Colvic Seaworker

[wombat88]

OK, so it is not a new boat by any means but it is not expensive.

In order to help me understand what I am looking at I'd like some guidance to help me recognise the difference between a MK I hull and a MK II. Vendors rarely make a distinction.

As I understand it:

A MK I hull is displacement. Engine is likely to be around 80-90hp, often Ford. Max speed will be around 8/9 knots.
A MK II hull is apparently 'semi displacement' and therefore one might assume a higher max speed and perhaps 20 knots.

Questions:
1) What engine size might be found in a MK II in order to achieve the above?
2) Do any of the boats have small bilge keels as 'standard'?
3) What year did the MK II arrive and was the MK I dropped then?
4) How can I recognise a MK II?

As an aside does anyone have any experience of the Maritime 21?

Yes, I'd love a channel Islands 22 or Orkney Pilot House etc but they are 2-3 times the price.

Ta in advance for words of wisdom.

 

[Kawasaki]

Wait for a Channel Island to turn up at the right price

 

[Dieselboatman]

From looking at a colvic myself, and seeing some for sale that I've been eyeing up either to buy or for ideas if I bought a bare hull

An awful lot of the 20 and seaworker 22 seem to have a bmc 1.5 diesel, especially earlier displacement hulls (the 20 is only available as displacement)

So 40hp or so is plenty for hull speed

Some have had Volvo penta engines fitted among others, and again 15~50hp seems common

The semi displacement hulls are flatter at the rear from what I can see, hence allowing them to plane a little

They tend to be running 2.5bmc engines and some ford 2.5 diesels
But 60hp plus


So basically if it's a 20 foot hull, it's a displacement hull and not actually a seaworker

If it's a 22ft, then it can be either hull type
Year of change I dont know

But perhaps a good rule of thumb is what engine is fitted! If its 50hp or so max, chances are it's a displacement hull as it doesn't need any more as hull speed is its limit

If it's got a 70~80hp or more engine, probably a semi displacement
And I believe they were commonly a 4.0 litre ford sabre




I am in similar situation, the channel island is meant to be a nicer boat etc, but also command more money
And maybe not to everyone's view, but I really like the Colvic styling

 

[Reel Time]

We had a Colvic Sea Worker 22 with a Perkins 4108 or whatever the number is. was happy to do 8 or 9 knots. It was a Colvic boat so assume a MK1. I looked at changing it to a newer Sea Hunter with a big outboard / stern drive. I took a look at the builders place somewhere near Exmouth. Allegedly, the newer boats were a lighter build up. The Sea Hunters had the shorter wheelhouse and therefore more deck space and go a lot faster - but at a cost. Didn't change in the end and stayed with the old boat. That was a good few years (and boats) ago.

Edit: Man Friday was the builder of the newer boats (thanks Google)

 

[wombat88]

Thanks all, will do more searching. I think there was a thread here about this a few years back.

 

[gordmac]

I would imagine for 20kn you would need a couple of hundred hp. As was said, the semi Hull will have a flatter rear section to generate a bit of lift, look at a few semi and full displacement hulls to learn what the differences are.

 

[wombat88]

This old thread has plenty of info. colvic seaworker 22

The thing that I find curious is that it would appear that around 30hp is needed to achieve hull speed which is around 8 knots...so why do lots of displacement boats have 85hp, mostly Ford, in them?

When it comes to the semi displacement boats they seem to have 150hp +. Maybe.

 

[gordmac]

Having briefly looked at repowering a friend's motor sailer the recommendation now seems to be 2 or 3 times the original power which was adequate for Hull speed. However in rough weather the lack of power means the speed is significantly reduced by hitting large waves, presumably with more power this wouldn't happen?
If you want to lift a semi displacement Hull for more speed you require a lot more power hence the 150hp+ you mention.

 

[longjohnsilver]

I would imagine for 20kn you would need a couple of hundred hp. As was said, the semi Hull will have a flatter rear section to generate a bit of lift, look at a few semi and full displacement hulls to learn what the differences are.

