Replacing the Diesel Engine - SailNet Community
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Replacing the Diesel Engine

Out with the old. The time had come to remove the green beast and the "engine room spaghetti", resolving the engine-confidence issue once and for all.
It wasn't a pretty sight! "Engine room spaghetti", we had soon dubbed it. Twenty two years of multiple owners patching and mending, each who had added their own unique flavor in the keep that engine running department.

"Cross your fingers!" We'd say to each other every time we fired her up. Sometimes it took a little coaxing to bring her to life. It wasn't that we'd experienced problems yet, we simply had no confidence in the way the engine and its systems were set up. Rust ran rampant and suspect hoses seemed to multiply overnight. Recently Larry confided in me that he used to wake up in the middle of the night, in a cold sweat, and secretly check the engine room with a flashlight to see if any of the old systems had failed or sprung a leak while we slept—a condition not especially conducive to a peaceful night's sleep. We knew we couldn't cruise comfortably always expecting our engine to quit at any time.

We were faced with several options:
  1. Leave everything as it was and just continue patching old, suspect systems.
  2. Have the old engine removed and rebuilt, while rejuvenating the engine compartment systems.
  3. Install a new engine, with transmission, and replace all systems.

Preparing to remove the old engine brought some sights not normally seen underway.
Leaving everything as it was and simply patching was not acceptable—plus, Larry was losing too much sleep. We seriously considered having the old engine rebuilt. Diesel engines last forever, right? Well—maybe. The prices we were hearing for rebuild jobs ranged from $2,000 to $7,000. The more we talked with other cruisers, the more horror stories we heard concerning rebuilt engines. Every single person we met who had an engine rebuilt experienced further problems after the rebuild was completed. One couple we know has now spent over $11,000 on their 15-year-old diesel!

We studied our options and prices. Finally we agreed to bite the bullet and invest in a new engine and all new systems for the engine room. In all honesty, this was our pre-disposition from the start, and we had budgeted for a new engine with our original decision to buy Serengeti. Also, after cruising about for awhile, we felt she was under- powered.

Knowing what to leave to the pros and what you can do yourself is one of the central keys to boating happiness. Here a template for the engine is put into place to design mounts for the process of alligning the engine.
With the decision made to install a new engine, we then had to decide what make and horsepower to consider. In our poll of marine mechanics, cruisers, boat brokers, and others in the industry, one brand came up most often—Yanmar. We were hearing good things about Yanmar from cruisers as the best bet for parts and service anywhere you went. When we later got our new owner's manual and found it printed in 14 languages, we were further inclined to believe these reports.

We measured our engine room and determined that space was not going to be a problem. Today's engines are smaller and lighter than yesterday's brethren. So, what horse power to buy? Our boat had an old Volvo 75 hp, but we knew that our type of boat was built in later years with an 85 hp engine, and felt that was probably close to what we needed. The closest engine to fit our needs that Yanmar offers was a 100 hp model. A little more than we had thought we'd install, but after consulting with some engine mechanics, it was determined that it shouldn't be too much for our 46-foot boat of 33,000 lbs displacement. Surprisingly, the 100 hp was only a few hundred dollars more, and no larger or heavier, than the next model down in size, a 75 hp.

Having the engine out is an opportunity to finally get the engine room spiffy, complete with sound insulation.
The next major decision was who would install it. As has become the norm with Serengeti, Larry wanted to do it himself, but in this case didn't feel he had enough experience to get the engine properly bedded and aligned. The goal then became to find someone with whom Larry could work, doing most of the work himself so as to really learn about the engine, having a professional do the engine bed and shaft alignment. After searching around, we finally found a Yanmar mechanic who worked on his own and who was perfect for the job.

Hauling out at the boat yard and preparing for our new engine was very exciting. As soon as we were propped up with jack stands, I began removing the caulking from around the cockpit floor, while Larry was below disconnecting the steering cables. When it came to the physical act of removing and replacing an engine, we were one of the lucky boats—our entire cockpit floor is removable, and the engine sits directly below. In an hour or so we had a rope around the pedestal, winching the whole cockpit floor up in the air using the main halyard while Larry guided its path. He looked funny holding that beautiful wooden steering wheel way up in the air!

