Re-Powering Weypago

Jul 13, 2018 | Technical

A week or so before Easter we were sailing Weypago around Lyttelton Harbour when we chanced to see, beating up the harbour, a very smart looking H28. We were running goose winged at the time but after a hurried conference we decided to pursue this fine looking ship and find out more. It took a minute or two to get set up and then we set off in pursuit.

We don’t get too many opportunities to sail with H28s down here and it soon became apparent we were going to have trouble catching this one. My crewman, Roger, is always full of ideas of how to improve sailing performance and we began to experiment, first with sail trim and then propeller drag and noted that speed and pointing ability did improve with the prop allowed to free wheel. (I normally keep it locked). Now, I am not advocating free wheeling your prop as this can cause problems with the gear box, but the exercise did highlight the effect of propeller drag.

Even with this little bit of extra speed , it wasn’t until the mystery boat eased off a little that we were able to catch up and exchange greetings. She was the “Molly Malone” and though she looked like a new boat in expert hands, her skipper said he was having their first sail after a long re-fit. Boy, Molly Malone certainly looked beautiful and her owners can be very proud of the job they have done.

Getting back to the original story, this chance meeting and the propeller experiments set of a chain of events which has lead me to consider repowering Weypago.

When I got home that night I dived into Boating Mag looking for an advert for a feathering propeller. It sounded pretty good so I sent off an E-mail enquiry to the manufacturer about suitability of their product for H28s. They replied that the H28, in standard form, did not have room to swing one of these propellers. They went on to say that modification of the propeller aperture was necessary to create the room, and that running a left hand prop (which meant the shaft would have to run in reverse) would give a more suitable gear ratio. This is because the engine is a 2GM20 Yanmar (18hp max @ 3600, 16 hp MCR @ 3400) fitted with a gearbox that gives 2.2:1 ahead and 3.0:1 astern. A mechanic friend of mine who has a lot of experience with this engine tells me it would not be a great idea to run it astern like this so for now, I have given up on the feathering prop.

However, all this talk of aperture size, prop size and reduction ratios prompted me to review the whole propulsion package currently installed.

One of the things about being Lyttelton based is that trips up to the Marlborough Sounds often involve a lot of motoring, so you want a good set-up in terms of performance, weight, and fuel load, and you certainly don’t want to have the fillings shaken out of your teeth or risk damaging your hearing with exposure to high noise levels for long periods. The purist will say “wait for the wind” but unfortunately in this modern age, we are compelled to live to a schedule and, barring inclement weather, we have to push on at best speed by all means available on this coastal passage.

Now, I am not entirely without experience in this area, having previously been involved in engines and marine equipment mainly to do with larger vessels, and, having completed two successful re-powers on my own boats, one yacht and one launch, I propose to consider the current installation and its draw backs, and then look at what might be done to improve the situation.

The Propeller

Len Gilbert, well known expert on high speed diesel propulsion systems, often stresses the importance of the propeller in any assessment of power requirements. When I first purchased Weypago her performance under power was very poor. This was because she was severely over-propped (14×10) 2.2:1 reduction which allowed the engine to develop only 2200 rpm maximum. This meant that the engine could produce only about 10 hp according to its performance curves and explains why the vessel could not maintain more than two or three knots with a decent head wind.

This problem is easily fixed, and I had the propeller re-pitched to 14×8 inches which then allowed the engine to develop its full potential power at 3600 rpm, improved the boat’s performance in all conditions and reduced fuel consumption.

However the very high shaft speed does create noise and vibration, and it is well known that small, high speed propellers are less efficient than slower larger propellers. So I wonder, while the engine can now develop full power at the flywheel, how much power is lost through the inefficiency of the high speed shaft set up?

Bearing in mind that the original design of the Compass H28 was around a 10 hp motor with suitable propeller, I strongly suspect that the current set-up does not make good use of the available engine power at all. It would seem that a smaller engine with a bigger reduction ratio and appropriate propeller might well produce similar performance.


As we know the H28 has very fine lines aft and does not carry weight well in this area. With my wish to locate gas bottles and one or two other items on the pushpit, it would seem desirable to reduce weight in this area if possible. A lower powered installation might result in a weight saving.


