How much speed do we lose due to fouling?

[woodie1000]

I'm interested to hear how other people suffer from this. We moved our boat from Menorca to the South of France earlier this year.

The fouling wasn't too bad in Menorca - from a supposed top speed of 32 knots we'd only ever manage 29 and late in the season this would be down to 27 or so.

It seems much, much worse in the South of France. From the usual 28/29 early in the season we're struggling to get past 22/23 now. There is a decent amount of fouling on props etc (barnacles as well) but I'm worried this is an engine problem as well as a fouling problem.

We had the filters changed earlier in the season due to a low fuel pressure warning. That cured the warning but there may still be another problem - we're down to 2,200 revs from 2,400 at max throttle as well.

How do others suffer in the Med? Is this type of speed reduction normal?

 

[Nautorius]

When I lifted the big girl her hull was not too bad but the prop was covered in barnacles. We got an extra knot afterwards which is about a 12.5% increase! Mind you when cruising speed is 6.5 knots every knot helps!

Paul

 

[DavidJ]

Don't worry, you don't have an engine problem. Your experience is quite normal for us in North Med Spain. I've found that 90% of the significant speed drop is barnacles on the prop. I'm fortunate with the Sealine that I can raise the legs, hang over the bathe platform and scrap the little blighters off. It's not easy but saves a £100 liftout. Then it's back to 32knots (from 22/24 ish knots)

 

[MedDreamer]

The effect of fouling on the props can be quite dramatic. In Alcudia I usually lift the boat April/May and by July the prop fouling can start to have an effect and by August was loosing about 7 knots. Got the snorkel and scraper out, cleaned the props and bottoms of the legs and back to full performance. Had to do it again last week though.

It happens most years, not helped by the fact we only use the boat approximately once a month giving thre barnacles plenty of time to get hold before the props turn again to shake them off. Two years ago fouling was much lighter, apparently because the water stayed cooler during the summer. It's been worse the last two years mainly, I believe, because I changed moorings and now the stern is facing south and the legs get the sun on them all day.

Clean the props, you will be amazed

Martyn

 

[Bandit]

29 percent

MBM did an article in June 2009 issue on fuel saving they took a Princess 430 and measured speed and fuel consumption after a year in the water and again after a lift pressure wash and antifoul.

I re worked their figures to give me litres per mile which is the real crux of the matter and after a year in the water you burn 29% more fuel per mile. Assuming that most people like me do destination boating ie to point a and back to base then with a dirty hull you burn 29% more juice.

I keep accurate fuel burn figures per re fuelling and i can see this in my fuel burn figures.

I used to work with fast ferries and now liesure boats it is suprising on a motor boat what looks like light fouling slime and a little bit of weed does to the speed and handling and on a yacht how a dirty yacht sails like **** it is sluggish and responds poorly.

 

[woodie1000]

Thanks for the replies everyone.

I was hoping it was the props - and from previous threads on here I thought it would be.

The problem is we're on shafts and I'm not sure I can hold my breath long enough to get under there to clean them!

I'm very interested in the diving gear that was talked about recently (Hurricane and co.). Sounds like a great solution to the problem and has the potential to add some fun as well. In the meantime, those that pay divers to do the cleaning mid-season, what is the going rate?

 

[SeaDave]

Don't worry, you don't have an engine problem. Your experience is quite normal for us in North Med Spain. I've found that 90% of the significant speed drop is barnacles on the prop. I'm fortunate with the Sealine that I can raise the legs, hang over the bathe platform and scrap the little blighters off. It's not easy but saves a £100 liftout. Then it's back to 32knots (from 22/24 ish knots)

Might be a silly question but what do you use to scrap the props?

 

[Firefly625]

Might be a silly question but what do you use to scrap the props?

a scraper..?

...sorry, couldn't resist!

 

[blueglass]

definitely sterngear fouling is the prob, not sure how much is props and how much rudders. In greece our max speed (semi d hull) drops from 18 knots in april to 10 in October if not cleaned. as regards what to scrape with - I use a scraper! i.e ordinary paint scraper. v difficult but just poss with snorkel gear.

 

[MedDreamer]

I use a wallpaper scraper and a heavy duty pair of gardening gloves

 

[Nick_H]

Hi Woodie, nice to meet you and the family last week. It's defintiely prop fouling. Our props were clean at the end of August, and we could get 28 knots+. Last week we were on the boat again and could get 20 knots max. I went under with the diving gear and there was a thin layer of barnacles on the stern gear. I scraped the props and hey presto, 29 knots on the way back. That's why you see so many posts on here about different prop treatments, because as someone else said, 90% of the speed loss from fouling is down to just the props.

 

[jhr]

The fouling wasn't too bad in Menorca - from a supposed top speed of 32 knots we'd only ever manage 29 and late in the season this would be down to 27 or so.

Air temperature can make quite a difference to speed - the warmer the climate, the less power the engines develop, which might account for the failure to hit top speed. But I agree - it's mainly the props. I've seen a marked difference, even in the UK, by lifting the outdrive and attacking the prop with a scraper after a period of neglect.

 

[woodie1000]

Hi Nick, yes, nice to meet you all too! You planning on heading out before the end of the year? We're going to try and do one more weekend.

Sounds like some basic diving kit would be a good investment (as per the other thread!).The costs on fuel would massively outweigh the costs.

I'm also going to trawl through the anti fouling threads. I thought it was a strange forum obsession before as we've never suffered so much (4 years in the UK and 2 in Menorca). Now I will completely understand the many threads on the pros and cons of copper additives etc........

