Have I got a problem ?

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billmacfarlane

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...because I'm not sure. Boat is an Maxi 1100 which is of average displacement and has an easily driven hull. Engine is a Volvo 2030 with a 120 Saildrive. I have an Ambassador Stripper fitted and a Kiwi prop set up by the British agent. Under power maximum revs is about 3200/3300 rpm and boat speed is 6.5 knots. At what I regard as cruising rpm, 2500/2600 I make between 5 and 5.4 knots depending on sea state/wind speed and direction. This seems slow to me as every man and his hound seem to motor past me. Engine has been serviced every year and starts first time and runs like clockwork. Do these figures add up or, as I think, I'm slightly underpowered ? If so any ideas ?
 
Seems par for the course to me.
I have a Volvo 2020 (18hp in my Westerly Storm - 33ft) and at cruising revs, 2200 rpm she doddles along at 5- 5 1/2 kts - ish, in calm water.
Mine is a little underpowered but I can live with it, especially as I am getting @ 1.2 litres/ hour fuel consumtion.

Have you felt that the boat has decreased in power recently or has it always returned this performance?
 
Same engine & Saildrive ... but on a Bav37 - so longer water line ... we get 7.5kts in flat water with a clean bum at 3000rpm ... oh - bog standard 2 blade fixed prop.
 
Same engine, same boat as Fireball. Similar performance except will rev to 3600 max.

You not getting full revs suggests prop is a little too coarse pitch. Flat water you should be able to get about 5.7 with 2600 rpm, 6.5 at 3000 and 7 at least at 3600.
 
Would have thought a bit slow. Starlight 35 with older 2003 + Saildrive, volvo 3 blade folding, flat water and clean bottom, 7.5 knts flat out. Cruising revs of 2600, 6.5knts.

Anyway, sailing is faster.
 
puddock said:
Looks like I could do with a bigger engine :confused:
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Before you get the chequebook out, check the prop efficiency. If you phone one of the prop companies and give them engine size, top revs, gearbox ratio, boat waterline etc they can tell you what your prop size should be. You can then decide whether you want to reprop - a lot cheaper than a new engine.

But I suspect boatload plays a part in your concerns; it's easy to pile on half a tonne of stuff, fuel etc and this materially affects speed. In the case of my own dear hull, a Bav 38, I reckon early season smooth hull and no **** gives me easily half a knot more. This slides away as the season advances and the essential reserves pile up in the lockers! LOL

PWG
 
puddock said:
Seems par for the course to me.
I have a Volvo 2020 (18hp in my Westerly Storm - 33ft) and at cruising revs, 2200 rpm she doddles along at 5- 5 1/2 kts - ish, in calm water.
Mine is a little underpowered but I can live with it, especially as I am getting @ 1.2 litres/ hour fuel consumtion.

Have you felt that the boat has decreased in power recently or has it always returned this performance?
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I think you mean a 2002. We also have a Storm OD and were given dire warnings when we revealed our plan to take the boat UP the French canal system from the Med. "You'll need more than 18hp to make against the mighty Rhone," they sqeaked.

In the event, no problem and at no time did we struggle to make progress. With our original fixed two blade prop we made about the same speed as you, but we tended to run at a whisker under 2000rpm to keep the noise down. Things got a bit slow if we had to butt into wind over tide but generally we were very happy -- especially with the fuel consumption.

This year we fitted a three blade Featherstream prop and so far have had only one outing during which the improvement in sailing performance was noticeable. Conditions were not really right to carry out any serious appraisal of cruising performance under power, but the astern performance and stopping power certainly seemed better,
 
Got a 2030 in a Starlight which is an identical weight to your Maxi but 3 ft shorter on the waterline. With a 2 blade folder, I get 6 knots calibrated in flat calm at 2600 rpm. Never tried to get it to 3600 rpm - didnt think it would do it and you shouldnt operate at above 80% anyway. Against a 20kn headwind we will be down to more like 4.5kn.

Basically, I think the engine is on the small size for that weight ans size of boat
 
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I have the 2030 and saildrive with a Volvo 3 blade folding prop in my Westerly Ocean 33, the standard engine was a 2020. I get 6 knots at about 2300 rpm with clean hull and prop and about 7.5 flat out. This gradually drops of by about a knot as fouling, usually just the brown slimey stuff, takes hold, I use prop-guard grease on the prop and this does pick up some marine growth which is probably more critical. Towards the end of the season I am probably looking at 2600 rpm for 6Kts.