I used to get 18kts from a 140hp Mermaid in my CI22 which I believe is a heavier boat, so I’d imagine the same hp would get about 20kts in a Seaworker.

 

[Dieselboatman]

Also, a 30hp engine is flat out to maintain hull speed

For example, an FSD425 (transit diesel) makes 40hp at ~2100rpm, and 60hp at 3200rpm

So from what I have been reading, with a correctly sized prop, you would get hull speed at lower rpm, so the larger engine actually is more economical (not working as hard)

But as others have said and from what I've been reading, maintaining speed on a really calm day is easier than in rough seas, so the bigger engine has more power reserve to keep hull speed

100+hp seems to be for the semi displacement hulls, which need the extra power to get up on plane a bit and above hull speed


On a side note, a 2.5di transit diesel, is very easily modified to add a turbo charger and also larger injectors

In the van, there was a choice of 70hp and 76hp (n/a diesel), both used different injectors
Then 85hp, 100hp and 115hp
85hp and 100hp used different injectors
115hp was intercooled but used 100hp injectors

They also used a Lucas EPIC electronic pump on the turbo engines, but the n/a used the Bosch VE
But many turbo EPIC engines got converted to a VE mechanical (easy)

Now, the N/A engines can be turbocharged easily, and fuel pump adjusted for more fuel and removal of the HBA pin makes a big difference

And, this is the key bit, the Mermaid Marine (not sure on landings?) Engines used a bigger turbocharger than a road vehicle, VE pump
And 130hp marine injectors

So with a bit of fabrication and modification, it would be very easy to convert a 70/76hp n/a engine into a 130~160hp turbo diesel

Just in case you see a boat but engine is only a 70hp

 

[gordmac]

I can't imagine a normal air to air intercooler would be much use on a marine engine.

 

[wombat88]

Both boats available locally apparently have Ford 85hp lumps, one described as 'Sabre' which I assume was a marinising company with a logo of a dolphin over a prop? They look like quite different engines even taking into account shiny bits. I know nothing about these but would appreciate any comments/info. Herewith the ads, obviously at the moment I cannot go and look!

Colvic Seaworker, Near Havant - Ad 106930

Colvic Seaworker, Hayling Island - Ad 109005

 

[Kawasaki]

The Sabre is another Ford based derivitive
Nowt wrong with them
The two Seaworkers you are looking at are in the same price area you could get a Channel Island for
Having owned both
I would buy a Channel Island again

 

[wombat88]

These two may be 'toppy' but the Channel Island boats that I have found seem to fall in the £12-15k bracket and a workaday Seaworker seems around £5k

 

[gordmac]

Perhaps all the ci22 recommending we have been doing over the years has pushed the price up!

 

[Kawasaki]

Perhaps all the ci22 recommending we have been doing over the years has pushed the price up!

Could be!
Who knows where we are going with boat prices?
Don't start, there is already a thread!
I looked for a friend in 2019 and We found one with a single 140 in it for 10K, nice one as well
Over the last 4/5 years they have 'sold', not asking!! between 4 and 22K
One will turn up at right money I,m sure

 

[wombat88]

At the risk of going off topic somewhat does anyone have experience of the Maritime 21?

 

[Dieselboatman]

The Sabre is a 4.0 litre engine, not based on the transit lump

And I doubt an air to air intercooler would work great, unless you used something with a fan

However, an air to water one would work well, and would be easy to plumb in with existing raw water system

Being a diesel mechanic and former agri engineer, and having a passion for tuned turbo diesels, the tuning side of the engines is definitely no issue ?

It's the floaty boaty bit I am new to

 

[longjohnsilver]

At the risk of going off topic somewhat does anyone have experience of the Maritime 21?

Sort of, built locally in Teignmouth, Rob Humphreys iirc. Met him cruising in his Nimbus a few years back. . The Maritime is a pure displacement boat, so about 6-7kts max.

 

[wombat88]

Sort of, built locally in Teignmouth, Rob Humphreys iirc. Met him cruising in his Nimbus a few years back. . The Maritime is a pure displacement boat, so about 6-7kts max.

Yes, quite traditional but probably very nice for a harbour and inshore boat.