Lack of power - only due to fouling?

[chrisharris]

Hi All, had a great trip out yesterday, boat is a Fairline 45 with TAMD71a engines. She is did out of the water in a couple of weeks for a scrub, and clearly has some corral worm on props and rudders. She performed actually quite well, but really struggled to get up to speed, engines were really slow (actually could not get beyond 1300rpm at any throttle position, then eventually started to creep up at part throttle - I very deliberately did not leave the throttles pegged at max!) to get above approx 1300rpm, below the point the turbos start to kick in. Normally I would just think this was fouling, and once the rpm started to climb and the turbos cut in she got to 2000rpm ish max (I ran at about 1700rpm not to overload the engines too much). My only niggle is that whilst I was asking for more power, but not accelerating, there was no black smoke - not a trace. Just wondering if there might be a fuel issue as well as the fouling, I have changed both pre and engine filters recently so would be surprised if that was a cause. Given the simple mechanical nature of the engines I would assume they would not have the ability to restrict fueling if the turbos were not boosting?

 

[madabouttheboat]

I would put money on your problem being 100% due to fouling. Get it scrubbed and then worry about it after a test run, if a problem still exists.

 

[Bandit]

When was she last pressure washed and did she have fresh anti fouling after that ?

Where is she berthed ?

 

[rafiki_]

At this time of year the white worm casts can appear overnight on the props and sterngear. These can hugely impact the efficiency, and need cleaning off soonest. On our Azi this could knock 10 knots off the speed.

 

[chrisharris]

When was she last pressure washed and did she have fresh anti fouling after that ?

Where is she berthed ?

Last July, and yes fresh antifouling applied. TBH I am not surprised about the dropoff of performance, just trying to square why the engines don't black smoke if they were being overloaded, I guess they don't overfuel if not on boost?

 

[jon and michie]

Was the boat working good before hand ?
I like the other have said put it down to fouling - I had this issue last year due to lock down and when I was able to get out it was slow as anything the following week even slower - when lifted for winter I got the marina to photograph the hull before washing and was full of slime - This year she runs like a dream.

Jon

 

[rafiki_]

Hull slime won’t make a big difference, it is the growth on the props and sterngear that have a massive impact

 

[jon and michie]

Hull slime won’t make a big difference, it is the growth on the props and sterngear that have a massive impact

My props and drive also had growth on - I should have said the whole underneath lol.

But seriously one week I got 2500rpm the next was 2300rpm
This year with more regular usage I'm getting 3700rpm easily.

Jon

 

[Portofino]

Hull slime won’t make a big difference, it is the growth on the props and sterngear that have a massive impact

Agreed it’s all about stern gear hygiene first then hull fouling second .
They ideally need a proper lift out preceding your season start , Fresh AF on the hull and what ever stern gear AF works for your boat / waters .End of.

Deviate from this strategy , tossing in “ I have not time “ “ it’s a short season “ “ will last years do ? “ “ I,am skint “ + a myriad trumped up Covid reasons put Fwds on this forum etc etc just will not cut it .

 

[jon and michie]

Agreed it’s all about stern gear hygiene first then hull fouling second .
They ideally need a proper lift out preceding your season start , Fresh AF on the hull and what ever stern gear AF works for your boat / waters .End of.

Deviate from this strategy , tossing in “ I have not time “ “ it’s a short season “ “ will last years do ? “ “ I,am skint “ + a myriad trumped up Covid reasons put Fwds on this forum etc etc just will not cut it .

I always clean up my props and re antifoul each season - unfortunately last year and by obeying the lock down rules i didnt get much boat time in as she is around 3 1/2 hrs away - so the boat sat dormant for a good period of time which led to the growth - Hence when she went back in this year I was very keen to find out how the performance was and was very pleased / relieved.
Jon

 

[oldgit]

Boat anti-fouled with arm and a leg "proper" Hard Anti foul in May.
First trip out 24.5 knots boat full of gear/fuel/ water . Whee..........
Speed slowly dropping off, 50 hours later down to 20 ish knots.
Faffing about in kayak over weekend able to feel under boat, already a perishing coat of soft slime on bottom with obvious fine slimey growth visable on top of trim tabs.
It only took 3 months.
Will probably revert back to Hemple Classic next time.

 

[rafiki_]

I always clean up my props and re antifoul each season - unfortunately last year and by obeying the lock down rules i didnt get much boat time in as she is around 3 1/2 hrs away - so the boat sat dormant for a good period of time which led to the growth - Hence when she went back in this year I was very keen to find out how the performance was and was very pleased / relieved.
Jon

The dreaded white worm casts can appear in a few days of sunny weather. I lost 10 knots of speed in a week a few years ago. I had to lift Rafiki mid season to clean the sterngear. Hull never a problem as she is copper coated.

 

[ari]

If the revs were the same on both engines then it's almost certainly fouling. It's unlikely that an engine fault that reduces power would affect both engines an identical amount, normally with a 'sick' engine, you'll see the revs lagging on one rev counter.

Beyond that, agree with the above, your experience sounds entirely how a boat that needs cleaning underwater would perform.

 

[jon and michie]

The dreaded white worm casts can appear in a few days of sunny weather. I lost 10 knots of speed in a week a few years ago. I had to lift Rafiki mid season to clean the sterngear. Hull never a problem as she is copper coated.

Last year and this year the U.K does seem to be hotter which is good when out and about on the boat - when sat dormant then this doesn't help - a neighbouring yachter said to my swmbo the other week that he is now scrubbing his hull every fortnight just lately from when he used to do it once a month.

Jon

 

[Mr Googler]

Last July, and yes fresh antifouling applied. TBH I am not surprised about the dropoff of performance, just trying to square why the engines don't black smoke if they were being overloaded, I guess they don't overfuel if not on boost?

there’s a smoke limiter attached to the intake manifold by a small plastic pipe. If you are not making the boost (as the revs are down) then the diaphragm won’t allow extra fuel….hence no black smoke.

Volvopaul explained it to me once and I think that’s the jist of it

 

[chrisharris]

there’s a smoke limiter attached to the intake manifold by a small plastic pipe. If you are not making the boost (as the revs are down) then the diaphragm won’t allow extra fuel….hence no black smoke.

Volvopaul explained it to me once and I think that’s the jist of it
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Ah, many thanks, that makes sense. I understand the issue with coral fouling, but could not work out why the engines did not appear to be over-fueling. This is the missing bit of info. Looking forward to getting it scrubbed in a couple of weeks!