How Fast Is Your Boat? - Page 7

Nos4r2 · 15 July 2007, 23:09

I actually agree with that article for new tech engines. It's the recommended method for running in an engine with properly matched pistons/rings to the bore size.
I'd do the old type of 'one size fits all' running in which IS suitable for old tech engines in other specific circumstances though.

In essence Codprawn, you're right BUT there are exceptions. I get the impression you're quite OldSkool about your mechanicals.

Matt · 15 July 2007, 23:54

Yeh, but an ABC motor doesn't have rings and relys on expansion of the piston for a good seal. So they actually machine the pistone slightly oversize and rely on significant wear to bed it in. That's why if you WOT an ABC motor too soon it can damage it.

Disagree about the example of aircraft engines comment. Allowing any engine to warm up before WOT is good practice, regardless of age/condition etc.
And An aircraft engine being run in is very likely to be run at 100% very early in it's life - many aircraft require WOT on takeoff, and typically cruise in the 75% power range as no doubt you know. Hardly babying it to run in.

Quote:

Originally Posted by codprawn

Sorry but I think it's a load of crap for any engine you want to last a long time.

Dragsters use this method of running in - they start up from cold and hammer it almost straight away. Cold engines have much higher compression as the oil is so thick. The difference is the engines only run for a few seconds and then are rebuilt.

There aren't many engines around that rival glow motors for power to weight etc - they STILL advise proper running in.

The best example is to look at piston engine aircraft operating procedures - your life literally depends on your engine and you would never even think of taking off until oil pressure and cylinder head temp were up to spec.

You can damage an engine by being too gentle with it. You can get carbon deposits building up etc. This tends to be a problem with older people driving modern cars who never go over 3,000rpm. As long as an engine is warm and run in it's fine to go the rev limit in every gear!!!

codprawn · 16 July 2007, 01:26

Quote:

Originally Posted by Nos4r2

I actually agree with that article for new tech engines. It's the recommended method for running in an engine with properly matched pistons/rings to the bore size.
I'd do the old type of 'one size fits all' running in which IS suitable for old tech engines in other specific circumstances though.

In essence Codprawn, you're right BUT there are exceptions. I get the impression you're quite OldSkool about your mechanicals.

No I am not old skool - the engines are!!! There is little really new out there. Take away all the electronics and the engines haven't changed much. 4 valves per cylinder - variable valve timing - multispark - sodium cooled exhaust valves etc etc have all been around for a very long time.

I just fail to get excited by so called "advanced" engineering because it's nearly always been done before.

I was amazed watching the manufacture of the engines used in the massive new container ships. The massive engines would have been quite familiar to IKB!!!

fast fred · 16 July 2007, 11:48

Quote:

It's the recommended method for running in an engine with properly matched pistons/rings to the bore size.
I'd do the old type of 'one size fits all' running in which IS suitable for old tech engines in other specific circumstances though.

this don't make much sense, pistons are fitted by what thay are made of, forged needin more room to run cuzz she will grow at temp more than a cast piston.

twice, steel sleeve and rings, heat them up twice and cool, thats as sealed as it gets, crome or Nicasil soon as the piston heats up you are thare.

a dragsta moda takes about 15 seconds to get to temp, in 90 seconds it would be a blob of melted ALU'

oilrig · 18 July 2007, 15:06

tornado 5.8 135 merc, 21p revolution 4 prop, 100 ltrs 2 men. 47 knts

Biggles · 18 July 2007, 15:46

Quote:

Originally Posted by oilrig

tornado 5.8 135 merc, 21p revolution 4 prop, 100 ltrs 2 men. 47 knts

Fast

Jon Brooks · 22 July 2007, 23:05

Well took the boat out for a raz between trips today.

Sea state flat-ish.

2 on board, half tanks so about 180lts.

Brought her upto about 5,600 rpm.

GPS speed of 50.6knts.

This was not WOT still a good bit to go.

Cheers

Cookee · 12 September 2007, 10:00

Our race RIB managed 84 mph the other day - anyone beat that?

