Thinking of buying or upgrading to new boat?

[Ronje1]

Hello

Thought that some may be interested in the interactive XL sheet I mentioned in trying to work out some of the pros and cons of such a move.

One of the things that DOESN'T change in those deliberations is the power to weight ratio of the basic installation that you choose. That p/w ratio gives you the very basic weight figure of the bare boat and the motor. As you put more gear into the boat, the weight that each horsepower has to push around gets higher.

The p/w ratio is not going to get any better than the basic combination of boat/motor that you choose.

Your preferred choice of motor brand can easily be factored in by its technical specs which are readily available as are the boat specs. It may be that there are valid reasons for motor choice but at least the xl sheet will tell you what price you pay (or advantage that you get) in terms of power/weight ratio in doing so.

Lucky Phill and Steve combined to change the types of files allowed to be uploaded to include an interactive sheet like this.

Thanks to both of them.

How the sheet works is that YOU can enter details in the yellow squares, the calculations are done automatically by the sheet and displayed in the red squares.

The RHS block of yellow squares are "add-ons" for convenience in the overall cost price calculation.

The sheet is by no means finished as I'm sure most will find bits missing that they think should be included. Happy to do those amendments.

​Trouble uploading. Get back shortly.

[ranmar850]

It could be an interesting thing to play with, for sure. I used to do a lot with Excel, in regards to managing data, actually did an interactive spradsheet when I was a commercial fisherman to see if a particular lease deal would be viable with all inputs variable. Cost of leased pots, average catch price return, fuel, bait, gear replacement, crewshare, fixed inputs. Not hard, really, with some basic Excel skills. The idea came about after my bank gve me one they had developed for that specific purpose ( leasing craypots in the WA Rock Lobster industry) . One of the cray factories had one as well. These are crap, I thought, so I went to work. A few days later, I had a good working model. Both the bank and my accountant ended up using it, or at least distributing it with my permission, after they were shown.

I also have one I did when I bought my last new boat, which was just a way of keeping track of costs in an honest manner, right down to ss bolts and screws, and comparing value of having the dealer/shipwright do some facets of the work vs me doing it.

But there is one caveat with all this--boats are highly personal things, even more so than cars, IMO, and different hull/motor combinations can feel quite different , regardless of basic HP ratings. Can't put a dollar value on it, really.

[NAGG]

Start with the biggest motor & work your way back -

I'm still to see or hear of anyone complaining about having too many ponies on the back of their boat …… specially not a fishoe.



Chris

[gazza2006au]

Seems to be the aussie way Chris no one ever complanes about more horse power lol im surprised we dont have max speed limits on the water some skeeter boats friggen fly along

Sent from my SM-G900I using Ausfish mobile app

[stevej]

Boats are designed to work best with max hp.
as soon as you starting reducing hp you are making a compromise in boat performance

and at least in nsw there are so many speed restriction rules.
someone under 18 on board max 60 knots
recreational skiing 60 knots
and the arse covering kicker where no speed limits are posted travel at a safe speed to avoid a incident. The fella doing 70 knots in his skeeter who hits the fella in his tinny Doing 20 will be the one getting pinged for excessive speed

[scottar]

Boats are designed to work best with max hp.
as soon as you starting reducing hp you are making a compromise in boat performance

Yes and no. Depends what you are doing and what other penalties come along with the max hp - transom weight being a big factor but engine torque curves playing a part as well. On smooth water it's not so much of a consideration. Spend your time offshore though and the results can be somewhat different depending on what your definition of "performance" entails. My own rig would be a better performing boat offshore with a 150 than the larger block (and thus heavier) 200 that is on it. I also know an extremely experienced offshore skipper who at one stage went from a 200 to a 150 HPDI Yamaha on a 625 Cruisecraft. The engines were the same weight but for typical offshore work the 150 used less fuel and was nicer to drive because it was at a better place in it's torque curve. The only place these particular combinations really lost out was in calm water top speed. Maybe a slight reduction in hole shot but nothing of significance.

