| Changing the main engine of a boat sounds like a | | | | the bottom to catch any oil drips. Tip2: Cut up a |
| huge project. Cranes, plans, alignment, choosing | | | | piece of plywood to cover the floor around the |
| the right engine, it can all seems overwhelming to | | | | work site. Often times the new engine arrives in |
| the yachtsman. In reality for the DIY changing a | | | | a plywood box that can be cut up to use as |
| main engine in a yacht is relatively straightforward. | | | | material to protect the floors. |
| You don't have to learn all the special skills of a | | | | Engine Alignment |
| master mechanic as you never rebuild or even | | | | The final engine alignment is often the last tricky |
| work on the diesel engine. | | | | item on the DIY's mind. Will all the measurements |
| It's a simple matter of removing the old engine, | | | | be correct? Will the shaft simply slip onto the new |
| rebuilding the engine mounting rails, and then | | | | gearbox? By learning a few engine alignment |
| bolting the new engine in place. It might sound | | | | tricks you can save a big chunk of money and |
| complicated, but it's really rather simple. Do it | | | | time by preventing the rebuild of gearboxes, |
| yourselfers often take over three months to get | | | | broken shafts, or worn couplings. |
| their engines installed. I have devised a system | | | | Remember, if your on a new engine installation |
| outlined below where we can change a main | | | | we should align the engine before we make the |
| engine in just one week. The one-week engine | | | | holes to bolt the mounts in place. Only once the |
| change means the boat, and often the family | | | | engine is perfectly aligned should the first mount |
| living area is only torn up for seven days. | | | | be bolted down. Then the alignment is checked |
| Step 1-Buy New, DON'T REBUILD! | | | | again. If all is still correct then bolt another mount |
| This is a very important point. Boat owners will | | | | in place and so on till all the mounts are securely |
| often look at their worn out, leaking, engines | | | | bolted in place. |
| wanting a rebuild of the old trusted "friend". | | | | The first step to aliening an engine is to locate the |
| Unfortunately the numbers don't add up. Consider | | | | prop shaft in the middle of the stern tube. I like |
| that a rebuild job will normally cost about half the | | | | to start with the shaft just over center (at the 3 |
| price of a new engine. Most rebuilds only come | | | | 5ths mark) so as the flexible engine mounts sag |
| with a short term and local guarantee. In other | | | | over time the shaft will remain in the center of |
| words head to the islands and if complications | | | | the stern tube. You may have to block up the |
| arise the local mechanic that rebuilt the engine will | | | | shaft to keep it in place. Remember the engine |
| want the engine returned to his shop or marina | | | | aligns to the shaft. Once the shaft is in place the |
| for service. | | | | engine should follow, not the other way around. |
| I come across engines all the time on the cruising | | | | Clean both flanges using a wire brush. Push the |
| circuit that have five hundred hours after a new | | | | prop shaft flange against the gearbox flange. |
| rebuild. They are blowing and burning oil leaving the | | | | Ensure the centering rings set in place. Give the |
| owner back to square one. Besides, the price | | | | flanges a twist back and forth to make sure they |
| estimate I just gave is only the cost of rebuilding | | | | are seated well together. Slide a feeler gauge |
| the block. The old heat exchanger, oil cooler, gear | | | | between the flange faces. Measure and mark the |
| box, alternator, and high priced injection pump | | | | area of greatest gap. Before you proceed rotate |
| may still have five thousand original hours on | | | | the prop shaft one hundred and eighty degrees or |
| them. Rebuild all of the extra components and | | | | a half turn. Check the feeler gauge readings. They |
| your well on your way to the cost of a new | | | | should remain constant. If the readings changed |
| engine. | | | | from our first measurement then the shaft is |
| Measure before you pull the old engine | | | | bent or the flange is bad. If you find a bent shaft |
| Ask many "do it yourself" yacht owner about an | | | | and it exceeds the four thousands tolerance of |
| engine change and the sticking points will be: | | | | the alignment then fix that problem before you |
| 1. How to measure for the new engine. | | | | continue with the alignment. |
| 2. How to move the new engine. | | | | Often times we suspect the shaft is bent or |
| 3. How to make a perfect alignment. | | | | some other aspect of the drive system is out of |
| Lets start with how to measure. This semi-simple | | | | true. This simple shaft rotation test confirms the |
| process takes about two hours and is outlined | | | | problem or sets our mind at ease. Adjust the |
| below. | | | | engine mounts a bit at a time to close the gap in |
| The Measurement | | | | the flange faces. Keep all four mounts as even as |
| The measuring technique is the heart of an engine | | | | possible. Keep checking alignment till you are |
| change. The first thing you will need to do is find | | | | within.004". At that time tighten all the mounting |
| the existing height of the crankshaft center to | | | | bolts and check alignment again. Wiggle and shake |
| the bottom of the existing flexible engine mounts. | | | | the engine as much as you can. On larger engines |
| To do this take a flat edge and lay it across the | | | | you may have to get two people pushing and |
| engine beds. Use this straight line to measure | | | | pulling to get the engine to move around. The idea |
