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Speed Freak :-)

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Re: Speed Freak :-)

Postby rogerblack » Mon Jul 03, 2017 4:34 pm

:wavey

That's useful feedback, Douglas.

I run premium diesel whenever I can get it on both the motorhome and high mileage estate car and am familiar with the benefits. I know from monitoring the mpg that it pays for itself, never mind keeping injectors etc. cleaner.

I'd never thought of using premium petrol on the outboards - however, pardon my ignorance, but would it only make a difference on four strokes or would two strokes benefit as well?

:cheers
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Re: Speed Freak :-)

Postby Paul B » Mon Jul 03, 2017 6:02 pm

rogerblack wrote::wavey


I'd never thought of using premium petrol on the outboards - however, pardon my ignorance, but would it only make a difference on four strokes or would two strokes benefit as well?

:cheers

You can use premium in a 2 stroke as well, it will or should run better , I normally run my trials bikes on premium and they are 2 stroke. Just make sure you use good quality 2 stroke oil as well
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Re: Speed Freak :-)

Postby DouglasW » Mon Jul 03, 2017 7:39 pm

Hi Roger, I phoned the local Yamaha service centre this afternoon, just after your post to confirm that the advice was still the same. Richard confirmed your question and Paul B's experience that running higher octane petrol would not do any damage to 4 or 2 strokes. Indeed they would both pull better under load. No harm will be done and the extra detergents will be just as effective at keeping two stroke carbs clean. With modern 4 stroke engines that run leaner and require 3 minutes warm up on tick over before opening the throttle, the benefits are even greater in smooth running before the engine is fully warmed up. Richard said that since outboard electrics were now so much more reliable, the main causes of engines not running right are now carburettor problems (with overheating problems caused by poor maintenance a close second).

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Re: Speed Freak :-)

Postby rogerblack » Mon Jul 03, 2017 7:55 pm

Thanks PaulB and Douglas for the information. :thumbsup

Good to know I can use the expensive stuff in the outboard as well as the vehicles.

Not sure I'll get much more spending power in Sainsbury's with the double or triple Nectar point promotions on BP Ultimate for the Mercury
but as the actress said to the bishop . . . :lol:

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Re: Speed Freak :-)

Postby Pete » Tue Jul 04, 2017 8:52 pm

Martin wrote:Be careful with the super fuel Pete. The octane rating is a fair bit higher and your engine won't be designed to run on it.
Your manual will tell you which to use.


I have to admit Martin I was a little hesitant. My cousin said him and his mates all run their motorcross bikes on the super unleaded from Sainsburys, and they all swore by it...I only really tried it as the tank still had about 5/6 litres of normal in before topping up.
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Re: Speed Freak :-)

Postby Pete » Tue Jul 04, 2017 9:10 pm

DouglasW wrote:Hi Pete, that is a great speed to get from such a small outboard. :)

I run my Yamaha F6C outboard on my F-RIB 330 on premium petrol and have done so for over 100 outings. It runs just great. The manual only stipulates a minimum of 90 RON. Both the Yamaha certified dealer where I bought it and the Yamaha certified dealer where I get it serviced recommended premium petrol as it keeps the carbs clean and runs smoother. Unfortunately none of the petrol stations near where I keep the boat stock premium so I need to bring it from Glasgow. Last year when I ran out I had to use local regular grade petrol. I found the engine more difficult to get onto the plane and it would not reach max revs at full throttle with the standard prop and one person aboard and my maximum speed was 23km/hr. Using premium petrol the motor does hit max revs at WOT and consistently gives 25-27km/hr at WOT (depending on sea state) that's about 16-17mph.

My uncle has a 40 HP Suzuki four stroke on his RIB, which is 8 years old and has 550 hours on it. He was advised by the Suzuki dealer to run it on premium petrol because it would run smother and start better. At the beginning of each season it starts first press of the button.

Based on this experience I will continue to run mine on premium.

Douglas



Hello Douglas :D Interesting the dealer advised super unleaded, and from 23 to 27 is quite impressive. I was really chuffed with the way my little OB performed especially with my slender figure as well :D I'll stay with the super fuel for now and see how it performs when it's running 100% super, but I'd be surprised if it went any faster.
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Re: Speed Freak :-)

Postby Martin » Tue Jul 04, 2017 10:48 pm

Interesting theory's guys.. I guess I'm on a different thought train than the dealer and you guys..
A higher octane fuel will require a higher compression/temp before ignition to give a complete burn.
How you achieve that from a single cylinder 6hp is beyond my comprehension :LMT

Surely such a small engine would require a faster burn to optimise its performance?

My personal opinion would be to stick with the manufacturers recommendation as I'm sure they will have spent a lot of money and time on bench testing each model for reliability, consumption and emissions... I doubt the dealers will have done that. :thud
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Re: Speed Freak :-)

Postby Andy B » Tue Jul 04, 2017 11:08 pm

Martin wrote:I guess I'm on a different thought train than the dealer and you guys..
A higher octane fuel will require a higher compression/temp before ignition to give a complete burn.
How you achieve that from a single cylinder 6hp is beyond my comprehension :LMT

It's not just the fuel, Older 2 stroke engines don't like the modern oils for the same reason.
The engines don't reach the require running temps (especially in cold sea water) to clean burn.

