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Old 12 May 2015, 07:08   #121
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Its going to make about the same difference to the boats overall performance as emptying your bowels before climbing aboard.
You must be a very large man then


If you really are trying to get the most out of the engine like you say, then that would mean you'd look at every aspect to gain more power. Polishing the ports and all of the other work you did is a hell of a lot more than anything I suggested.
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Old 12 May 2015, 09:31   #122
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Fair enough, what RPM were you operating at on the engine you did it with?
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Old 12 May 2015, 10:26   #123
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I wasn't concentrating on WOT as is your situation. I was looking for overall performance across the full RPM spectrum in an offroad application. Regardless of water or land, engines run under the same basic principles and most have the same performance enhancements available to them. At first I was working with an old carb system but with a recent engine swap, I'm tweaking fuel injection including the programming of the PCM/ECM.

For what you are trying to achieve I can safely assume you are concentrating your tuning for WOT. With your carbed system, this means you will have a terrible and rough idle, crappy general rpm but a robust high-end. You should be plotting and analyzing your timing, vacuum, fuel pressure, etc. underload vs not under load. Have you recorded your past specs and settings vs the improvements to see where you need to concentrate your efforts?

Polishing and porting is just one step in many and you won't see the full potential unless you adjust for the additional compression, timing, spark, fuel/air ratio, etc. Have you analyzed your intake and exhaust for laminar flow? Bigger doesn't mean better. Just putting in a better coil doesn't make much if any improvement unless you adjust everything else it's tied to, i.e: plugs, wires, gaps, etc. Everything has to be tailored for your specific application and any improvement you make.
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Old 12 May 2015, 11:17   #124
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You must be a very large man then
.
I'm a wee fella, I just eat alot.
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Old 12 May 2015, 12:27   #125
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i'm a wee fella, i just eat alot.
hahaa!
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Old 12 May 2015, 12:34   #126
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Neuner, I know what you mean about getting all the modifications in proportion to each other and tuning the engine to suit the new compression, porting etc.

It's a lot easier said than done getting it bang on, especially without a dyno. Although the engine operates mostly at WOT, it still needs to work lower down in the rev range. No point building an engine which is only good for top speed, has to work in the surf too on these boats

Everything you're saying is true, but there's a big difference between the theory of it and actually doing it and seeing the results. Thats why the factory put so many hours in R & D, most of the modifications I've done are to strengthen the engine so I can push it harder, rather than neccessarily increase the horsepower. The porting is suited to my boat, it probably wouldn't work on a heavier, displacement boat.

I really don't think the spark has that much effect, basically all it needs to do is ignite the fuel/air, which it does just fine.
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Old 12 May 2015, 15:56   #127
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Guess I misunderstood. With the postings about improvements, the top speed you achieved and a comment or two about getting the most out of the engine, then I thought you were getting prepped for racing. Your comment about the company's R&D research is dead on but contradicts the polishing, porting and changes in coils, carbs, etc that you made.

Not really that difficult to monitor and figure out just more difficult with a carb setup. Just depends on ones abilities and understanding.

With my current setup I tied in a bluetooth connection to the engine computer which gives me everything I could need and also graphs it out. I see they have it for EFI outboards but tends to run a little higher in cost. Great for live data under load.

There are plenty of professionals that will disagree with your comment on the spark, but then again, it has to due with ones abilities and understanding.
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Old 12 May 2015, 16:09   #128
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I don't think I did contradict myself. The manufacturer did all the R&D, but these engines are mass produced, which means they can't be tailored to suit each individual application. It also means there will inevitably be casting flaws, which is where polishing comes in. It's not financially viable for the factory to polish each crankcase, whereas I had time to do so.
The porting I did was only beneficial because of the nature of my boat, which weights around 72kg.

Welding the crank is because I'm pushing the engine harder than it was designed to go, so it needs strengthening to handle the additional RPM. Same goes for solid engine mounts, carbon reeds to prevent smashing the pistons etc.
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Old 12 May 2015, 16:15   #129
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I'm a wee fella, I just eat alot.
It's all that smoked venison and fresh lobster you scoff
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Old 12 May 2015, 16:36   #130
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I don't think I did contradict myself. The manufacturer did all the R&D, but these engines are mass produced, which means they can't be tailored to suit each individual application. It also means there will inevitably be casting flaws, which is where polishing comes in. It's not financially viable for the factory to polish each crankcase, whereas I had time to do so.
The porting I did was only beneficial because of the nature of my boat, which weights around 72kg.

Welding the crank is because I'm pushing the engine harder than it was designed to go, so it needs strengthening to handle the additional RPM. Same goes for solid engine mounts, carbon reeds to prevent smashing the pistons etc.
Okay - so why did you start this thread then in an inflatable boat section of a forum? Why not the devoted engine section? Were you just looking for pats on the back from guys who spend most of their time cruising a bay or river in a SIB fishing with an underpowered engine?

If you're really trying to make improvements it would figure you'd be posting on a thundercat racing forum instead of here.
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