A lower powered engine may well be smaller physically and create a little more cabin space.


The engine I have, whilst very popular in New Zealand, is quite a dated design. I have watched other manufacturers introduce new “improved” models on a regular basis and no one can doubt there have been significant advances in engine technologies of all types over the last 20 years. Just take electronic engines and emission controls on diesel engines for example.


Well this is a sticky point. Some folks I know would take the accountant’s view that one should be careful not to over capitalise one’s boat. To others, myself included, messing about with and in boats is a main hobby and a source of much pleasure and enjoyment.

However, this exercise, when complete, may well be of interest to those H28 owners who are considering upgrading from 10 hp engines. At the very least you would expect that a lower powered engine (less than 18 hp) would cost less and if similar performance can be achieved that will be all to the good.

In the next edition I will cover the choice of engine, its features, and how they compare with the existing engine.

n the last edition I covered the main reasons behind my decision to re-power Weypago. Interestingly, in the August Boating New Zealand, is an article by Len Gilbert covering the exact same issue, albeit in a larger vessel, that was my major concern. That is that a Compass H28 with standard propeller aperture does not have sufficient room to swing a propeller large enough to efficiently absorb 18 horsepower plus. Therefore, similar performance and better efficiency can be achieved by down-sizing the engine to better reflect the capabilities of the propeller and the power requirements of the hull form. I also speculated that there might be other advantages such as reductions in weight and physical size for example. Well, I think I have chosen an engine that will deliver in these areas and several others as well.

It is the Lombardini LDW502M marine diesel engine, rating 13 hp at 3,600 r.p.m. at the propeller shaft. There are a lot of things I like about this engine, for example its physical size, especially the relationship of the engine mounts to propeller shaft, is only a little different to that of the old 2GM20 Yanmar, meaning the required installation modifications are pretty minimal. The Exhaust is on the other side, but this is only a matter of pushing the rubber hose over to its new location. The exhaust outlet diameters are the same. The throttle is in a similar location, the compressor and associated pulleys can go in the same place, so I will not have to de-commission the freezer for the installation. Likewise the oil filter is similarly located. And that’s where the similarities end.


Fresh water cooling:

The Lombardini is fresh water cooled via a heat exchanger on the port side of the engine. To me this is far better than sea water cooling. FW cooling is an optional extra on the Yanmar which, unfortunately, mine didn’t have. With the use of appropriate water treatment the whole cooling system will stay in much better condition.

Ancillary equipment:

The possibility of mounting the secondary fuel filter and stop/start solenoid remotely is very useful in that it will improve service access to both the filters and the raw water pump. Driven off the camshaft, the raw water pump is mounted on the upper rear of the engine. Remote mounting the fuel filter gives relatively easy access to the two allen head cap screws retaining the raw water pump, enabling easy removal for servicing.

Also, a sump pump with hose attachment via a banjo fitting, can be mounted in any convenient place for oil change purposes, quite an improvement on the old “stick it down the dip stick hole” method currently in use. It is also interesting to note that the fuel on/off solenoid has a manual over-ride making it easier to prime the fuel system.

Fuel injection system

One of the most delightful features of this engine is the fuel injection system. Many readers will have had the occasion to “bleed” their fuel systems, perhaps because they ran out of fuel, or perhaps had a damaged fuel line letting air into the system. It can be a bit of a messy, smelly business, and it can be a bit time consuming if you are not an expert. The Lombardini does not require bleeding as such.

