Engine size.

Blue Shark · Member

Engine size.

LeeSpot · Veteran Member

Hi,

We used to run a 33 workboat with 500HP cummins, and topped out at over 27kts and cruised at 17kts all day long without any effort. A mate of mine has got a 33 sports fisher with a 300hp mermaid but he's running at 1:5:1 and will cruise comfortably at about 14/15kts. Balance is key - his fuel tank is aft of the engine, but he carries a lot of gear under the wheelhouse floor too. I'd say the gearbox ratio needs to change to get the higher speeds.

Cheers,
Lee

Blue Shark · Member

Hi LeeSpot,

Thanks for the reply.

I did contact Clements marine to ask about the prop and they said that a 1.98:1 ratio was unusual but that the prop sounded right. I have just removed the fixed trim tabs as they suggested so will be interesting to see what difference that makes when Blue Shark goes back in the water in April.

kees · Veteran Member

Think Lee is right,

33 Lochin's seems to react better on high prop shaft rpm's than on a bigger prop pitch.

low shaft rpm's + big pitch gives a high propellor slippage.

The theoratically speed of your prop = 23 kn. in reality 12 kn. = 48% slippage.

+ boat a bit nose heavy ?

Cheers,

Kees.

Martin · Senior Member

Hi Blue Shark, I had a Ford Sabre 280 in my Lochin 33 and only got 14 knots flat out and my gearbox is a ZF 2:1, similar prop

I think everyone here is right, change the ratio of the gearbox, lighten the load up front, get as much weight aft and see what happens.

Good Luck

Martin

KOF · Member

Hi Blue Shark,

sorry about my late reply - not sure if it still relevant. I have a Lochin 33 GDSV (so different model) with a 300 HP Mermaid Turbo Plus. I does 20 knts flat out.

André

Wingleburtbenglebink · Member

Hi all, I've got a 33 with a Tusker wheelhouse running a single Volvo tamd 70e 306hp. I use a twindisc 1.5:1 and a four blade prop which Clements spec.d for me (can't remember dis or pitch but maybe 20x22 I'll look it up). I get 18.5 knots at full throttle, but usually run at 8 knots to save the noise and fuel. Consumption is 2.5 gph at 8 knots. The Volvo is heavy and with the gearbox weighs in at 950kg. I carry 6 dive cylinders, small tender & outboard, loads of dive gear and 250 litres of fresh water, so quite a weight to drag around. Previously I would cruise at 12/13 knots and use 6 gph, but I'm only on private use, so a slower pace suits me better. I heard of a 33 running a single 300 Ford achieving 22 knots but I've no idea about keel arrangement on that boat.

Blue Shark · Member

Hi all,

Thanks for all the info, quite interesting to here all the differences performance.

I have seen a secondhand 1.5:1 gearbox come up for sale at a reasonable price, so if it will fit straight in then I might have to trial it next season. The engine and boat don't seem stressed at all on the odd occasions that I open her up to clear her through, so maybe a different gearbox and prop will make a difference.

Having removed the fixed trim tabs, she hasn't gained or lost any speed, but she's certainly a lot drier now!

Cheers

Padrig

fingers crossed · Senior Member

Hi Padrig.

What Lochin do you have?

Just wondered if you were planning on fitting any adjustable trim tabs or interceptor blades?

Horsepower in a Lochin varies enormously depending on what people do with their boats. Some have around 120 hp because of doing passenger trips for Bird and whale watching trips where slow speed is a necessity. Others have much more powerful engines, like a 575hp D9 or even twin engines because of travelling large distances to fishing grounds etc. In my previous 33 I had twin 370's which used to push her along at 30 knots if needed, obviously the fuel burn was much more, but we covered ground quickly.

Cheers.

Dave

Blue Shark · Member

Hi All,

its been a while, but after talking to Clements marine they suggested upping the prop size as she was under propped. They increased the pitch from 22" to 24". There has been a lot of maintenance undertaken on Blue Shark including replacing a rotten ring deck! But as a result she has shed a lot of weight, being used for charter fishing trips she has been stripped back to the minimum. As a result the cruising speed has gone from 9kts to 11kts at 2000rpm and a top speed of 15.5 kts (previously 12kts) at 2500rpm which is quite an improvement!

The engine is still over revving so there may be still scope for a different prop again, but it would have to be a new one as the current prop has been adjusted as much as it can go. There is a bit more work to be done to the Shark including a new galley area which will add more weight to the bow which isn't ideal so I will wait till this has been done and a few more sea trials before spending anymore money props.

LeeSpot · Veteran Member

Hi Blue Shark - your main issue is the gearbox ratio. It needs to be 1.5:1 - weight and weight distribution are all parts of the puzzle, but the gearbox is definitely where I'd be looking to make the changes. What weight is the boat?

Blue Shark · Member

Hi Lee,

Blue Shark weighs around 6.5t. The fuel tanks (2x 300litre) are both aft of the engine so the weight is all pretty much aft. When I spoke to Clements, they said that the most they could do with my prop was add 2" to the pitch, if I required more then I would need a new prop. The prop was only adjusted as it had been sent away as it had got damaged.

