Outboard size for a 4.75 tinny ???

[seb7701]

Hi all.
Need a little help please - I am current shopping for a replacement Centre Console tinny and have found a bunch of good ones in the 4.75 range, however they all seem to have 50's strapped to the back end!!!
I previously had a 4.1 with 40 and a 4.95 with 70, both of which were ideal, but can anyone tell mean the real world version of whether a 50 would push one of these thing sufficiently with a few people on board??

Any help would be appreciated.

Cheers,
Seb

[scottar]

Depends on the size of the people, the individual hull, the motor itself and what you are expecting in a level of performance. In two stroke, I would think 50 or 60 would be about right. 4 stroke I would be looking at 60 - 70.

[seb7701]

Thanks mate - yep, bit of a hard one as I would be think bigger would be needed, but I get the impression that I could be surprised. They are 2 strokes that I'm looking at and at most, I would be taking 3 average adults and 2 x kids.

[scottar]

Mate of mine was running a Brooker 5 metre with a 50 2 stroke. Would still plane with him, the missus, 3 kids and a boat full of crab pots. I ran a 4.5 with a 40 on it for a lot of years. It would plane with 4 adults. You can always use more horsepower on the flat days though ;D

[seb7701]

Yep, good examples. I am thinking it might do the trick - maybe good excuse for a 4str upgrade later...
Just thinking that I whilst I might have enjoyed the 70 on my last boat, I never really used the power that was there anyway and any bar crossing would be a rarity...

[Andy56]

My first boat was a quintrex 4.8m runabout with. 60 4s yamaha. It did everything requested of it. However, you soon learn that a bit more oomph is welcomed.
personally, if you cant hit 70km/hr you need more power. Same as my signature, 130 was more than enough but i wanted more. 150 was on the cards until divorce killed that one. Yes, what they say is true, get the biggest you can aford.

[seb7701]

Thank Andy - yep, big fan of max power, just as when I went from 2cyl 30 to a 3cyl 40 once - world of difference then even. Always a bugger finding nice, but slightly under-gunned boats for sale!

[up the creek]

50 may do it but after the weight your talkin youd be punchin it to get up where a 70 would do it more comfy and not need to rev as hard i dunno but 50 is safe just but if the hull can handle 70 that be the minimum id put on it with all the gear etc.. agree with scottar 50 or 60 would do it but id rather have extra hp if needed and not use it then not have it...

[Marlin_Mike]

trouble is, when they advertise boat packages, they tend to price them with the smaller lower end HP motor rather than the upper end of the Outboards HP, as marled on the plate. this keeps the price down and makes the package look very good value, Sadly, this can sometimes end up with boats being underpowered.

[bluefin59]

I have a 60 2 stroke on my 4.5 mt side console and most run 50 hp I certainly believe in going to the hulls max as far as HP goes mate ,otherwise you will always be kicking yourself ...Matt

[Moonlighter]

When i was buying my current boat, i was debating the same issue, and had a conversation with my local outboard dealer. It went like this:

me: i am thinking a 90 would be OK.
him: what is the hull's max rated hp?
me: 115
him: i have never had a customer come back to me and complain about too much hp on their boat. But i have had plenty who said they wished they had gone max hp. You know what you should do.....
me: then 115 it will be.

As he predicted, I have never thought "gee i wish I didnt have that much hp" and on a many occasions, I have thought "heck, i am glad Ive got that power on the back, any less could have been a worry!"

Go with the max rated hp for the hull, or very close to it. You will then not have any regrets later.

[seb7701]

Thanks Gents - you're all spot on - you never complain of excess power!! I'll have to think about this one as either a re-power waiting to happen or give it a swerve....The scary part is the number 4.75's and the like which I've seen with 40's!!!

[NAGG]

I've just re powered a 5m seajay barramasta ..... Originally with a 70hp Yammi it was ok -- 2 blokes on board

Add more gear & big battery for the leccy , a live bait tank full of water and it became a sluggish boat ..... getting out of the hole quickly was the issue . Now with a 100 yammi on the back it feels like a different boat that runs at the same speed as the WOT (70hp) but now at only 4000 rpm & burning half the fuel .

The old she will be right & X is plenty ..... is not the best approach - You really should be choosing a motor that is at or close to the maximum rating.

Chris

[Noelm]

Correct, lots of salesmen will advise on a motor that makes the package cheaper, and more attractive, and sell a motor that is just OK, but there is a world of difference between OK and right! A well powered boat is a delight to operate, you don't always need max rec HP, but up towards max is always better.

[PixieAU]

I think the boat and type of fishing you do is important. For example, my hull is rated to 115 but I installed a Suzi 90 4 str.

Partly because the next size up went to a bigger block and the price leapt considerably. At the time I couldn't justify the additional dollars for the extra HP.

But it's only on glass out or in a river that I push it to WOT otherwise, in the bay where I go most, the hull is often only comfortable at 3/4 throttle (~4500 rpm).

So what I'm saying is that whilst the hull will handle more HP I'd rarely be able to use it due to the limitations of the hull. Instead I enjoy the better fuel economy all the time and just occasionally wish I had more. Plus the dollars I saved make the first few years worth of fuel free!

By the way, it'll top out at ~55km/h which is usually fast enough for me and hole shot is fantastic.

[scottar]

I think the boat and type of fishing you do is important. For example, my hull is rated to 115 but I installed a Suzi 90 4 str.

Partly because the next size up went to a bigger block and the price leapt considerably. At the time I couldn't justify the additional dollars for the extra HP.

But it's only on glass out or in a river that I push it to WOT otherwise, in the bay where I go most, the hull is often only comfortable at 3/4 throttle (~4500 rpm).