7.4 metres Mercury 2.5 EFI (280 HP) 2 passengers (that's all it'll carry!) Tempest 23 slightly tweaked, modified gearbox, 15" offshore leg, over half fuel (at least 80 litres).

bedajim · 12 September 2007, 11:07

Quote:

Originally Posted by bedajim

Vipermax 6.5
200 OptiMax
21" Laser 2
150 litres fuel
2 people
flat water
48.2 kts
5200 rpm

New 21" mirage plus to test soon

New prop fitted
3 people
200 litres of fuel
calm water
5200 rpm

48.8kts but a little more to come with trim etc(better econ at normal speeds)

bedajim · 12 September 2007, 11:08

Quote:

Originally Posted by Cookee

Our race RIB managed 84 mph the other day - anyone beat that?

Only on the A34 going home

Cookee · 12 September 2007, 11:20

Quote:

Originally Posted by bedajim

Only on the A34 going home

You're welcome to come for a ride and see for yourself if you don't believe me - you can also ask anyone down here and they'll tell you that speed is genuine - we were dong 83 mph in the Salcombe basic race on Sunday!

Our leisure version (the 770) with a Verado 250 on does 64 mph as well.

And the slipway is only a few hundred yards from my house!

GuyP · 12 September 2007, 11:26

Quote:

Originally Posted by Cookee

we were dong 83 mph in the Salcombe basic race on Sunday!

Cookee - I don't suppose you have any pictures of that race you could post? I'm not doubting you, I'd just like to see a race in Salcombe Harbour

Mugshot · 12 September 2007, 11:49

Quote:

Originally Posted by Cookee

You're welcome to come for a ride and see for yourself if you don't believe me - you can also ask anyone down here and they'll tell you that speed is genuine - we were dong 83 mph in the Salcombe basic race on Sunday!

I could be wrong here and am obviously speaking for someone else, but the reply by bedajim gave me the impression that he meant the only way he would beat your speed would be when HE was on the A34 going home, not that that was where YOU achieved that speed.
Could be way off the mark of course

Nick Hearne · 12 September 2007, 12:08

Quote:

Originally Posted by Mugshot

I could be wrong here and am obviously speaking for someone else, but the reply by bedajim gave me the impression that he meant the only way he would beat your speed would be when HE was on the A34 going home, not that that was where YOU achieved that speed.
Could be way off the mark of course

Yep that is the way I read it too!

PeterM · 12 September 2007, 12:13

2 up 50 L fuel .- I thnk the slowest on here 31knts and I'm pround of that !

All in a little 4m boat with just 50 hp 4st yam . very flat sea needed

You dont need to do everything quickly to have fun ( but it helps! )

HoveRuss · 12 September 2007, 12:29

Ribtec 585 with Mercury f115 4 Stroke. 2 of us plus 80 litres of fuel, 38 knots at 5200 revs, starting to pick up a few revs, and a few knots as it runs in.

I thought it'd be quite fast enough for a newbie, but its so bloody stable at that speed it could do with a bit more!

Compares badly to my 35bhp, 4 stroke, 3.1 Metre Hovercraft which manages 40mph and burns 2 gallons an hour LOL!

bedajim · 12 September 2007, 12:31

Quote:

Originally Posted by Cookee

You're welcome to come for a ride and see for yourself if you don't believe me - you can also ask anyone down here and they'll tell you that speed is genuine - we were dong 83 mph in the Salcombe basic race on Sunday!

Our leisure version (the 770) with a Verado 250 on does 64 mph as well.

And the slipway is only a few hundred yards from my house!

Oh i do belive

No thats the only way mine will do that speed, on the trailer but I'll hold you to the ride

James

Cookee · 12 September 2007, 13:34

Quote:

Originally Posted by bedajim

Oh i do belive

No thats the only way mine will do that speed, on the trailer but I'll hold you to the ride

James

Sorry James!

You'd be welcome any time!

Tony · 12 September 2007, 14:51

i have just under 50 knots in mine...but the question is ......from 40 to 50knots is a a hell of a difference, to me 40 is a great fast cruising speed with eyes wide open. surely 50 to 70 knots is just darn right scary? Can a rib handle that speed over average waters for a period of time?
Tony

Nick Hearne · 12 September 2007, 15:02

Quote:

Originally Posted by Tony

i have just under 50 knots in mine...but the question is ......from 40 to 50knots is a a hell of a difference, to me 40 is a great fast cruising speed with eyes wide open. surely 50 to 70 knots is just darn right scary? Can a rib handle that speed over average waters for a period of time?
Tony

Ask John Fuller on Botmad!

Nick