Just a thought, but are you sure the log is accurate?
 
We've got a Bavaria 32 with Volvo 2020 amd Kiwi prop fitted. We find that we can make over 6 knots at around 2500 rpm. However, we found we needed 400 less revs after we stripped the antifouling off the hull down to the gelcoat and then re-applied antifouling again. A slightly rough surface to the hull seems to make all the difference.
 
Your Maxi 1100 is a particularly easily driven hull with a long waterline, the motoring speeds you are getting are much too low.
Finngulf 33, similar hull and foil shapes, much shorter waterline and overall, 29 hp D1 30 with saildrive and Volvo three blade folder. Cruising revs. 1950-2000 in flat water gives 7.2 kts. (verified on GPS) when she gets her regular workout at 3200 revs. she is doing over 8 kts. through the water though I usually wait to do this when she has to push against a fair bit of tide, I can get her to motor at 8.5 but the stern is really dug in then.
(The difference between A and B is 5 litres per hour so not done more often than once a month or so)
 
Bill

I've got the same boat, same prop, Ambassador rope cutter but with the D1-30 engine.
We get 5 - 5.5 knots at about 2000 revs, 6 knots + at 2500, all dependant on sea/wind state and a clean bottom! Most other 1100's I come accross have the Volvo folding prop which I suspect is a bit more efficient, although more anode hungry!
It does seem you're not getting quite the performance you should be, but if you're getting the revs from the engine, then presumably it's the prop that's not giving the drive?
 
Quandary said:
Your Maxi 1100 is a particularly easily driven hull with a long waterline, the motoring speeds you are getting are much too low.
Finngulf 33, similar hull and foil shapes, much shorter waterline and overall, 29 hp D1 30 with saildrive and Volvo three blade folder. Cruising revs. 1950-2000 in flat water gives 7.2 kts. (verified on GPS) when she gets her regular workout at 3200 revs. she is doing over 8 kts.
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But weight is important to speed max and the Finngulf is a very light boat at 4.5 tonnes against the Maxi at 6.2 tonnes.
 
PeterGibbs said:
Before you get the chequebook out, check the prop efficiency. If you phone one of the prop companies and give them engine size, top revs, gearbox ratio, boat waterline etc they can tell you what your prop size should be. You can then decide whether you want to reprop - a lot cheaper than a new engine.

But I suspect boatload plays a part in your concerns; it's easy to pile on half a tonne of stuff, fuel etc and this materially affects speed. In the case of my own dear hull, a Bav 38, I reckon early season smooth hull and no **** gives me easily half a knot more. This slides away as the season advances and the essential reserves pile up in the lockers! LOL

PWG
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I'm entirely with PeterGibbs on this. Admittedly, we've always had less slippery boats than a Maxi; but the right feathering prop not only uses the engine better, but gave us a knot more under sail in the Westerly Konsort, meaning less use of the engine in the first place. It's also better for motorsailing, as it adjusts to the amount of propulsion from the sails. (Mr FG was lucky enough to find advertising literature including an endorsement by satisfied customer, Mr G E Batty (my dad), for the prop on his Excalibur, so purchase authority was pretty much guaranteed.)
 
Bosun Higgs said:
But weight is important to speed max and the Finngulf is a very light boat at 4.5 tonnes against the Maxi at 6.2 tonnes.
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Ah, builders statistics!
With everything out and the mast off, the crane driver reported 5.1, I think there are very few boats that are not heavier than the builders specify.
 
Surely the idea would be to make the max hull speed at max revs with the cruising speed being at the point of minimum consumption for power delivered. Our 36 HP Bukh is most efficient at about 2400 revs and at that speed our 35ft heavy displacement long keeled pride and joy does about 6 kts in most conditions. That for me is about right and, when we have to fight the tide, usually at Portsmouth harbour entrance resulting from poor planning, we have some extra power and speed in reserve.
 
I've a Dehler 36 with similar displacement to the Maxi 1100, same engine, Volvo 3-bladed folding prop. In flat water I reckon on 6 knots at ca. 2000 RPM and close to 8 flat out. Your numbers seem a little on the low side. But I suspect my log is a little optimistic.
 
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