Modified 102

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Collector Inspector
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Re: Modified 102

Post by Collector Inspector » Mon Jan 15, 2018 8:00 am

Jon

If you play reeds on the block you are the victim of the induction timing.

If you play reeds directly on the crankcase you have room to move with transfer timing.

I am also a bit confused ................

Keep us posted aye.

BnC
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Oyster 49
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Re: Modified 102

Post by Oyster 49 » Mon Jan 15, 2018 7:46 pm

Some outboards in the 50s had a poppet valve similar to a reed valve which opened and closed by crankcase pressure. I always thought it was a good idea. Don’t know if it is a performance gain though?

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Re: Modified 102

Post by headdownarseup » Mon Jan 15, 2018 9:39 pm

Shall i try to explain things a bit simpler here before we tie ourselves in knots again.

I haven't built anything yet.
Yes, wherever possible i would like to build a 102 that to all intents and purposes looks like any other 102 as far as possible.
Yes, i'd like to keep the 102 gearbox, with whatever prop seems to work to give the best option for going fast (however fast that will end up being we will have to see) But if it transpires i can easily be convinced to choose another route with some of this. I'm not that fussed really, as long as what is above water is instantly recognised as a 102.

This is ENTIRELY a thread about talking over the theory side of things before anything gets built.

I would like some clearer explanations into why some boat designs go faster than others for a given power range, instead of guys saying yeah Jon , just use this design and you'll be right. I want to know why i can't use a different design. I want to know more about why props lose grip, i want to know about what needs modifying on props and how to do it. I'd like some numbers i can actually work with instead of mumbojumbo that nobody understands. Pictures, diagrams etc. etc. something i can read for myself that might help somebody else with the same problems but were afraid to ask.

I'd like ACTUAL proof rather than hearsay of what some of the stock parts are REALLY capable of and just how far we can stretch things. If that means testing to destruction to dispel maybe a few myths then great! That way we can all say that THAT is the point to back off before it all goes horribly wrong. I, like many others, would like to know what could be achieved on a small budget without going down the route of expensive machining . I don't own a lathe or a pillar drill or anything fancy like that, i just have my hand tools and a bit of know how. I reckon there are an awful lot of seagull enthusiasts like me with limited tools and space for a project like this, but were too afraid to ask for fear of getting laughed at by you lot.

Homebuilds are of course more than welcome, and with some actual working numbers and notes we might start to make some headway with this topic.
We've all read different books that say one thing or another. We've all read that certain things must be adhered to in the pursuit of power.
Great, me too, but a lot of what i've read before has some sort of bearing with either motorcycles or cart racing which have a very different set of parameters in which they work. Nothing about old outboard engines though unsurprisingly.
The dear old 102 seagull was designed from a time when most of what we've read in books was still in it's infancy, and although i trust the seagull engineers have done a pretty good job with their outboard engines i still can't stop thinking "what if" with a lot of it.

Bottom line is......how fast is fast? Is it fast enough for you? Will it be fast enough for me? Could i go faster than you and everybody else??

Now of course if a 170 or 5R just happened to drop into my lap, all of what we're discussing here won't mean a damn thing anyway, BUT that would be cheating. I've always had a huge soft spot for the 102 and this alone should be good enough for a talk on making it go a bit better.
How much better only time will tell.
That's what makes this such a personal thing too. More experienced gull fiddlers will have been through a lot just to get where they are now. Great. But what about some of the newbies coming into this hobby of ours without the first idea of what goes where! This is as much for them as it is for us, so don't be shy gents, let's hear what you've got to say on this


Let's talk about some stuff!


Jon

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NaughtyBits
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Re: Modified 102

Post by NaughtyBits » Mon Jan 15, 2018 10:25 pm

No offense - but sounds like you want a lot from others who've had to put a lot of time reading, learning, listening & building, themselves.

Some people have good advice about props because they actually go do the work & test what they learn for themselves. Some people have good advice about boat designs because they do the same, etc., etc., etc.

What kind of proof are you expecting others to give you exactly, to 'justify' their advice to you, if you're only interested in discussing 'theories'..? I don't think that's quite how it works...