Just ask Paul B when he was following my 1991 mariner running on quicksilver oil.... :D
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Re: Speed Freak :-)

Postby Martin » Tue Jul 04, 2017 11:10 pm

I'm referring to the original post regarding Petes 6hp running super/premium fuel, oils are another subject entirely :D
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Re: Speed Freak :-)

Postby DouglasW » Wed Jul 05, 2017 9:40 am

Martin>
"A higher octane fuel will require a higher compression/temp before ignition to give a complete burn."


Hi Martin I would not get too hung up on theory, open your mind and get yourself a tank or two of premium petrol and try it for yourself. :)

The manual (which comes in 12 different languages) says use petrol of a minimum of 90 RON. Since regular UK petrol is 95 RON, are you suggesting I should pour meths or paraffin in my tank to bring it down to 90? Of course not.

My first motorbike had an ignition advance retard lever and you had to use to retard the ignition when starting and to retard it if the engine pinked or knocked going up a hill under load. An E46 BMW 330i I ran for seven years had knock sensors and an engine management system that would adjust various engine parameters such as timing to make the best out of whatever RON of fuel you put in the tank. Shell's website says you will not get the best out of V power unless your engine management system is designed to adapt to the higher octane.

Clearly a Yamaha 6HP engine does not have an engine management system like that E46. However, premium fuel is not just higher octane. It contains many additives such as detergents, lubricants , corrosion inhibitors and agents to prevent carbonisation and to break down existing carbon deposits. Shell recommend V power for use in older simpler engines to benefit from these additives.

It is now the Scottish school holidays and here on Fleet Bay there are many people who are experiencing problems of their outboards not running at their best. A lot of these problems are fuelling problems and there are several threads on this forum including this one where you went straight to the carburettor as a likely cause with good reason. If you have an outboard at the maximum rated power for your SIB/RIB/F-RIB like your 20HP on your 375 F-RIB or my uncle's 40HP on his RIB or my 15HP Yamaha on my F-RIB 330 you probably may not notice if your engine is underperforming by a small amount. However, for people like Pete, Gurnard and myself who want to plane with a 6HP, everything has to be just perfect. On Fleet Bay this week one poor running 20HP 4Stroke was cured by replacing 2 year old petrol with fresh. Another 9.9HP 4stroke which would not start despite having run at easter was cured with fresh petrol because he had left the air vent on his fuel tank open and the tank completely exposed to all the sun we had in April, May and June all the best bits of the petrol had evaporated!! A 5 HP 2 stroke was fixed by cleaning out the jets in the carb.

Before I retired I was a scientist at Glasgow University and I spent my working life challenging accepted dogma and doing experiments to find better ways of doing things. For the last 6 years I have spent part of almost every day April to October out on the water in one craft or another and I am always trying to get the most out of whatever I am helming.

20170702-IMG_3660DEW.jpg

For example this is me windsurfing last Sunday in a F5/6 gusting 7. My GPS showed I was doing just over over 48km/hr when the best I have had out of my FRIB 330 with a 15HP Yamaha 4 stroke on totally flat water is 41.5km/hr. How did I manage that? Well I have been windsurfing since 1977 so that helps but I have only had that board for two years. There are so many variables to adjust: sail down haul and out haul, harness line length and position on the boom, mast foot position on the deck, foot strap position and size and shape of skeg. So I have experimented using my GPS to record speed and made notes of what changes and combination of changes have worked and it has taken about two years of effort to get maximum performance. I could just have followed the manuals and stuck everything in the middle position but I would have got no where near that performance.

Going back to my FRIB 330and 15HP Yamaha. It took almost zero skill and knowledge to hit 41.5km on flat water. However it took some considerable effort and time (not to mention a rev counter, tiller extension, blocks of wood etc) to tune the F RIB 330 with 6HP Yamaha to hit 27km/hr one up or to get it planing two up using a small prop. And that reminds me of another occasion when I am glad that I did not listen to the received wisdom of the Fleet Bay pundits. They told me that changing to the small pitch Yamaha prop would only increase the revs by 350 RPM (i.e. 1" =200 RPM). Instead I did the experiment myself and lo and behold the WOT revs went from 2400 to 5300! This was because the small pitch prop allowed me to get on the plane and so the "RULE" 1"=200RPM does not apply if the boat can't plane with the big prop but can with the small prop.

The 6HP Yamaha 4 stroke is not known for its quietness or lack of vibration but subjectively it runs smoother with premium fuel. Where I really notice the difference is how it pulls out of the hole when two up. Even with the small prop I sometimes can't get the 330 onto the plane with two big people on board with regular fuel as it just won't hit max revs, which it needs to, to develop peak engine power but with the premium fuel it revs more freely, I can get it planing on WOT at max revs and then I can back off the throttle to keep it on the plane. With the 15HP Yamaha 4 stroke I do not notice any difference in ability to rev getting out the hole with premium fuel. But where it is dramatically different is after a cold start. This engine is designed to run very lean and has an automatic choke. You have to let it warm up for three minutes before you attempt to open the throttle (the manual tells you so) but even at tick over it is very lumpy, threatening to stall. Using premium fuel the warm up tick over is much smoother as is the engine response to opening the throttle afterwards.

In the long term my uncle's 40 HP Suzuki's and even my own 6HP Yam's consistent smooth running and easy starting after the winter layups, I am sure is related to the use of premium fuel keeping, injectors, carbs, valves etc cleaner.

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