[stevej]

I was more thinking along the lines of smaller boats
My 420 renegade for example which i s50 max but dealers will fit them with a 30 to meet a price point or a old timer saying that will be enough and will be more economical

lots of apples and oranges in the comparisons as you say
someone who runs a nasty bar but then fishes max 15mins away might just pure grunt to get across the fella who doesnt run bars way not want the same thing etc etc

[NAGG]

Yes and no. Depends what you are doing and what other penalties come along with the max hp - transom weight being a big factor but engine torque curves playing a part as well. On smooth water it's not so much of a consideration. Spend your time offshore though and the results can be somewhat different depending on what your definition of "performance" entails. My own rig would be a better performing boat offshore with a 150 than the larger block (and thus heavier) 200 that is on it. I also know an extremely experienced offshore skipper who at one stage went from a 200 to a 150 HPDI Yamaha on a 625 Cruisecraft. The engines were the same weight but for typical offshore work the 150 used less fuel and was nicer to drive because it was at a better place in it's torque curve. The only place these particular combinations really lost out was in calm water top speed. Maybe a slight reduction in hole shot but nothing of significance.

That's interesting considering that there normally isn't a massive difference between min & maximum HP ………… in the smaller & mid HP - it can be negligible .

There is SFA difference in weight between the F150 & 200 Yamaha …. & on checking - The F150 yammi is actually heavier than the F200 .

I had a 70hp Yammi originally on my Seajay barramasta - I changed to a 100 yammi and it was a much improved boat ……. I asked if there was the possibility of adding the F115 …. which was declined . personally with the weight loss of the 115 - it was probably the ideal motor for the boat …… I certainly felt that the hull wanted more

Chris

[catshark]

some semi displacements hulls work fine on lower HP. deep vees however another story

[scottar]

Yep - depends on the boat and four strokes may be different again too and then there is always the point where a motor is too small for a boat and the performance does suffer. The Victory as an example, would basically run with anything down too a 135 Honda. It was designed around the 150 to 200 small block V6 OMC motors but would carry right up to the larger V6 fourstroke Suzukis and Yamahas. The 225 Honda was a bit over the maximum transom weight but could be fitted with insurance company permission. This gave a difference of somewhere in the vicinity of 80 odd kilos in transom weight between all the available motor options. The big engines are definitely quicker but all other things being equal, the lighter engines made for a much more enjoyable boating experience (apart from the fuel burn) in rough weather. The engine that suited best really did depend on the outcomes required for the owners usage.

The Cruisecraft was IMO a torque curve thing. The 200 was at a point it just wasn't quite happy when going slow enough for rough weather boating. The 150 however was pulling more revs for the same boat speed courtesy of needing a slightly lower pitch prop to reach optimum operating RPM so was happily sitting on it's curve. It's a bit like Ranmar's post - some combinations just work better than others.

[chris69]

Theres a bit more to it than just adding power, planings hulls work at a angle from stern to bow and it dosen't matter what your deadrise at the stern is, only the designer and his 50k plus cad program can work all those questions out with weights and were is is and beam and draught and how it behaves at what speed.

[NAGG]

Maybe if you were talking in years gone by …… I think in 2020 - there would be very few hulls that could honestly benefit from a lower HP motor .
Lighter / more efficient motors handing off the transom are the way to go

Chris

[Ronje1]

Some pretty knowledgeable stuff there.

I bet that anybody wanting to upgrade (or buy new) would kill for even some of that wisdom.

Put yourself in the shoes of people who don't possess that knowledge.

Where do they start? Phone a friend? Rely on the salesman to be frank and open?

You're talking about them trying to make a decision about a pretty substantial outlay and having to live with the results if they don't get the result that they were looking for.

So, where do they start?

This stuff isn't about about reducing h/p.

Its about a basic starting point to help novices nut things out. There are a myriad of things to take into account and you guys have talked about them.

There are 2 very basic things to think about with motors/boats.

You need something that floats (a hull) and you need something to propel it (a motor).

Get either of those 2 things wrong and you've got a problem that you'll simply have to live with long term.

The hull can come in many different shapes and sizes depending on what waters it's going to be used in. It'll also have weight which will vary again on the proposed uses.

The hull type is the first basic choice facing anybody.

Then the motor.

So THERE are 2 really basic but important and mutually dependent starting variables for people without the knowledge/experience to work it out intuitively.

Perhaps I initially used the term power/weight ratio back to front (I've amended the sheet).

Probably more appropriate was to use weight/power ratio because we're really looking at how many kg each hp has to push around.

Weight/power ratio = (hull +motor weight)/hp. Result is how many kg each hp has to push around.

