Re-Powering Zip Utility

Outboard designs up to 14'

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Zipit
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Re-Powering Zip Utility

Postby Zipit » Sun Feb 14, 2016 8:17 am

Good Day,

I have a 1969 Zip Utility. At least that is what we believe it to be. It has been powered by a 1983 25hp Mercury and I am looking at swapping that for a 1966 Mercury 50hp that sits on my 1960 J.H.Ross Cedar Strip that I am selling. Both motors are in excellent condition.

Should I be reinforcing the transom? Suggestions?

Thanks.
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vupilot
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Re: Re-Powering Zip Utility

Postby vupilot » Sun Feb 14, 2016 8:36 am

That's a couple of nice looking boats! Where are you located?

You would be at the limit of what it was intended to take weight and power wise. In my opinion its a little much but others have done it so we know it can be done but I think the motorwell adds some strength to the whole setup and since your utility layout doesn't have that I would think about adding some extra knee braces. Similar to the one that should attach from your keel to your transom I would consider adding some in the upper corners of the transom to the sheer and maybe some from the floor battens up against the transom.

How does it perform with the 25? How much weight can you have in the boat and still get on plane and cruise nicely with that? Your Zip looks lighter than most with the utility layout and basic seats. I would think that would be a nice match with the 25?

Zipit
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Re: Re-Powering Zip Utility

Postby Zipit » Sun Feb 14, 2016 8:47 am

We are in Ontario.

I think the 50 is too much for the Ross. I have just put in 38 new ribs and a new transom. It is really better suited to the 25 I think. Best I can figure they were rated for a 35 back in the day. It is a 14' boat too.

The Zip does about 20 knots with the 25 Merc on it. We took her on a 500 mile camping trip up the Trent Severn and would estimate we had about 600 lbs including us on board. Performed well.

The boat feels a bit underpowered with the 25. It feels like it wants to go faster. Or maybe that's me. 8)

cusoak
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Re: Re-Powering Zip Utility

Postby cusoak » Sun Feb 14, 2016 9:19 am

No they do want to go fast.
I have a 1961 Merc 45 hp short shaft on mine.
It is 44 cid
Back then the only diffrence between a 45 hp and a 50 was the carbs.
How thick is the transom on your boat now and does it have a knee brace between the keel and transom.
Jeff

Zipit
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Re: Re-Powering Zip Utility

Postby Zipit » Sun Feb 14, 2016 10:22 am

The transom is 1.5 " and the knee is solid. See attached.
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Cabron
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Re: Re-Powering Zip Utility

Postby Cabron » Sun Feb 14, 2016 4:56 pm

I have that same merc on my Zip. It`s a nice light motor and gives me 26mph. Plenty fast for me
but it sure is a noisy thing. Does yours make a big racket too? I don`t know much about outboards and never expected it to be so loud and annoying.
I may get a four stroke if It gives me a more pleasant riding experience, but I really don`t know how much of
a difference there is between 2 and 4 strokes in sound quality. Can anyone recommend a quiet 4 stroke? Thanks

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Re: Re-Powering Zip Utility

Postby joshuab » Sun Feb 14, 2016 8:15 pm

Cabron wrote: Can anyone recommend a quiet 4 stroke? Thanks



Yamaha and honda in that order, the new yamahas are dang near silent, find one at a local marina and have a listen, you will be impressed.
I cut twice and it's still too short :mrgreen:

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galamb
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Re: Re-Powering Zip Utility

Postby galamb » Mon Feb 15, 2016 6:56 pm

Zipit - I'm going to throw out some numbers here and will try to tie it all together without getting you (or me) totally confused.

Your 25, being the year that it is is making 25 "shaft horse power", so 25 horses at the prop if you like.

The earlier 50 horse model was measured in Brake Horse Power (base of the crank shaft), so basically 40 horses at the prop.

Basic rule of thumb with outboards: a 50% increase in horsepower translates into a 15% performance increase, in terms of top end speed on most planing hulls.

Given that if you are making 20 knots with the 25 horse, you could expect to make somewhere in the 24 to 26 knot range with the (BHP) 50 - all else being equal.

The "weight" of the motor has little to do with whether the boat can handle it or not. The weight is suspended on the transom and while it may cause some balance issues if the replacement motor is somewhat heavier than the existing motor, the transom "will" hold it. It is the "stress" imparted by the motor on the transom that may become the issue.

1 horsepower produces about 26 to 27 lbs of "thrust" (it's not a direct equation, but close enough). So if your 25 horse is perfectly tuned and putting out max horsepower (never does, but for the sake of argument) it would be putting 25 (horses) X 27 lbs (thrust) = 675 lbs of "stress" on the transom which is translated into "forward motion" since the transom doesn't yield (or not very much).

(so if the transom is easily handling the 675 lbs being imparted by the thrust of the motor, in theory you could hang a 500 pound 300 horse 4 stroke on the back and the transom would "hold it" - you would probably swamp the boat, but as long as you didn't fire it up, the transom would "take it" without failing)

Because the propeller is at the bottom, under the boat, when in operation it's trying to "crawl under the boat" - the opposite reaction to that is that the torque created by that is being transferred into the motor bracket (top of the transom) so that the "lever action" of that is trying to "rip the top of the transom" from the boat - if it doesn't yield it results in "forward motion".

