Completed Repower of 38 ft Commander

[pwrobert]

Just completed the repower of my 1965 38ft Flybridge with rebuilt 6BTA 370’s with new ZF220A’s 1.75:1 Had Tony and guys build up a new exhaust system and fitted some of the SB engine upgrades and new custom engine and transmission mounts.

With the old Detroit 8.2L Turbos with 2:1 TD 502’s top end at 3000 was 25 mph with cruise at 18 – 21 mph depending on load. Cruise at 2600 RPM burned 18 G/H. Propped with 3 blade bronze 22X20 on 1.5” shafts. Carries 300 gallons fuel and 80 gal water.

New setup uses 4 blade 22 X 20 Nibral’s with number 2 cup. Tachs out at 3150 now after repropping from initially trying 22×22 as suggested by prop shop. Top end is now 30+ mph and now cruises at 20-21 mph burning 17 G/H at 2250 RPM loaded for the Bahamas.

Finishing up the installation now of Maretron FFM100 fuel flow system and will be able to provide more detailed fuel usage at other RPM settings.

Topic

[pwrobert]

Reopwer Data and pictures

I think if you search on my name these should show up. I posted quite a bit in the past 2 years about this boat. fair number of pictures.

Essentially, I cleaned out the previous engines and rebuilt the engine beds. Painted and updated the engine room and all hoses- etc. Made a wooden jig to rough align the engine mounts before install. Set the engines.
Tony designed and made the engine mounts and designed and fabricated the entire exhaust from flange to prior mufflers. Sweet.

I did have to reset the struts for proper alignment. While at it I did a list of other upgrades/installs/repairs that turned out to be 30-35 lines long on a sheet of paper. Boat was on the hard from October until April getting the process done.

[Darren Kinvig]

6 bta repower.

Wow. I would sure like to ask you some questions. I am doing the same thing to a 28′ flybridge Single diesel tho. I’ve done fiberglass work, painting, and lots of stern drive installations. Never a inboard – V drive set up. Going from a Cat. 3208 borg warner to a 6bta Cummins with a ZF combination. If you have some pictures of what you did it would be great if you could post some. Sounds like it was well worth your time and effort.

[Bill Desmarais]

curious if you monitor your 370’s EGTs ??
Nice numbers !

[pwrobert]

Sea trial setup

Boat was setup with minimal instruments. Tachometers that we’re well calibrated, digital engine water temp and oil pressure gauges. GPS for speed trials.
I had a second person with me in the engine room wearing ear muffs watching the new PSS shaft seals to adjust the water so they did not spray at top speed. And just generally keep an eye on things while I ran things from the bridge. We did speed and tach settings to get an idea about the new props. Ended up taking 2” out of the pitch as it was a little over propped.
Boat now has SMX water pumps, SMX 160 thermostats, SMX fuel filters and I took off the fuel coolers. Replaced the K&N filters with those from Seaboard. Oh yea has a exhaust warning buzzer but no gauge.

[pwrobert]

Happy to give any info I have

You have to help me – not familiar with PID.

[pwrobert]

Better Table Formatting

Sorry the data spacing got all mashed together when the spaces between columns were compressed. Attached is a more readable table.

[pwrobert]

Additional Info about Repower Project

I planned to post these details last year after the repower job was completed but was held up by troubles (lightening strike taking out all electronics and more) and especially with getting the Maretron FFM 100 feul analyzing system and it’s sensors fully working. The Port installation of the FFM “brains” and the 2 MAR sensors went perfectly. Worked at first go. However the starboard has been a trial…I’ve been through 6 sensors and three FFM units to get any semblance of the Starboard working. Any way it works enough to allow me to report the engine data for these 6BTA 370’s.
The two engines are pretty well matched so I am reporting one set of data that is the same for both. The data is on the boat after 6 months being back in the water when the running gear painted with PropSpeed and bottom touched up. So Not perfectly clean down here in South Florida now but figures are real life.

RPM Speed in MPH G/H per engine Boost Engine Temp with SMX 160 thermostats
800 7.2 0.4 0 154
1000 7.8 0.7 0 154
1300 9.4 1.8 0 159
1500 10.2 3.0 0 159
1800 11.4 5.2 2 160
2000 15.4 6.3 4 160
2200 18.7 7.5 5 162
2300 20.5 8.2 7 163
2400 22.3 9.2 9 163
2500 23.5 10.3 10 164
2600 24.5 11.3 12 164
2700 26.0 12.3 15 165
2800 27.0 13.4 16 165
2900 28.0 16.9 20 165
3000 29.5 18.8 24 165

When the boat was first launched and after the props repitched to 22X 20 4 – Blade Nibrals Z220A 1:1.75 the boat did 31 mph at 3150 so these numbers reflect the effect of the slight bottom growth (slime probably but mild).

With the 180 degree thermostats the engines ran at about 175 degrees at normal cruise when our water temps are in the upper 80’s (gets over 90 on the Bahama banks sometimes)..

Overall the Total fuel and calculations with the GPS data shows it running at 1.1 to 1.2 Miles/Ga when in the 2200-2400 RPM Range according to the Maretron units.

[pwrobert]

Update 2020

Well last year I had the boat out for the repower job I mentioned above. Redid some basic fiberglass work along the way and had a nice trip to the Bahamas. Engines and boat performed wonderfully – loaded for the trip – full fuel – gear – freezer stocked boat uses now 1 Gallon per hour less at a cruise of 1 to 2 mph over what I got with the takeouts.
This past winter I had the boat out for my “final” big job of getting the 55 year old girl painted top to bottom (did the entire bottom last year). Flybridge, Cabin tops, Decks and Hull all got their Awlgrip replaced. With the addition of the inside headliners all around this is the best the boat has looked since coming off the showroom floor.
All this work has been done in prep for my retirement with the plans to use it more heavily. The boat is ready but COVID has put a monkey wrench to the exit dates a couple of times but should soon get that sorted out and get back on the water.

BTW the fuel line purging system I last posted about seems to work pretty well and allows me to fill empty fuel filters and purge spill free. Now if I can just get away before the storm season kicks up.

[PHILIP H EASTMAN]

6BTA Repower

Just repowered with same 6BTAs. is there a checklist, PID or similar instrument that was used when you repowered. getting ready for a seatrial and would like to know in advance what the specs are. thanks.

[Tony Athens]

38ft Commander repower

Getting better than 1:1 on plane in a boat that size tells me “ya done all 100% right”……………. Good job…. Post some install pics to helps other..

Also, and super important to stress is that letting these types of engines spin up, and spin-up easily to 100-150 RPM above their minimum rated speed…………… Why typical props shops seem to have a such a hard time understanding this is beyond me.

Tony

[Author]

Replies