Sensenich help...

[radtech]

So, I rebuilt my 472, bored .030 over, 120 RV cam. I'm currently talking with Stinger about purchasing a 1.73/1 sort drive box. I would like to contact someone knowledgeable from Sensenich to decide what the best 3 blade prop would be to put on my boat. I am assuming I will need about 10k to do the gearbox and prop. Who would be the best person to talk to about it

 

[Deano]

The best person would be the next guy after me to tell you you have to much time and money invested to use less than a 2.09 gear.
A 1.7x gear is for a stock, tired original antique that usually has an equally tired and decrepit valve train.

This is almost so simple that it's hard to explain.
Sensenich Super Wides push like a beast and don't require stupid power until you try to spin them past 2 grand.
A 2.09 gear will let you spin your engine at a calm, cool and collected 4200 RPMs and still attain that end.

The FAR BETTER question for Darin would be "What diameter of the later model S blades do I want to use with my 2.09 gear to enable me to adjust my RPMS between 39 and 4300 rpms."

Brother, I don't want to sound harsh in any way, but you keep shooting yourself in the foot at every Cadillac turn.
Given the time and money you have already expended, imho, it's way to late in the game to "settle" for what will just work.

You do NOT need to spin monster engine RPMs to attain monster push with that engine,
but you DO want to use all the gear you can to best attain that end.

 

[radtech]

Thank you for the advice, Deano. And you are correct. I HAVE shot myself in the foot many times over the years. I had 1 other person (the guy that has helped me physically build my engine and do the work on my boat locally) that told me a couple years ago to get a 2.(something)/1 gearbox if I was planning on doing it. Every other person has said do 1.73/1. And, doing the math, to attain max power and torque, to get 5000 rpms out of the engine and 2800 on the prop it figures to 1.78. That is why I was looking at 1.73. I appreciate your advice and knowledge on the subject, and agree that it is probably best not to have to push the engine to it's limits to achieve what I want to.

In my younger days, I was much more wild and spent quite a bit of time finding myself stuck on sand bars, or islands that I foolishly decided to drive across. My biggest concern these days is to be able to go to places like BS Hill, or wherever and park without having to have help to leave. I am speaking with Stinger tomorrow about ordering a gearbox and will heed your advice. Thanks again, Deano for taking the time to share your experience and knowledge. Hope to meet up with you one day soon on the trail!

 

[Deano]

Radtech, I had no idea you were figuring on turning your engine up to near 5 grand. If your valve train is capable of doing that for the long term, you could disregard my comment about limiting your RPMs to 4300. I don't know anything about your valve valve train, but I don't think an RV cam is going to pull that far anyway. Short of having installed a shaft rocker system, 5k wouldn't be very prudent anyway.
The thing to bear in mind is that just because you are running more gear, does not mean you have to turn more RPMs. It simply means that the selected prop needs to be productive while spinning less rpms. I always shot for quiet and the original Super Wides fit that bill largely because they ran at a lower rpm than most alternatives. The old Maximus blades also worked well at 2k rpm, although they weren't nearly as popular.

I'm not familiar with the specs of their newer blades that replaced the older S blades so that is a conversation you want to have with Darin.
With the 2.09 gear, having a wide blade prop that pushes effectively at 1900-2150, would translate to about 4000-4600 RPMs. Even
without knowing specifics about your boat or build, I will still say that given the correct prop, a 2.09 would leave less on the table than a 1.73.

 

[radtech]

That is where I am getting confused, deano. I am, unfortunately, getting very antsy because my boat has been down for 3 1/2 years. I need to figure out what the best combo is. I figured prop speed at 2800 rpms, so figuring 5000 rpms on engine and 2800 on the prop, it would be 1.78/1 I had no idea the 3 or 4 blade props were made to turn that low, so I was scratching my head at the 2.09/1. I seem to need to back off for a minute and get it all figured out before making this big a purchase. Also, the sensenich blades I have looked at are 80" and up. Won't fit my current cage, though because the builder built my hull wider than I wanted, I will have to modify my trailer and cage as well. Gonna have to do some measuring and figure out what I can do and go from there.

 

[radtech]

Radtech, I had no idea you were figuring on turning your engine up to near 5 grand. If your valve train is capable of doing that for the long term, you could disregard my comment about limiting your RPMs to 4300. I don't know anything about your valve valve train, but I don't think an RV cam is going to pull that far anyway. Short of having installed a shaft rocker system, 5k wouldn't be very prudent anyway.
The thing to bear in mind is that just because you are running more gear, does not mean you have to turn more RPMs. It simply means that the selected prop needs to be productive while spinning less rpms. I always shot for quiet and the original Super Wides fit that bill largely because they ran at a lower rpm than most alternatives. The old Maximus blades also worked well at 2k rpm, although they weren't nearly as popular.