So what I'm saying is that whilst the hull will handle more HP I'd rarely be able to use it due to the limitations of the hull. Instead I enjoy the better fuel economy all the time and just occasionally wish I had more. Plus the dollars I saved make the first few years worth of fuel free!

By the way, it'll top out at ~55km/h which is usually fast enough for me and hole shot is fantastic.



This does raise a point of interest with the "always fit maximum horsepower" train of thought. In principle, I agree but you need to ensure that by going to maximum horsepower in your chosen brand of power plant that you will not be introducing handling traits that will be annoying for most of the boats usage simply to gain that bit extra zing that will only be used on those all too rare occasions when conditions allow. I have seen this first hand with my own boat where the difference in engine weight produced a rig that has needed a considerable amount of tweaking to get it to perform as I wanted it when things weren't so nice (seems to be most of the time these days) . If the extra horsepower comes without weight penalty - not an issue as a general rule (it may use a bit more fuel though) but if the maximum horsepower brings about significant weight penalties, the grass is not always greener.

[NAGG]

This does raise a point of interest with the "always fit maximum horsepower" train of thought. In principle, I agree but you need to ensure that by going to maximum horsepower in your chosen brand of power plant that you will not be introducing handling traits that will be annoying for most of the boats usage simply to gain that bit extra zing that will only be used on those all too rare occasions when conditions allow. I have seen this first hand with my own boat where the difference in engine weight produced a rig that has needed a considerable amount of tweaking to get it to perform as I wanted it when things weren't so nice (seems to be most of the time these days) . If the extra horsepower comes without weight penalty - not an issue as a general rule (it may use a bit more fuel though) but if the maximum horsepower brings about significant weight penalties, the grass is not always greener.

& that is a fair point ........ take my scenario the F70 comes in at 119kgs (996CC) . If you step up to the F80 (1596CC) - you add 49kgs & gain a modest 14%ish more power ....... but the F100 comes in with the same additional 49kgs but gains around 43% more power . so if you were looking at Yamaha .... you would either stay down at the 70 ( working it harder) or you go the 100hp .

Sometimes though you might find that another motor brand may be the best option ........ eg a Suzuki 90 comes in at 15kgs less than the F80 yammi but gains in power .

Chris

[fishwpa]

This does raise a point of interest with the "always fit maximum horsepower" train of thought. In principle, I agree but you need to ensure that by going to maximum horsepower in your chosen brand of power plant that you will not be introducing handling traits that will be annoying for most of the boats usage simply to gain that bit extra zing that will only be used on those all too rare occasions when conditions allow. I have seen this first hand with my own boat where the difference in engine weight produced a rig that has needed a considerable amount of tweaking to get it to perform as I wanted it when things weren't so nice (seems to be most of the time these days) . If the extra horsepower comes without weight penalty - not an issue as a general rule (it may use a bit more fuel though) but if the maximum horsepower brings about significant weight penalties, the grass is not always greener.

Got me thinking about going the Suz DF175 on my BC 670c over the Min 150 & Max 200. Hoping the 175 will be the right choice - power to weight. I had a surtees 4.85 cc with a merc 4s 60hp on the back, max was 70hp I think and the Yam 70 from what I can remember researching has basically the same output as Merc 60 (not 100% on that). The Merc had no where near enough ponies out of the hole with 2 blokes on board it was dangerous but was basically the largest HP there was keeping it within weight limit. Wondering whether the 200 is the way to go.

[up the creek]

if a suzuki 175 cant do it.. can a 200?? im sure a 175hp will be plenty on that size boat but like scottar said whats more important the weight or extra hp

[Moonlighter]

175 and 200 4cyl Suzuki weigh the same. Easy choice, go the 200!

[gofishin]

It's funny how that, 'today', if an offshore boat doesn't do 40kn (or near to it), it is considered by many to be underpowered - yet our fathers, and possibly their fathers too, used to repeatedly and safely fish the same areas we fish... in boats with less HP, which were much slower and many with less reliable and less user-friendly 2 stroke O/B motors than our O/B's of today - regardless of their stroke cycle.

What's more, there was no such thing as a GPS or a Plotter. The 'all natural' coastal bars had no groins or nice big rock walls, and were a lot more treacherous. Sounders worked on paper or displayed depths by small flashing lights on a circular dial (anyone remember these??).

AND... there was no internet, live weather, wave and swell feeds, and the weather man's predictions were far from the 'highly accurate' (????!!) predictions we get today!

How did they/we survive all those trips??... and ... did our mothers really let us go out with dad 'in those slow dangerous boats' in those situations???

Ok, semi-rant ... with a touch of sarcasm ... is over [emoji1].

Yes, like many, my boat does 40kn. But do we really need it??? NO, don't think so!


This does raise a point of interest with the "always fit maximum horsepower" train of thought. In principle, I agree but you need to ensure that by going to maximum horsepower in your chosen brand of power plant that you will not be introducing handling traits that will be annoying for most of the boats usage simply to gain that bit extra zing that will only be used on those all too rare occasions when conditions allow....Some wise words in your post Scotty, and I particularly like this ^^^ bit.

Other than considering any weight penalty very seriously, there is also another factor that I believe is very important, and always like to consider very seriously. This is... the 'consequence' of too much power (and hence prop pitch), and the resulting extra speed at the 'all too critical' lower engine revs/lower planing speeds.

To explain, we need to delve in to a bit of math and physics... easy to do... but who really wants to do/read/get their head around this stuff on a Sunday night??? [emoji1]


... but if the maximum horsepower brings about significant weight penalties, the grass is not always greener.Yep, agree 100% Scotty. I would even say it is "rarely greener" [emoji1].
Cheers
Brendon