There have been quite a few threads on this site about prop work, as just one example. If it was me - I'd give those a read, then actually go work on a few props & test that advice out. If I found something didn't work for me - then I'd come back with more questions seeking advice as to why. I wouldn't be demanding proof of anything before I'd even spent the time taking a file/dremel/disc grinder/chainsaw/chipping hammer, etc., to a prop to see for myself.

Generally, I imagine you'll have a much more productive time getting advice & information about mods that interest you, if you have specific questions. If those questions come from some kind of experience (failure, success, partial success, etc) - then the advice & help you get is only going to be that much more meaningful and easier for you to understand & accept.

Just a suggestion - don't ask me to prove that theory. :lol:

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Re: Modified 102

Post by NaughtyBits » Mon Jan 15, 2018 10:47 pm

Example: “Guys, for my project, I’m thinking of using a 102 leg & 4 blade hydrofan to get more rpm at wot. What do you think?”

The first question you’ll likely get in an answer is “What are you using now? What rpm’s are you seeing at wot now? Etc.,..”

How do you see yourself being able to answer, in ‘theory’?

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Hugz
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Re: Modified 102

Post by Hugz » Tue Jan 16, 2018 2:32 am

Just for us non racing folk. WOT means wide open throttle. Took me a while to work it out. I think I'm most used to the term "pedal to the metal" but that is not relevant.

Good to see the reality checks......

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Re: Modified 102

Post by NaughtyBits » Tue Jan 16, 2018 4:08 am

Doh, sorry - yes WOT - Wide Open Throttle. As opposed to FTWS - F•••••• Thing Won't Start...

Jon - sounds like you have a fair 102 collection. A good start might be to identify which is your fastest, all things being fairly equal (good rings, gaskets, same fuel ratio, etc.). Then identify the best example of each different cylinder casting you have (as little wear as possible, etc.). Take each example & test, swapping out cylinders on the same motor on the same boat (obviously not a barge!) at the same transom height. Record speed & max RPM's for each cylinder (ideally same day, same conditions). Now you'll have a set of numbers for each cylinder variant (6 or 7, maybe more?) and you'll know which cylinder is your fastest.

Then on the bench (again, same motor), swap out and port map each cylinder variant, recording durations, primary compression, etc. Now you'll have numbers that you can compare to begin to explain the 'why' behind the differences recorded in speed & max rpm's for each cylinder variant. That info will also help readers offer meaningful advice for you to modify whichever turns out to be your fastest cylinder (as tested), if that's what you want to do.

Of course, this won't take into account the pretty large variety in machining differences across each cylinder casting - but you have to start somewhere... It's a lot of work... fun work, though.

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Re: Modified 102

Post by Collector Inspector » Tue Jan 16, 2018 9:38 am

Just watching from now on.

BnC
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Re: Modified 102

Post by NaughtyBits » Tue Jan 16, 2018 12:53 pm

Same for now.

And please don’t read as having a go at you Jon. Based on all the good advice I’ve received & tried over the years - that’s where I genuinely think you should start with your 102 project.

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Re: Modified 102

Post by headdownarseup » Tue Jan 16, 2018 10:08 pm

All good points, and duly noted :P No feelings have been hurt this i end, you're alright :lol:

I've done a bit of what you've suggested already Jason. The only fly in the ointment is my big heavy "barge" as you call it :shock: (hence my interest in building a smaller and lighter boat that could do this project some justice :P ) Pointless testing this out on my heavy canal cruiser isn't it, although i have noticed a subtle difference with a couple of my older 102's where i cleaned up the prop.
I'm looking towards Nudge for some guidance here.

Rather than looking at one of my more cherished 102's as an example for improving,(13 and still breeding :roll: ) i have a collection of bits (quite a lot of bits) that once assembled could provide a good basis for further improvements. Enough to assemble an almost complete motor or two put it that way.

Port mapping i've done on a few cylinders, which unless i've made a massive mistake with the measuring seem to vary a little bit with all of them. I kind of expected as much. Without getting too bogged down with the theory side of things here, i shall play things slowly for a while until i have a better idea of where things need to be with regards to timing. Port timing that is...