Its overhead cam design incorporate “unit” type fuel pump injectors driven off the cam shaft. These devices serve the purpose of both high pressure pump and injector in one. The obvious benefit in this is the absence of a high pressure fuel pump which has to be maintained. But the second, and perhaps more important advantage, is that priming the fuel system is accomplished by simply turning on the key or using the fuel solenoid manual over-ride, and operating the fuel lift pump handily located on the starboard side of the engine near the top. Pumping for 30 seconds or less is all that is required to restore the system to operating condition after (say) running out of fuel. Imagine how handy this might be if you were in a tight spot! The pump circulates fuel past the injectors and then to a drain back to the tank. No fuel outside the system, no smelly hands! Starting

The Lombardini has a glow plug starting system which assures easy starting. My old Yanmar is a similar design in that it also has pre-combustion chambers but for some reason the manufacturers left out the glow plugs. It has always been inconsistent in starting, usually starting quite well when warm, but sometimes requiring a lot of throttle (over fuelling) when cold and needing quite a few turns as well! Which brings me to the next point, the Lombardini does not have a hand starting arrangement. Old salts will cringe at this, but you can’t have everything. Hand starting requires a heavy flywheel to give the require inertia, and with a heavy flywheel, you no longer have a light weight engine. There are other practical considerations. On her delivery voyage Weypago lost battery power. Use the hand start we told the skipper- impossible says he, the compressor gear is in the way! So much for that. In its time, the 2GM20 was considered a light weight diesel hence it does not have a large enough flywheel to give enough inertia for hand starting, so even if the was no compressor in the way, my mechanic tells me, it would be extremely difficult to get this engine to start by hand especially at sea. So the hand start, or lack thereof isn’t really an issue in my mind.


At 75Kgs the Lombardini is significantly lighter than the old engine, which is a bonus. This can lead one to wonder whether it is just a souped up version of some lower powered industrial engine, a common method of improving the power to weight ratio of pleasure craft engines. This takes us into the area of ratings which is a complex subject to say the least, so I will keep my comments brief. Broadly speaking, the greater the power taken from an engine, the shorter its life will be, hence different ratings for different applications. For example you may find an engine rated at 350hp pleasure boat use may only rate 185hp continuous for work boat applications.

For both situations the engines will be subject to unremitting load for the time they are operating, but the pleasure boat engine will do significantly fewer operating hours each year. A similar parallel exists between Automotive (intermittent load) engines and industrial engines which are subject to unremitting loads driving (say) pumps or generators. The automotive engine will have the higher rating because it is not subject to unremitting loads. It follows then that Automotive ratings would approximate pleasure boat ratings while the more conservatively rated industrial engines will be closer to continuous duty work boat ratings.

On enquiring regarding the industrial equivalent Lombardini engine I found that the ratings are the same, this is most definitely not a souped up industrial engine. Further inquiries revealed that in New Zealand , units of this engine family typically run over 5,000 hours between major overhauls and that 5,000 hours is the manufacturer’s recommended major overhaul interval. I am much comforted by this fact. It transpires that the weight saving is accomplished by better design and materials, not performance enhancement.


As luck would have it, the engine is available with a 2.6:1 reduction ratio gearbox. On referring the propulsion package and hull details to propeller maestro Dave Buchan of Nalder and Biddle in Nelson, we were able to establish that the existing propeller (14×8) should be a good match.

Engine mounts

The engine is sold with Polyflex mounts which I understand comply with Cat 1 requirements in the respect that if the rubber material fails and the boat is rolled, the mounts are designed in such a way that the engine will be held securely in place. It struck me that this is rather a thoughtful action on the part of the engine dealer.

Having gone through the reasons, done all the paper comparisons and selected the Lombardini LDW502M marine diesel engine, it’s now time to do the installation.The number one job, of course, is to remove the old engine. This is a fairly straightforward business, disconnecting battery cables, fuel and water lines, wiring harness, shaft coupling and engine mounts. Next, using a chain block suspended from a steel tube set across the companionway, I lift the engine a little and move it forward, then hoist to clear the cockpit deck and then, with a helper on the other end of the tube, lift the engine into the cockpit. From there, using the boom as a derrick and main sheet for lifting hoist the engine clear of the coamings and then, using a guy to keep control, swing the engine out onto the pontoon and lower gently. The whole exercise taking less than an hour and a half.

To install the new engine, just reverse the above procedure, simple as. But, hang on, I must have left out a few steps, it can’t be that easy can it?

