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As started elsewhere this is the summary of a repower of my 36′ Northern Bay Downeast boat from a damaged QSM 11/670 to a reman QSM/670 . What seemed to at first be a simple plug and play turned into a seemingly endless series of one by one steps. What was expected to be a 2 week out and in process turned into an almost 2 month affair.
Basics – Skipjack is a 36′ Northern Bay – classic Maine downeast hull. Fully loaded she is somewhere in the 21-22,000 pound range. She holds 300 gallons of fuel (not the 330 advertised when I bought her) and 20 gallons of water. I use her most often for local cruising and bottom fishing with wife and friends on 20-40 mile/20-40 gallon 3-5 hour trips. However I also use her 25 times/year for offshore trips ranging from 50-120 mile short out burning 100-240 gallons of fuel. Those offshore trips range from 10-48 hours in length, carry myself and 4-5 guys, 500-750# of ice and load the boat and engine to the gills.
MY old QSM 11/670 was paired with an ancient and twice rebuilt IRM 310 1.54:1 gear couple to a 11′ 2.25″ shaft and driven by a 26 x 24″ Michigan Wheel DQX prop.
The old QSM had 2600 hours on it when I ingested water into my fuel and had a chequered history. The Echaust manifold had leaked 4 years ago at 550 hours and th aftercooler and heat exchanger had extensive corrosion.
After an expensive rebuild I cut the original 26 x 26 prop to first 26 x 25, then 26 x 24 to try and lose load and exhaust gas temperature at my normal 1850 RPM cruise.
The 26 square prop pushed the boat at close to 21 knots at 1850 RPM burning between 19 and 20 GPH, 26 x 24 pushed it at 19 knots, just under 18 GPH st that same 1850 RPM. At canyon load my EGT was always 1050-1075, would and did creep to 1100 in warm 76 degree plus water. 2000 hours of watching a pyrometer gauge taught me EGT peaked between 1600 and 1800 RPM, dropped down 25 degrees between 1800 and 1900 RPM and dropped another smaller increment between 1900 and 2000 RPM.
as I wrote in the QSM rebirth thread, due to the profile of my boat and trips – single engine, 120 mike offshore I opted to purchase a reman engine versus rebuild the existing one.
the way I looked at it, the cost of transport to place of repair was equivalent, haul and launch was equivalent, engine removal and re installation was equivalent while cost of rebuild vs reman was the only significant difference.
i also knew I had “overhang”, ie pending repair or replacement on the old exhaust manifold, the old aftercooler, the old exhaust elbow and the old turbo as well as the old vessel view screen in my mid to near term future. Those pending future expenses helped make the reman decision easier.
I will pick up in the next post with the start of the repower project.
My timeline was as follows:
8/19 – engine declared unusable
8/20 – reman decision made
8/25 – reman QSM located
~9/3 – repower plan and location determined
9/9. – 75 mile tow by Seatow to repair Marina
9/13 – boat hauled
9/16 – old engine out
9/17 – old gear declared bad, new gear decision made
9/22 – new engine on site and dressed in shop
~10/1 new gear in shop
10/4 – new harness pulled, new vessel view put in console and wired up
10/5 -engine and gear lifted into boat – discovery of need for new shaft coupling (10 vs 8 bolts) and new gear leg geometry.
10/6 – engine connected to boat and remove doarts bolted back on, coupling sourced and loosely installed for fit
10/13 – new gear legs in, fit is wrong, back for refabrication
10/20 – new gear legs and mounts finally fit ( multiple tries) – engine and gear bolted down and loosely aligned. Shaft coupling connected
10/24 – shifter bracket and cables installed and connected, engine control powered up (electric wiring surprises found)
10/26 – wiring completed, boat splashed, final algnement, engine started at dock.
10/28 – initial sea trial and WOT run in 25 knot conditions
10/30 – quick sea trial and test, 75 mile careful run home.
11/2 – retorque all bolts, address small punch list, do formal sea trial and register engine as “on” with Cummins.
pictures of boat, the old engine/valve cover off and empty engine room…
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