This has been proven many times. Its also worth noteing the last couple of years some of the winningest drag racers are useing 4 blade props aswell. With new cuts for 4 blade props available today I would have your 4 blades worked and the differance would be over 3mph. For me Ive seen over 5mph!! Lighter boat= more differance mind you. Talk to Todd at Hydromotive about this. Hes experamented with prop setups of hundreds of boats in your size range with great results. Stock prop to stock prop there would be less differance than worked.
I also agree with you on the 3 blade VS 4 Blade to an extent. And with the 5 blade your friend mentioned on the other guys boat I believe that also. I think 4 is the perfict number. Just my opinion.

[Powerplay25]

Well I spoke to Smitty from Wazzup Racing tonight. He just installed a new prop shaft in one of my lowers and went through the whole thing and tightened it up.

Smitty agreed that there will definately be more vibration from running a 3 blade compared to a four blade. However he said I should not see much of a difference in wear and tear on the lower unit in running a 3 blade. He said it would be more pronounced if I was running 2.5's.

At the very end of the season I switched my lowers to spin the props inward and now I'm getting too much stern lift with the Bravo's I'm running now. He suggested I could send them out to get more cup added to them and it should solve the problem. Decisions, decisions....

[HighVelocity]

Dave, That's a deal right there. Just think if get those brovos tuned up for your boat, you should save some bucks right$? Smitty has the inside track when it comes to set-ups, I would go with his recommendation.