Panic moment - thoughts please

[gibbowolfie]

I've rceived some helpful advice in my current purchase from the forum. Just had a panic tho'!

Survey showed the boat acheiving top speed (reported by GPS) as 26kn @ 3600rpm on KAD32. Surveyor said due to underuse 58hrs in 24 months "engine still tight" and indeed we did see 26kn on way back at slightly less than 3600rpm. Should be max of low 30s from manufactures suggestion.

The logic seems OK based on my understand but I'd like to see if I can get that backed up so I feel more confident. Nothing else jumped out as bad about the motor.

Your thoughts?

S.

 

[sailorman]

wot is the designed engine rpm

if 3600 thats wot u got

 

[hlb]

I'm bloody amazed that you got anywhere naer manufacturers dsign speed.

 

[gibbowolfie]

Don't know what the max rpm design is. But 26kn seems a lot less than 32odd.

OK same question different tack. On a year old boat having done an average 50odd nm would you expect to be getting near the max quoted speed or not?

 

[RJL]

KAD32's should rev to 3800-3900.

Mine rev to about 3600-3700 which is a little low.
My P286 makes 35 knots, start of season, 1/2 fuel, no water. Down to 30 knots, end of season, fully loaded.

If the boat has only been lightly used, how clean are the hull, drives and props ?

 

[jimg]

Yes, I would have said so, I have had 2 new boats and both reached "max design speed" on day one.
The speed dropped later due to all the gear I put on the boat.
What revs were you acheiving at that speed?

 

[gibbowolfie]

3600 from a standing start to full throttle straight away.

Boat has stood still for 12months basically. So fuel contamination/staleness could be a factor.

I'm just trying to work out if a full service will sort it out or if there could be something more hidden away. Hence panic.

It's probably nothing tho'!

 

[gibbowolfie]

Oh we were four up too. say 350kg of blokes on board.

 

[landlockedpirate]

I would think that with the extensive fouling this is about as good as you would get. Problem is that, as some of us mentioned before, you have no idea wether this is hiding any other problems.

You did have 4 guys on board but i would guess you had very little other gear, no tender, not a lot of diesel, no personal stuff. Last 23 HT I was on did 32kts fully loaded at approx 3800 revs.

 

[Nautorius]

Hi Steve,

Mine will hit 32knots at 3500RPM. If you push it up to 3800rpm then you can add an extra 1.1knots. The fastest I have got out of her was 33.1knots, fully fueled and with full water. 2 Adults, 1 child, an inflatable, an auxiliaruy engine, 3 anchors (and a 5KG is satisfactory), + more safety gear than you could imagine. This was the speed tested with two GPS and my speedo read 34.1knots .When I got her she had not been used for 8 months and within 5 mins of starting her up I got 31.5knots. With old fuel. The hull is a 38knot designed hull so it can still shift a lot.

Basically the level of fouling you have will knock 3/4 knots off her, the rest could be an engine/outdrive issue. Never underestimate the damage that not being used and sat in Salt Water can do. Hopefully it is just a dirty bum. Get her lifted and blasted down to see how bad the fouling is. Did you get her lifted for the survey? Has she been cleaned?

I would get her Cleaned ASAP and then see if you have an Issue. The only reason a newish engine should be tight is if there is a problem!

Fingers Crossed

Paul /forums/images/graemlins/laugh.gif

 

[gibbowolfie]

She was lifted and pressure washed for the survey. The prop was shown to be minus paint. I have no idea about the fuel, it may be over 6 months old.

 

[Nautorius]

Great news that the surveyor lifted her. Was the speed test before or after the lift and jet wash? The fuel will make the engine a bit klunky, but top her up with new stuff (about £50) and she will run sweet within an hour. Also get some soltron (fuel additive...other brands available) as there may be some diesel bug.

Cheers

Paul /forums/images/graemlins/laugh.gif

 

[gibbowolfie]

Was pressure washed before sea trial but as I was not present can't say exactly how clean she ended up.

 

[[2068]]

If you start with a boat that should hit 30kts, that's often quoted with two people, and half tanks.

Add some hull fouling, and you'll lose maybe a knot. Less than perfect props (even small dings or barnacles can make a difference) that could knock off another knot. Four large people onboard (too many cakes), another knot.

Then again, even with perfect props, half tank of fresh fuel, a few more hours, and one up, it still just might not quite hit 30kts. My last KAD32 was one of those. It never quite made it to 3800 (3750 ish), and I had 29.8kts on the GPS, just never the magic 30. I put 500hrs on it, and nothing was ever found to be wrong.

dv.

 

[Nautorius]

Fair Point,

But I have exactly the same boat with the same set up, so it does a tad over 32knots.

In this case it should not be 6/7knots down on a 2004 boat that should hit 32/33 knots.

Cheers

Paul /forums/images/graemlins/laugh.gif

 

[thefatlady]

[ QUOTE ]
Add some hull fouling, and you'll lose maybe a knot.

[/ QUOTE ] Some years ago, I bought a badly fouled 18 month old 21ft Sealine.
On the first sea trial it reached 13kts and couldn't get on the plane.
The vendor had the hull pressure-washed.
On the second sea trial it reached 32 kts.
I bought it.
I then took all the antifouling off back to polished gelcoat.
It would then reach 42 kts.
I did some rough sums, knowing what the engine power and top speed should be and assuming a fouling roughness height of 0.5mm and a few other things and was staggered by the power loss that fouling would cause, even at 13 kts. Then bear in mind that the engine is also running at considerably reduced power.
Don't underestimate the effect of fouling.

 

[[2068]]

Ok, didn't know which boat it was. What props do you have fitted. A6's ?

Point is, if you have exactly the same setup, and are seeing 32kts at 3500, and he is getting 26kts at 3600, that does rather suggest that it isn't the engine, and maybe more to do with that giant squid hanging off the bottom /forums/images/graemlins/smile.gif Those props with "no paint" sound a bit suspect, too.

If it was an engine issue, I don't see how he would be pulling anywhere near 3600rpms...

dv.