Diesel for Llittle Boats

[The Woo]

Yep absolutely. The base Ovlov engine is quite sturdy if they don't get hot, but as you say, their alloy housing heat exchanges are a complete joke. it doesn't take long for salt to start mixing with fresh!
KEEP IN MIND, the aftercooler on B and C series Cummins are better, but only just. Definately pull them apart, clean, re-"o"ring, and reassemble while greasing liberally with a high quality and sticky marine grease. It really is one of the very few weak points to these engines (along with the laughable raw water pump situation from a longevity and servicability viewpoint, quite easily remedied if you act Prior to install).

[No Fear]

Interesting thread all. Some well priced boats in amongst them as well.
Not that I am the most mechanical minded person in the world, but I am running a 200hp volvo diesel in my 7m cat. My cruising speed is pretty well right on 20knots and around the 3000 rev mark - I could ring its neck a bit more and get 22-23 knots out of it but its an older motor (1999) and having been sitting around for a few years, trying to look after it a bit.
Certainly I would love another 5 knots on the speed but having now been on a few trips across the bay in sloppy 1m seas, 20knots is plenty. The boat handles basically the same in those conditions as when it is a millpond.
I havent exactly worked out fuel figures but I am estimating around 30-35 l/h at cruising speed. Trolling for 8 hours doesnt even move the fuel gauge so like you smithy, would love a fuel flow gauge.
I too thought 200hp would be a bit underpowered to push such a heavy boat. Having been in an outboard powered cat, that certainly are completely different boats. The diesel just seems to punch through anything but the big difference is the duo prop. Getting on the plane is nothing and the torque is unreal. Spot82 has nearly thrown me out of the back of the boat a few times changing spots and I have nearly put myself through the windscreen putting it in reverse while docking it.
As I said, would love a bit more speed but I like the way the boat handles. For the money that I forked out for it, I wouldnt have got a new 5m boat let alone anything bigger.
This engine will hopefully get me through 3-4 years and will decide if a repower is the best option. Would love to fit in twin diesels but a 315 is more likely.....
Any yeah - leave the shark cat owners alone!!!

[Midnight]

Chop,
I went from Volvo to Cat, and the difference in price and availability of parts has been amazing. It is so nice being able to order ANY part from Westrac (or the USA) and not being terrified of the price. The Cummins are the same. Millions of them in service in many and varied applications, truck, industrial, marine.

Woo, did you get rid of the Sherwood raw water pumps? Go for the Seamax pumps? Glad to hear you are onto the aftercooler program. The QSB's are no better. A mate of mine just had an aftercooler fail, assembled dry in the factory and never previously be apart.

No Fear,
I think it is the torque and the efficiency of the duo-prop that gives the performance with a comparatively low 200hp. The torque you are making at 3000rpm will be oodles more than a pair of outboards making the same 150 odd HP. Torque is the key when you are trying to turn something.
Your Volvo will live a long and happy life at 3000rpm, so long as you can make a minimum of 3800rpm fully loaded, and you keep the coolers well serviced.

Cheers,
Myles

[The Woo]

No Myles, left the Sherwoods where they are as they will last two years at least. Then, just prior to the warranty running out, they'll fail, and we'll get another two years before changing to the SeaMax pumps. Would love to do them now, but the refit has been, shall we say, somewhat financially draining.

Aftercoolers, yep, done. At Least they're coated internally these days with what seems a pretty high density paint, should slow down the corrosion a few more years.

Before;


And after;


Milled up some 5/8" spacers too for the front left engine mount, so you can at least get the raw pumps off without jacking the engine and removing the mount! Crazy shit Mr Cummins... (Having said that, was never a problem on our old 210hp version, much smaller, but still shit, Sherwood pump on those).

[The Woo]

Sorry we got so way out of control and sidetracked there everybody!

[Midnight]

Good stuff, you're onto it!

Awesome job so far mate, just had a read on THT.