The lower that ratio the better. Motor doesn't have to work as hard if its not trying to push more kg around.

Looking at the basic hull + motor weights is an ideal starting point. That basic starting point ratio will only go up as you load everything that you need ( increased weight) and THAT varies with the habits/preferences of each individual boatie.

I previously had a 324kg hull/motor combo ( 226kg hull and 98kg x 40hp motor). I thought it performed pretty well when I loaded it up and went fishing. The basic weight/power ratio was 8.2. Each h/p had to push a basic weight of 8.2 kg around. When loaded up I got 3 km/litre.

So I could use THAT as a reference point and as a result I knew that my new vessel had to have a w/p ratio of 8.2 or better (below 8.2 kg/hp) to get at least similar performance.

I looked at quite a few different combinations that looked ok and applied the starting point combinations.

I got w/p results varying from a 9kg/hp to 6.8 kg/hp.

What surprised me was that the one I thought OK (my old one with 8.2kg/hp) was indicating pretty ordinary performance.

I settled on a 413 kg hull combo ( 300kg hull and 113 kg x 60hp) giving a ratio of 6.9 kg/hp. That very basic ratio of 6.9 looked very much like an improvement even though 89kg heavier.

Does it perform better than my old one (the one I thought was OK)?

Yep. Sure does AND I still get 3 km/litre consumption.

Gets out the "hole" really quickly when loaded up with same amount of gear as previously. Old one used to struggle a bit and had to be helped sometimes with weight movements with 3 passengers. Not this one.

The stuff on the LHS of the sheet is the relevant data for this exercise. The stuff on the RHS are useful "add-ons" and mainly cost related. They're incomplete and I wouldn't mind some input on what useful things might be included.

I've nominated Y (for yammie).

To be honest I was looking seriously at the Clark Rebel with the 60 hp but the local Clark guy here was the distributor of Mercury so I was "umming and aahing".

I spoke to the local yammie guy about fitting a Clark Rebel with a Yamaha who said that he had a demo Stessel with a re-plated 60 and other accessories. So I took it after I'd worked out that the w/p ratio was as good as the Clark.

Note also that the approval plate info on the boat will tell you the h/p allowed so THAT anchors one part of the basic w/p equation to what's legal.

I would have bought the Clark Rebel/60hp combo if the Stessel had NOT been re-plated properly. The normal plated Stessel hp for that model is 50 so the resulting kg/p ratio would have been an unacceptable 8.3 kg/hp. Same as my old boat so no improvement.

Any ideas on the sheet for newbies/novice buyers?

Attachment 121443

[Ronje1]

Got it.

Here is the inter-active sheet for some basic things when considering upgrading or buying a new boat. Bit of finger trouble at my end.

It gives a starting point.

Column H is the one to keep an eye on. "Kg/hp ratio"

You can input in the yellow cells. The red cells automatically give the results and you don't have to work anything out.

The sheet is "protected" against accidental input and won't let you put anything in a "protected" cell.

Need to tidy up the right hand side to make it more useful when considering what accessories are needed to bring it up to what you want so looking for useful input there.

You can input whatever motor and boat details that you have looked at to give an idea of things.

The sheet also has a "last updated" window.

You can download and save the sheet to your computer for your own use if you wish.

Attachment 121506

Ignore the bottom attachment (below) in the grey box. Somehow it got uploaded and I don't know how to delete it.

[seastrength]

Got it.

Here is the inter-active sheet for some basic things when considering upgrading or buying a new boat. Bit of finger trouble at my end.

It gives a starting point.

Column H is the one to keep an eye on. "Kg/hp ratio"

You can input in the yellow cells. The red cells automatically give the results and you don't have to work anything out.

The sheet is "protected" against accidental input and won't let you put anything in a "protected" cell.

Need to tidy up the right hand side to make it more useful when considering what accessories are needed to bring it up to what you want so looking for useful input there.

You can input whatever motor and boat details that you have looked at to give an idea of things.

The sheet also has a "last updated" window.

You can download and save the sheet to your computer for your own use if you wish.

Attachment 121506

Ignore the bottom attachment (below) in the grey box. Somehow it got uploaded and I don't know how to delete it.

Thanks Ronje 1

Just out of curiosity, I am wondering how the Polycraft 4.1 Challenger with 50HP Honda stacks up against those other boats. It is a heavy boat but stable platform for fishing. Cheers SS