I asked Clements whether changing the gearbox to a 1.5:1 and matching it with the correct prop would give more speed, but they were pretty insistent that just changing the prop would be enough. I did look into a new gearbox from Mermaid Marine and was quoted around £4500+Vat for a ZF280A and considerably more for a Twin Disc alternative, which unfortunately I do not have the budget for. I am going to contact Clements again with some sea trial results and see what they recommend and will post on here. As I am using the boat for charter fishing trips, a bit more speed would definitely be a big advantage, but as it is my first year of operation with a lot of start up costs I wouldn't be looking to change the gearbox unless I have issues with the current one.

LeeSpot · Veteran Member

Hi,

It's a minefield - and I'm speaking from experience. We've started with a 180HP 6BTA, upped to a 212PH Sabre, then a 280C, then a 350HP that turned out to be a 275HP after being dyno tested. We've over revved, under revved, black smoked, blue smoked you name it. We gave up in the end and re-engined completely with a 500HP Cummins QSC coupled to a Twin disc 1.5:1 - 28kts flat out with an 18kt cruise even with 12 men aboard with all their gear, but she was a heavy lay up ex workboat from Eyemouth and the fuel burn was eye watering even though we covered some ground at that speed.

We went through all the prop diameter tweaks, pitch tweaks etc with the older engines, but Clements got it bang on the money with the 500HP setup and that prop never needed touching. Hope you get it sorted in the end, I know how frustrating it can be.

All the best,

Lee

Blue Shark · Member

Hi folks,

Not sure if anyone still on here but thought I'd update this post as it has come time to replace the engine. The Mermaid turbo plus is being replaced with an Iveco 420hp and Twin Disc MG5061 1.75:1, spinning a 23" x 20" hyperform prop (as recommended by Clements). The boat weighs 6.6t but 7.5t with passengers with a theoretical top speed of 22 knots.

The work should hopefully be complete by April ready for the new season and I will post results from sea trials.

fingers crossed · Senior Member

Hi Padrig, I'm still here....so that's two of us but not sure about anyone else.

Iveco 420 is a good size for a single and should give a good turn of speed with a reasonable fuel burn rate.....nice.

Be good to see a few pictures of 'Blue shark' if you can.

Cheers

Dave

LeeSpot · Veteran Member

Hi Padrig - Still here, and still boatless! Glad to hear you've decided on a plan for the boat, 420hp should push you along nicely. Is the Mermaid caput or still running?

Cheers,
Lee

Blue Shark · Member

Hi guys,

Blue Shark is running fishing trips through the tourist season an was in a bit of a mess when I got her, so each winter she seems to undergo a lot of refurbishment/improvement when time and money allow. I will get some pictures up once some of the work has been carried out.

The Mermaid is still running, but have decided to repower to give a little more speed to put the shark fishing grounds off the pembrokeshire coast within reach regardless of tidal size. Also the old fords although very reliable are a little smokey in their nature and no longer really acceptable given the competition, a little bit of smoke is just enough to tip someone over the edge when they were just feeling a little green! The engine is just having a bit of clean and then will be up for sale on find a fishing boat with gearbox.

Lee, did you use to own Ocean Star out of Liverpool?

Cheers

Pad

LeeSpot · Veteran Member

Hi Padrig,

We had a similar job on our hands when bought the boat from Scotland, she had been a workboat out of Stornoway and Eyemouth for quite a while. Sometimes it seems to be never ending doesn't it :)

We did used to have Ocean Star, sold her to a guy over on the IOW but I think he's recently sold her on. Dad was diagnosed with Dementia a few years ago so keeping hold of her didn't make any sense - it was an accident at sea that led to his diagnosis. 500HP cummins was powerful but very thirsty - we ended up with the QSC engine by accident, original order for a 450HP CTA was placed but Cummins sold it on by mistake to another client. The old fords are a smokey block compared to some of the newer engines, I know what you mean about the smoke, remember it well! :)

Cheers,
Lee

Blue Shark · Member

Well, the work has been completed and the Blue Shark is back on the water ready for the season (at last!)

The new spray rails have made a real difference to the ride and dryness and the new engine, gearbox and prop pushes her along at 22kts flat out at 3000rpm (although we had 28kts in the tide!!!) and cruising at 12kts at 2100rpm and 15- 17 kts at 2500rpm, should make a real difference to our fishing with the new grounds that will be easily accessible.

Hope you all have a good season, there is one very happy skipper now operating down in West Wales!

-- Edited by Blue Shark on Friday 17th of May 2019 07:52:06 PM

Martin · Senior Member

Well done guys Blue Shark is looking good

Hope you have a great season

Tight lines

Martin

Captainchris · Newbie

Hello all !

just bought a Lochin 33 from 1979

short wheelhouse

repowered with a volvo tamd 71B 385 hp

1.75 gear

and a 24x19 fourblade prop

do we have any other people here with the same setup ?

-- Edited by Captain

-- Edited by Captainchris on Sunday 18th of July 2021 07:18:44 AM

-- Edited by Captainchris on Sunday 18th of July 2021 07:25:10 AM

FrankJScott · Veteran Member

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