| down from the crankshaft center to the engine | | | | is to make the engine settle on her mounts. |
| bed line. | | | | Check the alignment again and adjust your |
| This is your first important figure. This is the line | | | | mounts to fix any gap that reopened. Keep |
| of the prop shaft progressed forward. If the | | | | repeating this procedure until the engine is sitting in |
| gearbox has an offset, or a drop, then you must | | | | perfect alignment. |
| add or subtract this figure to your final | | | | Expect to take about six hours to do a perfect |
| measurement. Now look at the drawings for the | | | | engine alignment. A good experienced technician |
| new engine and find the distance from the center | | | | can normally complete this process in about an |
| of the crank to the engine beds. Add in the | | | | hour. Of course this means all the bolts are loose, |
| gearbox offset if any and you should now have | | | | clean and access is easy. Tip- Resist the urge to |
| two separate measurements. The difference | | | | move a single mount that builds up a little |
| between them is the thickness you will have to | | | | pressure on the opposing mount to make a small |
| make up, or cut down from the excising mounts | | | | adjustment. When the rubber in the engine |
| to make the new engine fit. | | | | mounts get hot it will soften and fall out of |
| Simple Now that you know | | | | alignment causing the engine to begin vibrating. |
| Strangely after many engine changes with this | | | | Tip- If you find you have to lay on top of the |
| system I have not come across an engine bed | | | | engine to reach the flange to measure your |
| that needs to be lowered. For some reason they | | | | weight will almost assuredly change the |
| all have to be raised 10mm to 50mm. The | | | | compression of the mounts and thus your |
| difference between the old engine and new is the | | | | alignment. If this is the case then you will have to |
| all-important measurement. If you got this right | | | | find some clever way to keep your weight off |
| then you can have the "adapt a rail" pre-made | | | | the engine while you test the flange. If I have to |
| before you remove the old engine. Lift the old | | | | lay over the engine to work on it lay some |
| engine, bolt down a pre-made piece of steel rail | | | | carpet over the engine to help keep comfortable. |
| (to make up the height difference), and set the | | | | If you're comfortable you can almost always do a |
| new engine in place. | | | | better job. |
| Often two inches is the magic number. If you got | | | | Exhaust system |
| lucky and the new engine mounts sit exactly two | | | | The next step in the engine change is hooking up |
| inches high then buy a piece of two by four steel | | | | the exhaust system. Although this seems straight |
| extrusion 5mm or thicker. Lay the new rail right | | | | forward some thought should be put into the part |
| over the old engine beds, bolt them down, and | | | | of the project. If your new engine has a higher |
| set the new engine in place. Sometimes I have to | | | | horse power than the original engine its possible |
| take the extrusion to a shop and have it cut and | | | | the exhaust diameter will need to be enlarged. |
| welded to the special thickness I need. Either way | | | | Consider this project carefully. It can cost more in |
| make this particular, all important adapt-a-rail | | | | labor to enlarge the exhaust system than to |
| before you lift the old engine. | | | | change the engine. Tip-Often the exhaust manifold |
| Tip-While the old engine is out it is the perfect | | | | outlet on a new engine will be on the opposite |
| time to paint the engine area white, and maybe | | | | side as the original. If this is the case a simple |
| service the bilge hoses or anything else that runs | | | | solution to connect to make an S curve from |
| under the engine. Tip 2-Consider installing a series | | | | exhaust hose and two 45 degree elbows that |
| of lights that illuminate the engine from below. | | | | allows an easy, inexpensive connection to original |
| Your new engine is going to be very clean and | | | | system. |
| nothing helps keep an area clean like really good | | | | Engine panel |
| lighting. | | | | Most new engines come with a "plug and play" |
| Price saver | | | | wiring harnesses. In other words the wire loom |
| Often the DIY can save a bit of money by | | | | installation is simply a matter of pressing together |
| measuring, and doing the heavy lifting themselves. | | | | the supplied connections. Still, the wire loom should |
| Once this is complete call your mechanic to do | | | | be secured to the engine with wire ties to |
| the alignment and inspection. This can be a win | | | | prevent vibration. Where the wire loom passes |
| win for all. The local mechanic gets some of the | | | | from the vibrating engine to the rigid hull a loop of |
| work and catches the basic mistakes, while the | | | | extra cable should be left to take up the vibration. |
| owner pays to have the difficult part of the work | | | | The wire loom should be secured every eight |
| completed and yet does the easy work himself. | | | | inches along the complete rout to the engine |
| The Rest of the Fit | | | | panel. This may seem like a lot of securing points, |
| You will have to measure width, height, and depth | | | | but in years to come all new wires from the |
| of the new engine along with the motor mounts, | | | | panel to the engine will eventually follow the wire |
| but most modern engines are much smaller than | | | | loom possibly adding up to a large amount of |
| the twenty year old diesel you will be removing. | | | | wires. |
| The only time size has been a problem has is | | | | Preventing water backing up into the engine |
| when we remove a small engine and replace it | | | | The most common cause of damage to a marine |
