Do I Need More Power?

[dazk14]

Re: Do I Need More Power?

If Yamaha enduro 85's are readily available, that makes some sense.

Understand though, a single engine will unlikely plane your boat, without an on the spot prop change...which is never fun.

Why don't you look at your current prop and find some numbers. Post back with what you find. Did you buy the motor with the boat... If it was on one of those light fast boats, you may simply be overpropped.

 

[ChautauquaDave]

Re: Do I Need More Power?

I would check the manufacturers plate for maximum horse power and go with it....assuming you have cash to burn! I watch folks on inland lakes with small outboards on pontoon boats and wonder if they are nuts! You lose manueverabilty, head wind power, and lots of hair! Go big!haha

 

[Chris1956]

Re: Do I Need More Power?

Dave has recommended max power. While that is fine, you could get by quite nicely with 3/4 of max power, and still have fine performance. 60% of max power is fine, although performance will suffer a bit. 50% of max power is probably minimum.....

 

[Jungleboat]

Re: Do I Need More Power?

There's lots of things to both respect and love about this forum - and the touching belief in such things as compression figures or manufacturer's plates is simply adorable

It's possible, if it came from Japan or Australia perhaps - but no, there's almost certainly no such plate on this beast.

We're talking Borneo here people, land of the hornbill, head-hunters and horrible options when it comes to buying boats or engines.

Yes Daz, the Johnson was on the boat when I got it. The original prop was slipping so I replaced it with a new SS model of the same pitch etc. Lemme see if I can find the details... Nope, not off-hand. I suspect it probably is a little bit over-propped, just a bit. I think it certainly was, before I sealed off the live baitwells and made the thing substantially lighter...

Ideally, if I can, I'd like to leave that Johnson on there and sell the boat as a complete and running vessel, rather than pulling that engine off. It's a great engine in that it's still going after 30 years, which I have to tip my hat too. On the other hand it's a 30 year old gas-guzzling monster that never tires of finding new ways to short-out the electrics so it can give one of the cylinders a rest. I affectionately refer to it as my Johnson V3...

If I were to sell it to a local without an engine they'd either stick a Yam 40 on there and be very disappointed, or they'd have to budget for a 85 or more anyway. May as well sell it with the 90 already on there, as while I respect that engine, enjoy it's throaty burbbly sound and have a degree of affection for the old thing, I'd like to get rid of it.

You say a 115 would push it OK, do you mean on plane?

Yamaha 115s are also fairly common, though a lot more expensive.

If I had 2 of those that gives me 230 or so with both, which should be plenty, and possibly on plane with just the one? If so that would be the perfect set-up, albeit pricey.

In fact if it could plane on one then I'd only use one for most of the time, only using 2 engines if really needed to climb up some big swells or something. As I said, I'm not a speed freak, I just wanna go further out for the fishing


JB

 

[Chris1956]

Re: Do I Need More Power?

JB, Boats with twin motors rarely can plane with a single engine running. They are too heavy for that. Any idea of the weight of that 23 footer? Maybe a single 115HP motor is all you need, for low performance.

 

[Jungleboat]

Re: Do I Need More Power?

Hi Chris, nope, no idea of the weight.

For the 'refit' I'll be keeping the weight down, no fancy luxury chairs or anything, certainly no live baitwell...

My impression is the 200hp boat in that advert is somewhat underpowered, that my current 19ft boat is under-performing for a 90hp and that the 130hp 4-stroke engine, IF it is running properly, should give me the same kind of performance I'm currently getting anyway.

If that's the case then I'll probably just go for the 130. That's especially true if it has a working tachometer with it, because then I can experiment with prop pitch.

If pitched so she's capable of red-lining on the flat, then she should have the grunt to ride over swells, right?

The previous owner of this boat says with 150 it could "only" do about 20 knots. Bearing in mind what I said earlier about needing 4X the power to go 2X the speed, I don't think there's any real difference between 150 and 130. If 150 will plane the thing and push it around at 20 knots then so should 130, near enough.

20 knots is fast enough for me.

Put it this way, to hit 40 knots it would, in theory, need 4x the 150, ie 600 horsepower. That's 4X the engine weight, 4X the fuel consumption and 4X the chance of smashing the hull if I hit one of the many floating logs around here...

20 knots is fine, presuming that engine is economic to repair. The other option is if I feel it IS under-powered and the boat needs more, well I can just use it in the bay and on the river like I am my current boat anyway, while saving up for a bigger powerplant.

Ah. All makes sense, right?

Then I look at these 2 photos...

View attachment 122951View attachment 122952

The 23 footer is MASSIVE compared to my current boat!

Some of it is a trick of the camera lens, the 19ft photo was taken with a 24mm extra-wide angle, whereas the out-of-focus shot of the 23 footer was with a 40mm lens.

Even so, looks like a huge difference?

*scratches head*


Oh buggery...
JB

 

[Jungleboat]

Re: Do I Need More Power?

OK, an update

In the end I found an old Evinrude 200 V6 circa 1993. Didn't cost too much but spent as much again having it fully reconditioned, new liners, everything. Also found a 15 HP Yamaha, which I fitted to starboard with a raisable mounting bracket thingy.

With 4 people on board, half a tank of fuel, the Yamaha attached but raised and just using the prop that was already one the engine, here's what happens:

Idle speed - Boat chugs along OK, with good steerage.

Quarter throttle - heavy vibration (not good but not sure why?) not noticably faster than idle really. A bit faster.

Half throttle - vibration dies away, feeling of the boat gathering speed then you distinctly feel it coming up onto plane

3/4 throttle - Hold on tight! Up on plane in about 3 seconds, everyone in the boat falls over...

WOT - about the same as 3/4 but more noise, going on to a higher top speed.

So what is the top speed? Again with 4 people on board my GPS showed a top speed of 35 knots or 40 mph or 65 k/ph, whichever you prefer. That's over fairly choppy water and faster than I'd normally go over a surface that rough.

I'd say this is more than enough power, especially as my father in law may be at the wheel at times...

She goes fast enough that I slow down for turning, something I didn't really need to do with my old boat. With my old boat you could give her full throttle and full steering and she'd just lean over like a motorbike. With this boat you can feel her starting to skip sideways; I can imagine her throwing you out the boat if she hit an errant wave or wake.

Judging by the howling wail behind me I think she might be a little bit under-propped, as she can really scream at WOT, yet she does seem a bit hesitant at lower revs?

Still don't know how she performs with the little 15 HP aux' motor I've added, as for some reason it wouldn't start on the day. Have cleaned the carb and she starts OK off the boat, so hopefully she'll start OK next time she's on it.

I'll be replacing the transom before doing any further testing but just thought peeps might want the update



JB

 

[Zookdesign]

Re: Do I Need More Power?

This has to be one of the funniest reads i've has in a long time.. JB you sure know how to write a story..