I'm not familiar with the specs of their newer blades that replaced the older S blades so that is a conversation you want to have with Darin.
With the 2.09 gear, having a wide blade prop that pushes effectively at 1900-2150, would translate to about 4000-4600 RPMs. Even
without knowing specifics about your boat or build, I will still say that given the correct prop, a 2.09 would leave less on the table than a 1.73.

I responded earlier, but missed the part about the valve train. I'm not really sure what the engine place put in, but they replaced all the valves and valve seats along with new 10/1 .030 over Keith Black pistons, New timing set, etc

 

[Deano]

I have to agree that you should stop, and design a plan to properly identify all the pieces so they work together.
I mistakenly figured that by now you had already done this. You were thinking correctly that your engine and gear need to work together to spin the prop at the RPMs where it would be the most productive.

I fear though, that you (and/or them) may have overlooked the intrinsic design limitations of the stock valve train. There have been volumes written here specifically about that. The biggest & foremost limitation by itself, was the WEAK and SOFT valve springs. They were only 65 lbs closed on the on the seat, which worked ok in a land barge or in a direct drive. That pressure becomes woefully inadequate for turning more towards 5000k though. If your 'engine place' simply used STOCK factory replacements, you NEED to severely limit your RPMs and your 1.73 plan will be your better bet. I thought that when you rebuilt it this last time, you did so with the intention of running the gearbox. My bad.

While your math was good figuring your ratio (ie, 5000/2800 =1.78), where you erred, was making the assumption that your engine would turn 5000. A stock valve train will not stay together, nor is an RV cam likely to pull for that long. It may spin that fast long enough to set the prop pitch, but it would not exhibit the longevity that would be expected from a fresh rebuild.

Maybe they DID sufficiently upgrade your springs, replaced the rockers, & Ts, and thoroughly checked the geometry, and I'm being overly cautious on your behalf. I believe there is no doubt that it would be well worth the time and effort to make that confirmation before committing to a gear ratio and/or prop though.

Which KB pistons did they put in it?

 

[radtech]

All valid points, for sure, Deano. The only thing as far as the KB pistons that i can tell you with certainty is that i ordered the .030 Keith Black 10/1 pistons from CAD company. I have begun my research already by contacting sensenich. I am told that using the 1.73/1 Stinger, I can run a Sensenich 78" 3 blade JR at 42-4800 rpms (engine speed) to gain more than the power I need to break loose on dry ground. That is the only high end I require, as I will only be cruising any other time. I may have neglected to mention I don't plan to run a ton of dry ground, run over trees, etc. Just want to be able to pull up on the hill and not have to have help to get back to water. I truly appreciate your help so far and am always fully willing to listen and take any more advice from those more knowledgeable than i

 

[OneBFC]

JR blades have minimal low prop rpm thrust in my experience. I think that they would be a poor match for a broad power curve motor such as yours.

Sure, they will work fine. But your cruise rpm will be way higher than it would be otherwise with a different prop choice.

I would obviously run a Maximus, but a similar wide blade from other manufacturers likely return reasonable results.

When I tried JR blades it was like I lost 2/3 of my RPM thrust wise. Top end was all the same, but mid and low were very noticeable less. I think its well suited to an engine that makes torque at higher rpm like a stock LS does.

Good luck!

 

[radtech]

JR blades have minimal low prop rpm thrust in my experience. I think that they would be a poor match for a broad power curve motor such as yours.

Sure, they will work fine. But your cruise rpm will be way higher than it would be otherwise with a different prop choice.

I would obviously run a Maximus, but a similar wide blade from other manufacturers likely return reasonable results.

When I tried JR blades it was like I lost 2/3 of my RPM thrust wise. Top end was all the same, but mid and low were very noticeable less. I think its well suited to an engine that makes torque at higher rpm like a stock LS does.

Good luck!

So, the maximus is what company? I definitely want to discuss all options and make a proper plan before spending the money this time. Also have to measure my cage and new hull to see where I will be at with my blade width. May wind up tearing my cage apart to rebuild it to a more usable width. Thank you, brother!

 

[OneBFC]

BLADES | Carbon Concepts

www.carbonconceptslwf.com

I have run those and many others on my 2.0 liter ecotec since 2012. I always come back and stick with the Max. It just has the widest thrust curve in my experience.

It will cruise from low 2000 and still provide plenty of top end. The 3 blade 80 inch on mine with a 2.38 Ox has pushed my boat to 96mph before I got too scared on the edge of lake cypress on a 40F morning.

If my puny little 122 cubic inch engine can swing it, certainly your monster can

Looks like my signature got wiped out here at some point....so, I will just leave this link here to my, now getting old, youtube channel so you can see for yourself. Boat weighed about 2000lbs loaded before it went on diet with the Simpson air ride. Clocks in at 1430lbs dry now.

https://m.youtube.com/@1bfc

Here it is at polluted on a hot summer day when the engine was all stock parts and made about 330hp. Oh. And a 76 inch version of the same 80 inch Max i run today.

prop is a big part of how this boat runs..

Ok, i need to call up CC now for my commision check i suppose..

good luck again sir!