Mounts in place awaiting the new iron genny.
It took Larry about half a day to unbolt and disconnect all the lines to Serengeti's old engine. We discovered, due to our relatively deep draft (6'-6"), that the boatyard's fork lift would not reach high enough to remove the engine, so a crane was called in to do the honors. The crane quickly and easily plucked the old engine out and we were left with a gaping hole in the middle of our boat—a big, oily, smelly hole. We dove in, cleaning, scrubbing, wiping, and scouring until all traces of grunge were gone. We decided to apply a two-part epoxy paint to the engine room floor. This would provide an impenetrable surface that should last for many years. And best of all, no more "eau de old diesel" smell down below.

Next our engine mechanic, Charlie, showed up with a wooden template that he had built from the actual new engine. With this in hand, he was able to confirm the fit of the engine to our space, and design engine mounts that could be bolted in the correct spot before the new engine was lowered into place.

Easy does it. The newest member of the family is lowered onto its mounts.
After the position of the engine had been confirmed by the template, we were able to move forward with other important issues. As expected, our existing shaft was not long enough due to the newer, more compact engine and transmission. Knowing a new 10- foot long, inch-and-a-half diameter shaft was going to set us back over $1,000, we were thrilled when one of the boat yard guys said, "Hey, I think there's an inch-and-a-half shaft sitting over there in the work shop. It came out of a trawler that ran aground a few years back." Sure enough, there was a 13-foot stainless steel shaft, bent just at the very end, and perfect for us to have cut down and reconditioned.

While Charlie was fabricating the engine mounts, we had our hands full. First, we removed the old shaft and cutless bearing—actually bearings in our case, as there was a second cutless bearing immediately aft of the stuffing box. Our more powerful engine required a larger diameter water intake and exhaust hose. Larger diameter hoses meant new mufflers and fittings for the exhaust, and a new strainer for the salt water intake. After these, our next priority was to have all engine room systems logically arranged, easy to reach and able to be quickly evaluated. No more engine room spaghetti for us.

Larry installed a new fuel supply and fuel return manifold, reconditioned our primary fuel strainers, and added new fuel lines, which was only appropriate for the two new fuel tanks installed earlier. Next, while he could still easily move about in the engineless room, he laid out our bilge pumps and all associated plumbing. Having found that the small strainers commonly found on bilge pumps clog easily, we replaced the old ones with much larger strainers.

Two-inch thick convoluted foam sound insulation was glued and mechanically fastened to the empty engine compartment, and new engine room lights were installed to allow for easier maintenance and evaluation. Now, ready for the new engine, we gave Charlie the mechanic a call.

After the new engine bed was bolted on the stringers and the new shaft was put in place, we watched the crane lift our shiny new engine high into the air. I hardly had time to get the lens cap off the camera to snap a shot before it settled perfectly into place.

Ta-Da! That wasn't so bad. The final product.
Charlie installed the flexible coupling, designed to absorb shock loads and reduce vibration to the shaft, and aligned the engine. When the final bolt was turned on the engine mounts, Larry enthusiastically jumped back in (every day in the boat yard costs money) and began hooking up the exhaust, fuel, and water hoses. Since the water injection point of our exhaust system is below the water line, he also installed a siphon break in the cooling water discharge hose which is recommended to prevent cooling water from siphoning back into the engine when it's turned off.

We were amazed to find the engine surprisingly easy to wire. The entire electrical harness consisted of four plugs that connect the control panel to the engine. A black, negative battery cable to the engine block and a red, positive one to the starter completed the entire electrical hook-up.

All we had to do now was hoist that cockpit floor back high up in the air and seal it in place, connect our shift and throttle cables to the new control lever, and hook up the steering. We were ready to go back in the water!

A test run reveals all systems functioning properly.
It was with great anticipation that we turned the ignition key for the first time. As hoped for, there was no big roar, loud rumbling or billowing black smoke. Our new engine expressed itself with a gentle purr, just like you'd expect to hear from a young lion cub.