This pic will better illustrate what I'm getting at:

Image

So if you move up to a 50 BHP (40 SHP) motor and sort out any balance issues you need to strengthen the transom so that it will hand the new thrust/torque that will be applied to it. It will produce 40 (SHP) X 27 lbs (thrust) = 1080 pounds of thrust or about 400 more pounds of thrust than the 25 horse applied. Doubling or Tripling the "knee" and perhaps adding some bulk to inside (top) of the transom cut-out (2X6 across the cut-out for the motor) would probably be far more than you would need from a safety point.

I hope I have been clear enough that I didn't lose you :)
Graham

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Re: Re-Powering Zip Utility

Postby Zipit » Mon Feb 15, 2016 8:05 pm

Graham,

Thanks for the detailed reply. Lots to consider. Great explanation.

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Re: Re-Powering Zip Utility

Postby cusoak » Tue Feb 16, 2016 6:55 am

I am reading a book called Iron Fist it is written by Jeffrey I Rodgenged. It is about the Life of Carl Kiekhaefer.
What it says in the book about Mercury motors is that they all made more HP than rated HP.
Their motors also weight less than other motors of the same horse power, allowing for greater speed.

My 1961 Merc 400E 44 CID motor will push my Zip with just me in it on smooth water with a 2 blade brass prop 28 MPH
All that being said you can play with different props to better speeds at lower RPMs.
As far as the noise thing they are very.
I have a Merc. Friend that has helped me with my motor and has told me about a sound deadening material that you use in place of what came with the motors that is supposed to make a difference in how loud they are.
Not sure what it is now but will wind out and let you know.
Jeff

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galamb
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Re: Re-Powering Zip Utility

Postby galamb » Tue Feb 16, 2016 7:53 am

Yes, it is true that Merc tended to "under-rate" their horsepower by sometimes as much as 10%.

Although they are a predominant North American outboard "today", back in the late 1950's through the 1960's OMC was king and accounted for most of the innovations and "new records" in the outboard world. So in order to try and gain a little edge, Merc built say a 44 horse motor and called it a 40. In fact, before Kiekhaefer merged with Brunswick they were selling less outboards than a couple names that no longer exist (McCulloch, Atwater etc). Merc was just another small family run (pretty much one guy) company trying to scratch out some of the market share.

Now with the EPA and the European emission control standards in place most outboards produced in the last 20 years are pretty much tuned to the max and they can not, by regulation, produce more horsepower than their emissions sticker says they produce (at least from factory) - further to that, since some time in the late 1990's (memory is getting foggy now) the following has existed, at least in the US:

"EPA regulations prohibit changes to engines that could affect emissions limits. Per the service manual, "The dealer and/or consumer is not to modify the engine in any manner that would alter the horsepower or allow emission levels to exceed their predetermined factory specifications." The only changes permitted are carburetor jet and gearcase/gear ratio changes for high altitude operation as detailed in applicable Mercury Marine Service Manuals."

This more than anything else led to the push towards 4 stroke and Direct Injected 2 stroke outboards, both of which produced less emissions per horse.

Merc hung on as long as they could, and in fact a number of 2 stroke models remained in production until 2012 but were sold outside of the US (sales of which pretty much wrapped up in 2005 in the Domestic US market) - being in Canada I still could have bought a "brand new" 9.9, 15, 50 or 90 horse model 2 stroke until 2012.

There was a number of myth's created about the 4 strokes in order to meet the new marketing reality. They (the Mfgs) had to convince the public that they were a superior product compared to "grampa's 2 stroke" and they did so with selective facts.

Yes, they do burn cleaner than a carb model 2 stroke, also cleaner than a fuel injected 2 stroke - no doubt about it. But they have infinitely more moving parts, they are far more sensitive to "lack of maintenance" - the service schedule became the "minimum you had to do" instead of a "guideline" of what would be prudent to do.

The first great myth was that they are "far more fuel efficient". If you parse that out then it's "partially" true. If a given outboard never exceeds 3500 rpms (on average) a 4 stroke will burn considerably less fuel than a 2 stroke. But, at full throttle a 90 horse 4 stroke burns every bit as much gas as it's older 2 stroke counter part - and we have to be honest. The average boater has a "two speed motor" - they idle out of the dock and through the no wake zone and then hammer the throttle. So at least most 21' and under pleasure craft owners don't reap the "fuel saving benefits" that were the hilight of the glossy ads.

In head to head power comparisons whether you look at torque or top speed per horse, the 2 stroke always wins, every stroke is a "power stroke". Two strokes also have a way better hole shot, the motors are almost always significantly lighter on a horse per horse basis (although the 4 strokes are getting lighter) - and pushing "extra weight" is always more costly all else being equal.