1. As the old saying goes, measure twice and cut once. The first thing I did was to make a jig out of some scrap MDF. The jig was to simulate the key engine mounting information, the relative position of the output coupling to the engine mount locations and the position and height of the engine mounts and mounting beds in relation to the centre line of the propeller shaft. Plenty of measuring and doublechecking went in to this exercise and I felt I had the dimensions exactly right. For some strange reason, as a final check, I quickly compared the jig to the new engine and – woops! This doesn’t look right, oh dear.There is sometimes a little note on data sheets – specifications may change without notice- and, although I have never struck this before, it certainly pays to check. It transpired that the mounting arrangements for the larger alternator meant that the engine mount locations changed to be the same as that of the larger LDW702M engine. Fortunately, making the discovery early meant only the jig had to be changed and not the whole engine bed arrangement.

2. The next job was to sort out the compressor arrangement. I had left the compressor on the boat still connected, in the hope that I could make the change over without the need to re-gas the system. Taking measurements of the mounting points and relative location of the pulley, a bracket was quickly constructed with a suitable location for the belt tensioner. Next the drive pulleys were fitted using a simple adaptor plate.

3. Using the jig it was possible to pick up the dimensions for the engine beds. The main changes were that the mounts needed to be about 25mm higher for the Lombardini, a little more widely spaced, and a little further aft. Lots of doublechecking then the mounting arrangement consisting of heavy angle iron bolted to wooden bearers was taken away to the shop for modification. Once the engine mount landings were welded in their correct locations, the angle irons were reinstalled and the jig used to mark the engine mount bolt holes. The angle irons were removed, the holes drilled and tapped, and then refitted ready to receive the engine. Lots more double-checking. One interesting fact emerged and that was that the wooden engine bearers were not parallel to or in the same plane as the propeller shaft. So never take anything for granted.

4. New copper fuel lines had to be run, one supply and one return, and the fuel filter was remotely mounted beneath the starboard quarter berth.

5. Set up the propeller shaft to receive the engine. This involved purchasing a suitable RFD half coupling and flexible coupling, ready to fit.

6. Make sure the battery cables are up to the job and organise the cooling system plumbing. In this case the seawater circuit was from the sea connection, minimum size ½”, to strainer, to seawater circulating pump, to siphon breaker, to freezer condenser, to engine heat exchanger, to exhaust elbow.

7. I made the most of the opportunity to clean out the bilges, and added a bit of extra sound proofing.

8. And, finally, I reversed the procedure in the second paragraph.

One of the critical factors in an engine installation is alignment. Going for space saving, I made this job a bit awkward for my self having located the engine as far aft as I could. This meant the business of lining up the coupling had to be conducted with mirrors and by touch, working over the top of the engine. The half coupling and gear box flange have male and female mating surfaces machined on them.

So, leaving out the flexible coupling for the time being, the first job is to get the mating surfaces to line up with each other by moving the engine sideways and adjusting vertically until they are as close as possible. With a bit of luck, this will be your port and starboard alignment taken care of.

Next, by moving the half coupling away from the gearbox flange, say 10 or 15mm and with the aid of some inside callipers, measure the distance between the two surfaces, comparing top and bottom, port and starboard. The idea is to get all these distances the same so the callipers “feel” the same at each point. Then see if the flanges will mate easily and adjust, then repeat the process until both the gap is the same at all four points and the flanges mate easily. At this point you can nip up the engine mounts and fit the flexible coupling. Next, on goes the freezer compressor, almost spot on, one small mod required.

I am pleased to say that all the earlier checking paid off and the alignment was set up quite quickly.All that remains to do then is hook up fuel, water, exhaust and electrical systems, make sure the propeller is in its correct location, make sure the engine has oil and water, and that the transmission has oil and then- big moment – kick her in the guts. She goes, music to my ears, fantastic, but we’re not finished yet.I know engine rep Alistair Donaldson will be along to check my work and I would be mortified if I have made any serious mistakes. So I get back to more checking, looking for leaks etc, while running the engine under load alongside. Next time, commissioning and trials. Will the engine live up to my expectations? Will Alistair approve the installation? What else will have to be done to get the best out of this engine?

Mike Holibar – “ Weypago”