| with a much larger model. The popular Perkins | | | | engine is salt water intrusion due to poor |
| 4-108 is now replaced by a Yanmar that is about | | | | installation of the water cooling hoses. |
| 2/3rds the size of the original. The 56hp Yanmar | | | | In order to reduce the chances of filling a new |
| is about the same size as Perkins 4-108 giving | | | | engine with salt water remember:o Put in an anti |
| almost half again the horsepower. | | | | siphon loop between the engine water outlet and |
| Lifting the Old Engine | | | | the exhaust elbow inleto This loop should be at |
| The lifting, and removal of the old engine is the | | | | least a meter above the outside water lineo The |
| next step of what some do it yourselfers may | | | | loop should be on center lineo The top of the loop |
| find overwhelming. I almost always lift from the | | | | should have anti siphon break, or better a anti |
| main boom supported by halyards. I attach a | | | | siphon loop that feeds a small hose that trickles |
| block and tackle to the lifting point and then run | | | | somewhere the operator can view, such as the |
| the bitter end to a winch. I use a land crane to | | | | cockpit floor. |
| set the engine on deck then take over myself | | | | Tip-Resist the urge to tee into the sink drain as a |
| with a boom lift. I always use two lifting points on | | | | place to "trickle" the anti siphon water. More than |
| every aspect of the lift. If any single line were to | | | | one new engine has been ruined when the sink |
| break the engine would not fall. The lifting lines are | | | | was plugged and filled with water to wash the |
| tailed to the two largest sheet winches on the | | | | dishes thus sealing the anti siphon loop. |
| boat. | | | | Remember, just because the engine did not flood |
| The crane lifts the engine onto the yacht's deck. | | | | for the first year does not mean the water |
| Unless you really trust your crane driver it's often | | | | system installation is correct. It may simply mean |
| better to move the engine by block and tackle | | | | the rubber impeller in the salt water pump is |
| the rest of way to the new engine beds where | | | | blocking the flow of seawater at rest. The day |
| the movement can be controlled with precision. | | | | may come when the impeller wears and allows |
| Lifting the engine using the boat's rig. Pay | | | | water to creep pass filling the exhaust system |
| particular attention to the gooseneck or | | | | and the engine with destructive seawater. |
| connection between the boom and the mainmast. | | | | Take one last look at your installation. Check for |
| As long as the boom is in center line with the | | | | loose bolts, leaks, drips, oil in the engine and |
| boat the load should be in compression, or pushing | | | | gearbox, and coolant in the heat exchanger. If all |
| into the mast. The problem can occur when we | | | | is ready then were ready to sea trial. Tip-On initial |
| attempt to swing the boom out to the side. The | | | | start up be sure to hold the stop lever and turn |
| load on the gooseneck turns from one of | | | | the engine with the starter till oil pressure builds. |
| compression to side load. Inspect the gooseneck | | | | This will lubricate the dry engine before the first |
| carefully and keep the load inline with the mast as | | | | start. |
| much as possible. | | | | Sea Trial |
| Throttle connections | | | | When you finish your installation it's time to test. |
| A common challenge with a new engine is a | | | | If this is indeed a new installation then the |
| reverse throttle action on the injection pump. At | | | | manufacturer representative should be on hand to |
| the helm push might become pull, or however you | | | | activate the warranty. Have the engine access |
| move your throttle control now may be reversed. | | | | open and be ready to observe the engine. Hold |
| We can choose to get used to his new throttle | | | | the stop button and turn the engine over for a |
| linkage, or we can build a throttle reversing | | | | few seconds. Did the oil pressure build? Did the |
| mechanism. This reversing mechanism should not | | | | engine sound smooth? If so start it up and let it |
| be taken lightly. Engine control systems must be | | | | idle. Check the engine control system and look for |
| 100% dependable. If the throttle linkage were to | | | | leaks. Follow the exhaust system to verify it all |
| fail during docking it could cause an expensive | | | | looks and feels right. Put it in gear at low rpm's. |
| accident. For this reason take your time and over | | | | Does the back of the gearbox make little circles |
| build all shifting/throttle linkages. Notice in the | | | | following the prop shaft? This is a sure sign of a |
| photo we used 4mm plate on the reversing | | | | misalignment, bent shaft or other drive train issue. |
| system and red Locktight on all bolts. | | | | Take the boat out for a test run. Will the engine |
| Occasionally it may pay to haul the vessel for the | | | | reach maximum rpm's while driving the boat? This |
| engine change, but this is only if other work needs | | | | verifies the prop is of the correct pitch. When run |
| to be performed, or if the prop and maybe shaft | | | | at higher rpm's does the engine shimmy and |
| are to be changed. Otherwise it's almost always | | | | shake or maybe pump for and aft? Not just |
| easier to do the engine change while the boat is | | | | vibration, but a cyclical motion that is not present |
| at the dock. | | | | when the engine is run at high rpm's in neutral? If |
| Tip: If you're lifting the engine on it's end then | | | | the engine sits smooth take one last alignment |
| consider slipping a plastic garbage bag right over | | | | reading at the coupling to verify your final reading. |