Then there is the "they are far more quiet" - again, yes and no. Again, at lower rpms you can barely hear them running. At full throttle if you measure the dB's produced they are just as loud or in some cases "louder" than a comparably horsed 2 stroke model but the sound is "different" - it just seems a little more "tolerable" to the ear despite being as loud or louder. But there is some (romance) for us older folks when we hear the "whine" of a 2 stroke wound right up :)

You can fiddle with a 2 stroke to "tone them down" a bit. They use water as a muffler. The exhaust is (vented/ported) into the "leg" which is full of water during normal operation. The shape, style, diameter of the exhaust tube that is submerged in that water has a great deal to do with "how it sounds" - what you need to be careful of is "restricting" the escape of the exhaust gasses. Yes, that would quiet it down but it would also reduce your horsepower. If you compare say a 75 and 90 horse outboard they are about 98% "mechanically identical". The ability to make the extra 15 horse is totally dependent on the 90 horse being able to "breathe in and out" more efficiently (at a higher volume) than the 75 horse - so if you mess with that ability you can either 1) increase horses but make it louder or 2) decrease horses but make it quieter. To no real avail most of the mfg's tried various configurations (horn shaped cones etc) to try and make them "more quiet" - all they really did was complicate the tear down process for guys like me who work on them, adding extra parts, gaskets and seals which take both time and money to replace and provide a near zero "net benefit" :)
Graham

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A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

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Andy Garrett
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Re: Re-Powering Zip Utility

Postby Andy Garrett » Wed Feb 17, 2016 11:22 am

I have the 50 Merc on my Zip.
I also have the thinnest (1.5") transom, but I have a well tied-in motorwell.
The motor weights about 175lbs.

If it were me (and I almost did this when I built mine), I would add knees to the transom-sheer junction at least.

That said, mine has never worried me, even after a 40-mile tow when I forgot to install the transom-saver!
Andy Garrett

Perhaps the slowest Zip build in Glen-L history...

gdcarpenter
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Re: Re-Powering Zip Utility

Postby gdcarpenter » Wed Feb 17, 2016 3:45 pm

Just to complicate things. When is the torque on the transom the greatest? I once tried to follow a very good discussion on this, by mostly engineers, no concensus was reached that I could fathom.

I would think the initial takeoff would be the worst load, even though the engine is not putting out max. HP at this point. Seems the 'inertia' of the boat vs the thrust of the engine would be maxed when you 'drop the hammer'.

As I understand it, in the days of yore, when ships were built out of wood and men were built out of steel, they kept building lighter and lighter cathedrals with thinner and thinner flying buttresses until one collapsed, then they knew what the 'Maximum' was.
This is my first, last and only boat build.

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galamb
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Re: Re-Powering Zip Utility

Postby galamb » Wed Feb 17, 2016 5:01 pm

I "don't know for sure" but would tend to agree that the greatest stress on the transom would occur during the "hole shot" particularly if the throttle was applied quickly.

The reason why I would think this would be the case is because you have 1) a body at rest (the boat) 2) more of the hull is in contact with the water than at any other time in the sequence of motion (once underway a planing hull will start to rise leaving less hull in contact with the water therefore; 3) the resistance to motion is greatest and 4) friction is at it's highest point.

If I back track a touch to my explanation above, this is where "thrust" also plays into the equation and not "horsepower".

Horsepower is measured by "distance traveled over a measured length of time" where thrust is simply pounds of force applied in one direction. If that sounds convoluted you can simply consider a commercial jet sitting on the runway getting ready to take off. With the brakes applied they throttle up the engines so they will have enough power to lift all that weight off the ground before they run out of runway.

So what "horsepower" are those engines producing? The answer, at least while the brakes are applied is ZERO horsepower because there is no "distance traveled" - yes, tons of stress on the wings being transferred into the super structure but totally "unrelated" to horsepower.

(back on track here).

So you have say a boat, motor, junk and people displacing 800 pounds sitting perfectly still on the water. You hammer the throttle to "take off". The motor winds up to near max torque (not horsepower) and produces 1000 lbs of thrust. That thousand pounds of "thrust" is applied against the transom of an 800 pound object that is meeting the resistance of 800 pounds of water (that is being displaced by the sitting boat) which while "slippery" is still trying to hold the boat back.

Once the boat gets on plane some of that 800 lbs of boat is mitigated by the "lift", less of the hull is "dragging" on the water (it's no longer displacing the entire 800 pounds) so there is less resistance borne by the transom to the 1000 lbs of thrust being placed on it by the motor.

Now, I'm just a part time outboard mechanic/power boat rigger who isn't all that great at math, and certainly not an engineer, but that is what "I think" is happening.
Graham

Yes, Plywood is "real" wood :)

A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

cusoak
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Re: Re-Powering Zip Utility

Postby cusoak » Fri Feb 19, 2016 6:33 am

In the next couple of days I will be picking up the material my friend says will quiet down our old Merc,s.
Will let you all know what it is, along with a picture. It will replace the piece that is inside the cover.
By the way Mercery back in the day did an test to that there new merc, 6 cylinder dock buster way reilable. It was run at there secriet lake in Flordia.
They set up a course and made enough laps to simulate 25000 miles ,with fueling and driver change made on the fly.
Jeff


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