 

[Deano]

Carbon Concepts is what Water Walker was before David Wine exited the company. I agree with Russ, the Maximus blades would work very well for exactly what you are wanting to do. It looks to me like your other viable alternative would Whirlwind's CarbonMax EX blades. I have no experience with them but throw that out there so you can research all your options. If anybody reading this is running them, I'm sure they will comment. Again, I am in complete agreement with Russ.

Just because the conversation has shifted directions, don't forget about your valve train. Having that correct should be viewed as a prerequisite to doing anything being talked about here, as it is more important than what propeller you ultimately decide to use.

 

[radtech]

I'm currently at work and have tried several times to respond to recent messages. They're keeping the ol Radtech runnin. I will certainly give it some thought and respond tomorrow when my 8 day xray nightmare will be over for 4 days. I appreciate all the advice

 

[radtech]

So, a little update at where I'm at. After the previous discussion with Deano, and certainly keeping in mind that I am unsure of the valve train that was installed in the rebuild, I spoke with Darin at Sensenich and Sharon at Stinger. (This was before the last comment from Onebfc) I was of course having my after work bourbon and cokes to prepare for sleep so I could work that night. I ended up erring on the side of rpm caution as I do not want to rebuild anytime soon. So I bought a Stinger 1.73/1 gearbox which will be here today. After Onebfc's comment, looked up the Maximus blades and they are not meant to work with my gear ratio. I will be making a few runs today to get measurements on my cage, boat, etc and am going to research the falcon, which is made to run with my box, and the corresponding Sensenich blades to assess which might be the better prop to go with, as well as any other suggestions that I might receive, before purchasing a prop.

 

[Deano]

Very little variance at the top end with between these set-ups.
Spinning 4250 engine rpms ->
- with Falcons and 1.73 gear = 2456 pRPMs
- with Maximus and 2.09 gear = 2033 pRPMs

The discernible difference would be the Falcons will render you a little higher cruise rpm,
where the Maximus would provide a little quicker push at a lower RPM.

Either way beats the shit out of shaking the rake of a direct drive.
You will finally have that big grin you been after. Congratulations !

 

[radtech]

Very little variance at the top end with between these set-ups.
Spinning 4250 engine rpms ->
- with Falcons and 1.73 gear = 2456 pRPMs
- with Maximus and 2.09 gear = 2033 pRPMs

The discernible difference would be the Falcons will render you a little higher cruise rpm,
where the Maximus would provide a little quicker push at a lower RPM.

Either way beats the shit out of shaking the rake of a direct drive.
You will finally have that big grin you been after. Congratulations !

Thanks, Deano! That is the kind of info I need now. Definitely moving in the right direction. I measured the place where the cage will mount on the boat and it is 92" wide at that point, so the matter of trying to cram a smaller prop in is now mute. I will have to either tear my cage apart and reuse what I can to build a new cage or scrap it and build a whole new cage. Haven't made it up to where my rigging, cage, etc are stored yet to measure all that stuff

 

[Slidin Gator]

Either way beats the shit out of shaking the rake of a direct drive.

I use my rudder on my direct drive, works 99% of the time. But sometimes the "wait a minute" vines take over and I gotta break out the secret weapon.

Rad,
You got an antique valvetrain and do need to keep your revs in check. I think Deano summed up the performance differences well for your setup. The only thing I would add is the 1.73 locks you into the power level you are at now vs. the higher gear giving room for engine/valvetrain upgrades in the future.

I suggest 5 more Bourbon's to decide if you want to stop/backup or keep mowing.

 

[radtech]

I use my rudder on my direct drive, works 99% of the time. But sometimes the "wait a minute" vines take over and I gotta break out the secret weapon.

Rad,
You got an antique valvetrain and do need to keep your revs in check. I think Deano summed up the performance differences well for your setup. The only thing I would add is the 1.73 locks you into the power level you are at now vs. the higher gear giving room for engine/valvetrain upgrades in the future.

I suggest 5 more Bourbon's to decide if you want to stop/backup or keep mowing.


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Lol I hear ya,brother! I have a lil secret weapon of my own. Got the full series of kobalt power tools, including the 80 volt chainsaw and 40 volt pole saw. Gonna make mounting hardware on the boat to keep them out of the way just in case. Ya never know, but I don't INTEND to get into a position where it is necessary. As above stated, my days of attempting to climb trees and jump random objects in the water are over. I'm comfortable with the idea that a little gear reduction will do what I want to do, which is pull up on dry, then pull off without help. Just gotta decide which would be the best prop for that gear between Carbon concepts, whirlwind, and Sensenich. Looking at the 3 blade falcon, JR, and the carbon max, though so far, the carbon max appears to be all made for higher gear ratios. I'm not gonna go for the prop til I can thoroughly investigate all 3 options.

 

[Slidin Gator]

We on the right track!

 

[radtech]

We on the right track!

Damn right, brother!!! Gonna be buying a prop before the month is out, then it will be time to get it all together!