Reconsidering WOT Prop Weighting Ballast or No Ballast:

[Gazmn]

I posted this question on 2 Evinrude boards - hence the Splainin'

But the question of what weight should we prop for is legit. Thoughts?


" I'll be using a Pontoon 115HP on a waterballasted motor sailor [ A what?]
A MacGregor 26X Powersailor - bear with me a moment. My boat dry, unballasted weighs about 3500lbs. This would be it's weight for motoring & normally what I'd use to prop boat for WOT.

When sailing you open a valve at the transom & in comes 1400lbs of water for ballast. Making boat weigh ~ 5000lbs. You close valve once full. While a bit tippier than a reg lead Keel boat this feature, along with a semi displacement flat bottomed hull, allows for motoring speeds up to 24mph, while unballasted.

When it's choppy or snotty I'll motor with the ballast in because it helps to center the boat & give a calmer ride. To de-ballast you open the valve and motor off over 8mph and the ballast will dump in 5 mins depending on speed.

Here's my question: Should I prop for WOT with the ballast in? To not lug the motor for slower speeds in chop while ballasted

Should that 1400lb weight difference concern propping? How?

I probably motored with ballast in ~15 - 20hrs last season due to conditions.

This is part of the reason why I went with the pontoon line. As sometimes you'll run with 1 or 2 people & sometimes with 10, on a pontoon. How should this affect prop choice?"

[mastreb]

You prop for un-ballasted WOT operation. The reason is that if you prop for ballasted weight, and then run un-ballasted, the engine could rev over max RPM (old motors) or would be power limited by the ECU to max RPM (new motors). Hitting electronic limiters is better than not hitting them, but not great because you're leaving power on the table. Also, propping this way gets you to maximum speed, which I know is a concern for you

When you do run ballasted at WOT, the engine will be working hard and not getting to max RPM. That's perfectly fine. Engines are perfectly fine laboring, its much better than they are running faster than max RPM. You won't be able to eek out every last hp this way because you can't get to max RPM, but it's the safe way to go.

For the same reason, your boat should be as empty as reasonable when you determine your weigh for propping or when you test props. That means just you, no consumables, empty tanks. But everything permanently installed should be in place. Essentially, you want the boat as light as it will ever be, but no not lighter. Then prop to the absolute max RPM, knowing you'll likely never get there.

Or just get a prop for each and a quick nut so you can swap them when you ballast Hey we're mac sailors, right?

I don't know why nobody has ever come out with a variable pitch prop for outboards so you can go WOT at any weight and then trim pitch to get to max RPM. That would solve 90% of propping issues. Been doing that on aircraft for decades. I guess really only Macs have this problem.

[bobbob]

Didn't know a Mac 26X could support such a high-HP outboard - thought only Mac 26M's were recommended to go above 50-60HP?

[Gazmn]

You know I've probably brought this up before. Its still a long winter. Here are the answers I got from the Evinrude boards:
Fr. Etec Owners group:

You are right, it would be like propping for a pontoon boat or any type of cargo craft where the carrying weight changes a large amount.

Load down the boat as much as you can and prop for a minimum of 5500 rpm. I'm sure you have a tachometer to watch that the rpms do not go above 6000 with a light load. I am assuming that a prop with either a 9" or 11" would be the place to start.

Fr E-Nation, Pontoons & Leisure:

suggest propping the motor as close as you can to the redline, 6000 rpm, with a very light load, then check the rpm with full ballast, fuel, gear, and passengers aboard. Make sure the heavily loaded rpm is at or above 5500.

If you have to decrease pitch more to get the revs up to carry the heavy load, that could cause a bit of overrevving with a light load. Just watch the rpm when running light and do not exceed 6000.

So, I think it's the same answer but given from dif ends of the equation.

[Gazmn]

Fr. Mastreb:

you want the boat as light as it will ever be, but no not lighter. Then prop to the absolute max RPM, knowing you'll likely never get there.

So, you sound like E-Nation. & this is what I always did with the 90hp. But I asked because once loaded down, or ballast in I would never see my top RPM & wondered if I was actually lugging the motor with regular usage or sometimes running the motor with the ballast in for choppy conditions.

Re: Bobbob:
I have a non warranteed & have always broke the rules

[kadet]

Should I prop for WOT with the ballast in?

You should prop for whatever is most important to you.

Speed?
Economy?
Low Speed handling?

Everything is a compromise.

Or just get 2 props. One for day tips and one for overloaded holiday time like I did I have an 11" and a 13" pitch.

Though I must admit I am never lightly loaded these days even on day trips and I sail more than ever and almost never go WOT any more so the 13" sits in the bilge as a spare these days.

[yukonbob]

Re: Bobbob:
I have a non warranteed & have always broke the rules

This is interesting as it came up last year in a court case here involving a local dealer / boat shop and the death of a local RCMP (Mounties) where the prosecution tried to hold the dealership and individual mechanics liable for his death (large motor on a homemade aluminium boat from what I remember) Thankfully the judge ruled they were not liable and the other factors lead to the death of the officer (no life jacket and full utility belt / police gear on). Warranty is not the issue with putting a larger engine on than the boat was designed for; its all about liability of the person who designed the boat and when you exceed it, you or your dealership potentially take on that liability. Just foo for thought.

[kadet]

its all about liability of the person who designed the boat and when you exceed it,

Or their lack of liability if they can show the larger motor was the cause of the tort.

This only comes into play where the larger motor was the cause of the actionable claim. E.G. extra weight and power caused the transom to come off and sink boat or made boat go faster than design limits and it flipped etc..

Most boats in OZ previously only had a transom weight limit only recently has an upper HP limit also began to creep in (newer motors lighter and more powerful?) due to the introduction of mandatory build plate information. Again these are recommendations and design specs not law. The law actually says for us here.