Is lightest weight (reciprocating parts) a good option? I've weighed different things, i've measured different things, all with quite big differences. Which way do i go? Heavy or light?

Con-rods i have a range, most in pretty good workable condition, but after some recent comments i've listened and inwardly digested.
Cranks, most of what i have are within specs according to BS, and again after recent comments i've listened and taken on board what you've said. But i'm still just a little bit curious all the same, but i will start looking for something more up to the job. Same with crank bearings.

Question: how do i measure primary compression? (do you mean combustion chamber compression)
I can measure the compression in the combustion chamber, but not the crankcase. I need more information about this please.
Another area i'm interested in is the combustion chamber itself for obvious reasons :P Would this compression measurement be leaning towards how far i can re-work the combustion chamber?


I've had another idea with using a much smaller gearbox which never got fitted to 102's which involves a block of aluminium which will end up being effectively a big spacer, so i can use a slightly bigger prop for this "small gearbox". Better gearing with this smaller gearbox as well. I reckon some of you might know what i'm hinting at here 8)
Any help here would be appreciated with a few things. Just an idea at the moment but a definite maybe.

I will have a look for those topics dealing with props, and i promise i will pay attention.


Maybe i do spend too much time with the theory side rather than the physical hands on side at the moment, but i like to know that what i'm doing will be fairly safe without ending up in a pile of bits. You can't blame me for that can you.
Yes, i waffle on from time to time. Sorry about that too :roll:


Nothing will happen just yet as i've got another shed being delivered tomorrow to replace the current shed i'm working from. It's 20 years old and about ready to fall down on its own so any hands-on measuring won't likely be for another month or two. I might be away from the forum for a few weeks whilst i'm doing this. Give you some peace and quiet :oops:


All good

Jon

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Re: Modified 102

Post by GarethJ » Wed Jan 17, 2018 11:16 am

Measuring everything is well covered in this book;

http://www.google.co.uk/url?q=http://ww ... 65I9G7tFUB

Including the primary compression ratio, which is easy to achieve with basic tools.

It's worth reading through this/other publications before you start so you have an idea of what to expect, what can be applied to your machine and how everything is interconnected. It will be useful to go through the calculations with a "test" engine but as mentioned, you might as well start with one that is performing as well as can be expected so maybe skim the maths until you have a starting point machine you can tear into.

For example, you may be able to rule out your hidden exhaust idea by following the exhaust design section. You may find that a pipe that's expected to work at the rpm a stock crank can handle will no way fit into the space available. Or maybe it'll fit perfectly

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Re: Modified 102

Post by headdownarseup » Sun Feb 04, 2018 7:36 pm

I'm reading lots and learning lots.

I still like the idea of trying to accomodate a "tuned pipe" within the stock seagull exhaust tube. And to that end i think i might have found something that will work after a little fettling to make it fit. I will probably have to lengthen this "pipe" and alter some other things besides so it suits the characteristics of the seagull a bit better but it's looking promising.
The other mechanical bits inside the crankcases will of course come in for some careful examination. I'm trying to find a suitable crankshaft and rod that's right for adaptation into the seagull crankcase, just like those shown by Charles a bit earlier in this thread, but as yet no luck, so i'm now looking a bit further afield.

Nothing on this project will start in anger just yet as i'm in the middle of tearing down my old and rotten shed to make way for a new and improved building.
More coming a bit later


Jon

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Charles uk
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Re: Modified 102

Post by Charles uk » Sun Feb 04, 2018 8:05 pm

Not sure what your talking about jon
just like those shown by Charles a bit earlier in this thread,
I haven't posted anything on this thread!
Make it idiot proof and someone will make a better idiot.

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Re: Modified 102

Post by headdownarseup » Mon Feb 05, 2018 12:47 am

Sorry, no it wasn't you was it!
It was Gareth wasn't it. Silly me :roll:

It's late, that's my excuse

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Re: Modified 102

Post by GarethJ » Mon Feb 05, 2018 6:39 pm

Maybe you are thinking of the engine with the the honda crank over in the other thread. Don't think I've posted anything crank related here. Either way, you'll need a reasonable lathe as a minimum to do a similar swap.

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