Repowering 1989 37' Egg Harbor from Gas to Yanmar Diesel

By: criscarlin@comcast.net

I have just completed a repower project on an 1989 Convertible from gas to diesel and thought the readers might find interesting. First step was to remove the engines and degrease and paint the engine room after removing 5 gallons of antifreeze from each engine bay. The new Yanmar engines and ZF gears were used as a template for new forward engine mounts as the rear mounts lined up.Once these were lined up to the old shafts we were able to pull the struts and send them for machining to accept the new 1 3/4 shafts. New gauges were ordered as well as shaft logs, packing glands and props. The raw water intakes had to be enlarged and  moved forward about two inches to clear the engines and accomodate more flow. As it turns out the intermediate strut was removed once before I owned the boat and a bolt was broken off in the hull, who ever reinstalled it just put the bolt in next to the broken one and caused binding of the shaft. We were able to spac e the strut aft to eliminate the binding and fix the bolt hole after getting it out. The end result is awesome to say the least. The boat now runs smooth as silk with no hesitation or vibration. Cruise went from 14 knots at 3400? rpm to 24 knots at 3000 rpm. WOT was 18 knots and is now 27.8 knots at 3400. Fuel consumption is still unknown with only 20 hours on the new engines, but at cruise I was getting about 150 miles to a tank (400 gallons) in ten hours. On the ride hime varying rpm I went 125 miles and used less than 1/2 tank in 5 1/2 hours.  I am confident that these numbers will be repeatable once the engines are broken in completely. We also added a 8k Maspower genset that uses a three cylinder Yanmar engine and a Northern Lights rear end and an oil x-changer system for both motors and genset. The fuel tanks were pumped cleaned and reused after adding larger fuel lines and  return lines and Racor filters. We were able to reuse the exhaust f or the engines but had to enlarge the genset exhaust. Air intakes in the engine room were sufficient and needed no modification.  The new props are 4 blade 26 x 28 with no cup and allow me to reach 3500 rpm full fuel and water.The boat could probably use larger rudders but will work fine for now. Harbor handling is crisp with the larger props and speed is 4.4 knots at idle. I am very pleased with the outcome of the repower and would reccomend it for anyone with a 1989 convertible. I was amazed by how easily the boat converted to diesel,it was really thought out from the beginning(probably designed for diesel) as it needed it as the boat is very heavy for gas engines in my opinion. I am still glad we bought an Egg Harbor as now it might just outlast me!