So, how difficult was it to do most of the new engine installation ourselves? Surprisingly, it was not so bad. The whole process took us 14 long, hard days—we're talking 10-12 hours—but as a result, we both know considerably more about diesel engines than we ever thought possible. In fact, we're now familiar with the turn of almost every screw used in the installation and feel much more qualified to maintain the engine and diagnose any problems. In addition to our new knowledge, we estimate we saved in the neighborhood of $4,000 to $5,000 over a turn-key installation. Not bad for two weeks of work!

Cost and Considerations for Choosing a New Engine

Important Considerations When Choosing a New Engine

Following are questions you will need to answer before you begin the process of re-powering. Some you can figure out for yourself, others may require the assistance of a mechanic.

 What horsepower engine do you need? What power fits your boat's need and what size physically fits your engine room?
 What make and model is right for you? Check on service and availability of parts.
 Does the engine you're considering have an operational side and a non-operational side designation? The operational side contains the fuel filter, oil filters, dip stick, etc.—most of the items to which you need easy access. Make sure that space allows easy access to the operational side of the engine. If it doesn't, you may need to look at a different manufacturer and/or model.
 Will you need to modify your engine bed or stringers?
 Can you use your existing exhaust system, fuel hoses, and water intake hoses? Are they adequately sized?
 Will you have to modify your prop and/or your shaft? What direction does your current prop spin? Left hand or right hand? Is it compatible with a potential new transmission and engine size?
 Do you want to install a flexible coupling?
 Is your engine room sound insulation adequate?
 Will you need to haul out of the water for your new installation, or can it be done dockside?

Cost of Installing a New Diesel Engine

If you're thinking about re-powering, the following is a summary that may help you. These were our costs (May 2000) in making the switch from an old engine to new. Keep in mind, we replaced virtually everything in the engine room, and all labor was supplied by us, except where noted *. As ours is a 46-foot center-cockpit boat, with the engine located in the middle of the boat, there are longer runs of exhaust hose and shaft to consider than in a typical aft cockpit boat.

Don't let anyone tell you your old engine is not worth anything without further investigation. One mechanic told us ours was basically worth nothing. Nobody wanted to deal with old engines. A few days later we sold it easily, along with the transmission, to another cruiser (who had it checked out by a mechanic before buying it), and got $1,600! In fact, once we let it be known it was for sale, there was a lot of interest.

Labor and Supplies Cost
Engine and Transmission Yanmar 4JH3 100 hp


FL tax $868
Freight $275

Total $12,721

Mechanic's Labor Install and align engine $800
Angle Aluminum Engine Brackets $75
Shaft Used/reconditioned 1-1/2-inch x 10-feet $480
Cutless Bearing 1-1/2-inch $100
Flexible Coupling R&D brand (PYI) $150
Exhaust Hose 3-inch x 21-foot wire reinforced $273
2 - 45 degree Exhaust elbows Trident Rubber $82
2 - 90 degree Exhaust elbows Trident Rubber $85
Transom Exhaust fitting   $38
10 - T-clamps   $90
Fiberglass Exhaust Pipe 12-inch $10
Water Lift Muffler & Gooseneck Vetus $200
Seacock & Thru- hull for engine intake 1-1/4-inch Forespar Marelon $70
Engine strainer 1-1/4-inch Groco $100
Siphon break Vetus $43
Fuel lines 5/16-inch x 30 ft $52
Epoxy paint Interlux 2000 $50
Sound-proofing 2-inch convoluted foam $280
adhesive for above (8 sheets .27-inch x 54-inch ea) $50
Battery cable 2-0, tinned, 23-feet $115
Dripless Stuffing Box Replacement lip seals $40
Lights & wiring for engine room   $30
Fuel Manifold Supply & return $35
Engine intake hose Raw water supply $25
Stainless Hose-clamps Good ones—solid band with stainless screw assembly. Two on end of each hose. $80
2 Control cables Morse 33C - 7-feet $62
Coolant   $20
Engine Oil   $21
Transmission Fluid   $5
Crane Rental Remove old engine $100
Crane Rental Set in new engine 2 weeks later $100

Grand Total $16,382


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