Note: ABP’s, are mandatory on all new pleasure craft with the exception of:

An amphibious vehicle; a canoe, kayak or surf ski or similar vessel designed to be powered by paddle; a rowing shell used for racing or rowing training; a sailboard or sail kite; a surf row boat; a hydrofoil or hovercraft; a race boat; a sailing vessel; a submersible; and an aquatic toy.

A sailing boat with an auxiliary engine is exempt from the requirement to have an ABP fitted.

In the case quoted the judge made the correct ruling if the cause of the death was no life jacket and the way the boat was operated and not the oversize motor were the causal factors.

BY fitting a larger engine you are accepting responsibility to properly operate and have it fitted correctly. But then again as captain this is always your responsibility regardless of engine size.

The same as people who mod cars by beefing their rated horse power with add-ons.

It could also make it harder or more expensive to get insurance and if you have not declared the modifications give the insurance company an out in paying any claim.

****ALWAYS CHECK YOUR LOCAL LAWS AS THEY VARY****

[Gazmn]

Bob,

I always appreciate your comments. You "Mac" on what is - the last frontier. & you certainly have pointed out an issue that concerns all Captains & boaters. & as a Captain, I'm cautioned, as I always have been. However, I don't want my quote to be misunderstood. It was said in jest.

I have spent over 20 years protecting life & property, in the City & on the water. & have always been considered part of the solution rather than the problem. Inspite of the HP & bravado, I don't boat fast or careless. There would be Hull to pay. My former Capt in 58 Eng. Now runs FDNY Marine 1. Marine 4 is stationed in Bayside, where I boat & I Know & worked with many of them.

Warranty is not the issue with putting a larger engine on than the boat was designed for; its all about liability of the person who designed the boat and when you exceed it, you or your dealership potentially take on that liability. Just foo for thought.

When is a Capt Not liable for his boat & passengers

[yukonbob]

Bob,

I always appreciate your comments. You "Mac" on what is - the last frontier. & you certainly have pointed out an issue that concerns all Captains & boaters. & as a Captain, I'm cautioned, as I always have been. However, I don't want my quote to be misunderstood. It was said in jest.

I have spent over 20 years protecting life & property, in the City & on the water. & have always been considered part of the solution rather than the problem. Inspite of the HP & bravado, I don't boat fast or careless. There would be Hull to pay. My former Capt in 58 Eng. Now runs FDNY Marine 1. Marine 4 is stationed in Bayside, where I boat & I Know & worked with many of them.



When is a Capt Not liable for his boat & passengers

Just putting it out there is all.

Transom failure is a real thing but the big concern is your insurance being voided upon discovery of being overpowered (your adjuster or someone else's). You may be able to pay a premium on your insurance or have it re-rated with a higher HP if possible.

Selling also becomes an issue; If you were to sell an overpowered boat to someone and they crashed it and the buyer could prove (or you couldn't prove) that the max HP rating was exceeded and not mentioned at the time of sale you could be liable. You may also run into issues if boating outside your normal stomping grounds in an area with stricter laws and leave you open to fines.

So unless you can have someone re-rate your boat with a higher HP and ensure your coverage be prepared to hand your keys over if you rub another boat coming into dock.

[mastreb]

I kind of like two props here. You're generally going to know what you want to do and what conditions you're going out in, and when you get caught unaware, just watch your throttle. Good grease and a reusable cotter pin makes this easy.

[Seapup]

My bet is you don't see that big of an RPM difference between full and empty ballast with the larger displacement motor and a heavy boat. ( assuming you keep it well loaded while on a mooring all season) I had a 1000rpm difference when my boat was stripped totally empty first testing the 90, once it was loaded for use it was less than 200rpm ballast/no ballast difference. (about an 8mph difference from stripped too)

[Seapup]

I kind of like two props here. You're generally going to know what you want to do and what conditions you're going out in, and when you get caught unaware, just watch your throttle. Good grease and a reusable cotter pin makes this easy.

I have that change down to about 2 min...

I was swapping these 4 back and forth yesterday...all have the same pitch but different fin design and all run totally different

[Gazmn]

I Agree with you guys regarding good grease & switching props for conditions.
That's a nice collection you have there Alex. I had a bit of a collection too. & now find out that I'm gonna either have to rehub or just invest in newer props. This lower unit is a much beefier V6 model, 15 spline. Yay

It also made me think about what may have been my problem. Purchase used prop - probably worn hub Oh the dangers of buying on Ebay... It's not every prop in my collection but that could also account for my prior lower performance issue.

I had good torque with a 4 blade, though. I'm thinking more the 4 blade & looking for some stern lift.

Re: the insurance YB, I use BoatUs & will inquire about coverage issues. My 90 was covered, no problems, including the Bahamas - I'm hoping for the same.

the big concern is your insurance being voided upon discovery of being overpowered (your adjuster or someone else's). You may be able to pay a premium on your insurance or have it re-rated with a higher HP if possible.

I didn't have a problem with the 90 as we do not have a plate / motor restriction posted - period. That's my story & I'm gonna stick with it. I've had a 90HP for 8 years with no issues or stress & have used backing plates & Common Sense all this time. That's not gonna change.

I keep an eye on the throttle. I don't come in Hot & I'm not out doing donuts & figure 8s.
I just wanted more bottom end to push this tug more efficiently through the water.
To Rephrase ZZ Top: "...I ain't askin' for much... Lord, Take me downtown - I'm just lookin' for some "Torque" "...
["Tush"]

[Wind Chime]

Would a cavitation plate hydrofoil effect WOT performance?
http://www.stingrayhydrofoils.com/stingray-classic/