Cheers

[PB]

I can see why there isn't to many trailer boats around the 7-8m with inboard diesels now, getting everything to work the way we wanted is a pain in the butt, our mission was to design and build a 7.5m mid mount Diesel that can still be towed by a standard 4x4 and i believe we have come up with a great design. we where unable to get the motor under the floor as pushing the motor that far forward played with the hull shape to much and it would have been a pig of a thing, so the motor had to be moved Aft into the middle of the cockpit and stick out of the floor around 250mm but we still have around 900mm between the engine box and the transom giving full access for fishing from port to starboard sides. as the engine box is quite low we have incorporated a rear facing seat and built in storage, live bait tank, drawers, and prep station on top of the engine box.
Now just to bite the bullet and build 1.

[Tinlegs]

Great thread guys and really informative.

I've had small boat diesels ticking over in the back of my head for a while now as my good lady and I think about where we go next with our boating - she's a Sustainability professional, and the environmental impacts of larger boats are being considered in the mix.

Lots of questions have been answered here. Great contribution as always Smithy, Midnight and others.

Don't know anything about these, but it came up when I was looking out of curiosity for a trailerable diesel powered mono and from an internet glance looks a nice boat.

I like how the engine box doesn't intrude too much on the dancefloor and the overhang at rear doesn't look too bad. Where it does intrude is where I usually keep my fish box in my current O/B boat, so a change in fishing style wouldn't be much of a problem for me - that's very subjective though.

Anyway, another one to look at, and we all like to do that.

Seatime 2800

http://www.boatsales.com.au/boats-fo...294892288%2079

[PB]

This is a drawing of the first Preliminary design.

[The Woo]

Really, the walk-around engine box in the centre of the cockpit isn't a negative at all, MUCh preferable than having to fish around large outboard powerheads in my opinion.
The engine box can serve as a base for a multitude of things.
Game chair
Rocket launchers
Cutting board
Tackle cupboards
Rigging station
Live well
... the list goes on. Any of the above can successfully be incorporated above the engine, making a small boat, "feel" like a big one.

[myusernam]

agreed, pluss you have the advantages of possible eutectic refrigeration, deck wash etc.

[myusernam]

have any of you big boat guys considered running a bypass filtration system (I like the frantz) and getting the oil sampled, changing on condition rather than at intervals? Coulb be major savings and longevity advantages in it for you. Interstate trucks use them (or centerfuges), and get over a million k's out of their donks....

[The Woo]

have any of you big boat guys considered running a bypass filtration system (I like the frantz) and getting the oil sampled, changing on condition rather than at intervals? Coulb be major savings and longevity advantages in it for you. Interstate trucks use them (or centerfuges), and get over a million k's out of their donks....

I feel it's simply easier to just change the oil at intervals. Cost of oil really is quite small in comparison to most of the other costs with these types of boats.
If you were really doing a lot of hours, or had a fleet of boats, then maybe it'd be worth the effort. But for one boat, two engines totalling 30 litres of oil and two filters, not worth it.
If the tests show metal or combustion cotaminents in the oil, well, the engine's already got a problem that needs or will eventually need fixing.

[cormorant]

Even with the small donks we always sample the oil and change at intervals regardless ( smallish cost) as with Ovlovs you really want to know early so you can save up to take out a mortgage and buy parts!!!! Great for maintainance records and resale as well. Just too expensive in parts and downtime to let mechanical wear get out of control as it leads to many other problems fast. Keep it simple in the engine bay unless you are very large and can walk around in there. Hydraulics are another big advantage of the diesels as well in the past but electric/ hydraulics for ligher use stuff is now getting pretty good with bigger batteries and duplicate alternators.

[The Woo]

My point really was that with most common engines, used at apleasure rate of a couple of hundred hours per year, the actual internals of the engine is seldom going to let you down before MANY other things shorten the life of the engine.
A massive overheat or water ingestion from somewhere is usually the killer of engines, long, loooong before the bearings or rings have worn out.

When we ran our baot hard as a charter boat, upwards of 3,000 hrs per year, we did take samples of oil. Nothing was ever amiss inside, but we popped a couple of engines due to silly failures of boat design (gravity works on boats!) or just unlucky (blue-bottle jammed in the intake, paid skipper ignored alarm, throttled on as she slowed!)