I was just really surprised to see such a big difference - a few knots yes, but I wasn't expecting to lose 9!

 

[DavidJ]

Might be a silly question but what do you use to scrap the props?

I use a B&Q/Homebase scraper with about a 30mm flat end (from memory). Make sure it's a stainless steel one or it will start to rust in minutes. I just took the sharp corners off with a stone to prevent scratching the props. Tie a string around the handle and your wrist because you will drop it!!

 

[Deleted User YDKXO]

I'm interested to hear how other people suffer from this. We moved our boat from Menorca to the South of France earlier this year.

The fouling wasn't too bad in Menorca - from a supposed top speed of 32 knots we'd only ever manage 29 and late in the season this would be down to 27 or so.

It seems much, much worse in the South of France. From the usual 28/29 early in the season we're struggling to get past 22/23 now. There is a decent amount of fouling on props etc (barnacles as well) but I'm worried this is an engine problem as well as a fouling problem.

We had the filters changed earlier in the season due to a low fuel pressure warning. That cured the warning but there may still be another problem - we're down to 2,200 revs from 2,400 at max throttle as well.

How do others suffer in the Med? Is this type of speed reduction normal?

Entirely normal. I once lost 900rpm and 10 knots speed in the space of just 4 months over summer solely due to sterngear fouling. I now use a diver 3-4 times a season to keep the sterngear clean. Apart from maintaining the speed, I reckon the saving in fuel covers most of the diver's cost. Be aware also that the barnacles will reduce the bowthruster efficiency considerably, block seawater intakes and stop the log impellor rotating so you need to do more than just keep the props clean
On the other hand, I have found that hull fouling (as opposed to sterngear fouling) is not a major problem if you use the right A/F paint. In Majorca, Titan Medium is widely used and seems to work well, even for more than 1 season

 

[Nick_H]

Be aware also that the barnacles will reduce the bowthruster efficiency considerably .... so you need to do more than just keep the props clean

Mike

I've solved the bowthruster problem. This year I took the bowthruster props off, cleaned and sanded them, then sprayed with Int'l prop-o-drev primer, and painted with trilux. No loss of bowthruster performance after a summer in SoF, and blades still clean. Just a shame that Trilux wont stick to the main props.

 

[Nick_H]

Woodie, yep it's worth having some diving eqp't on board, and soon pays for itself as the bandit diver in Vauban charges about 300 euro to spend an hour cleaning your stern gear. Usually needs doing 3 or 4 times a year, so it adds up if you have to pay him each time.

No plans to visit boat again at the mo', but that list of jobs ain't getting any smaller, so I suppose a working visit is required at some stage ..

 

[jfm]

I'm interested to hear how other people suffer from this. We moved our boat from Menorca to the South of France earlier this year.

The fouling wasn't too bad in Menorca - from a supposed top speed of 32 knots we'd only ever manage 29 and late in the season this would be down to 27 or so.

It seems much, much worse in the South of France. From the usual 28/29 early in the season we're struggling to get past 22/23 now. There is a decent amount of fouling on props etc (barnacles as well) but I'm worried this is an engine problem as well as a fouling problem.

We had the filters changed earlier in the season due to a low fuel pressure warning. That cured the warning but there may still be another problem - we're down to 2,200 revs from 2,400 at max throttle as well.

How do others suffer in the Med? Is this type of speed reduction normal?

Hi Woodie. Yes, as others have said, that's prop crud, nothing wrong with your boat. I'll PM you the number of the Antibes diver, called Antonio. Nice guy, but not cheap. you need his number in your mobile anyway cos you can catch a rope or something when manoeuvring (as Nick will testify!) so you might have reasons other than fouling to call him, and he responds v quickly

I dont find using the boat helps. I've crammed 2 seasons running into this year and my props are as bad as yours. I'm going to try u/sonic a/foul maybe

Also, the local shipyard AMC Treuhard (sp?) will lift the boat and jet wash it in the slings for something like e500. Maybe worth doing that?

I'll email you about the other thing soon, just busy right now

 

[longjohnsilver]

Thanks for the replies everyone.

I was hoping it was the props - and from previous threads on here I thought it would be.

The problem is we're on shafts and I'm not sure I can hold my breath long enough to get under there to clean them!

I'm very interested in the diving gear that was talked about recently (Hurricane and co.). Sounds like a great solution to the problem and has the potential to add some fun as well. In the meantime, those that pay divers to do the cleaning mid-season, what is the going rate?

I regularly clean my props without dive cylinders. You will need thick gloves, a mask (I don't use a snorkel, don't like them) a scraper of some sort if heavily fouled otherwise I use a stainless kitchen scourer. Takes me about 10 minutes or so, normally aim to do one side of one blade per breath. Not difficult with a bit of practice.

 

[Deleted User YDKXO]

I regularly clean my props without dive cylinders. You will need thick gloves, a mask (I don't use a snorkel, don't like them) a scraper of some sort if heavily fouled otherwise I use a stainless kitchen scourer. Takes me about 10 minutes or so, normally aim to do one side of one blade per breath. Not difficult with a bit of practice.

No chance with Med barnacles. Firstly, a scourer just doesn't touch them. You need a stiff pallette knife or a broad bladed screw driver and, second, it takes a lot longer as you need to force the implement through the critters. During my last visit to Majorca, it took 2 mates and I at least an hour to scrape the props and even then they weren't clean