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Looking at hull that previously had CAT 3126 w/shaft. What would be most commonly available diesel repower options, specifically Detroit Diesel and Volvo Penta.....in 350hp range. Thanks for your help and advice
Why not replace with C9's, qsb's or yanmars ? I personally can't stand volvo because of cost <-- just opinion. I love detroits but they are HEAVY. You should talk to GregDPM, also post about the exact hull make and year
Hull is 30ft Island Hopper with 12ft beam. Straight shaft / rudder combo. I have good Volvo mechanic, thats why I agree with cost for the most part, but if properly used / maintained, Volvos will outlast anything out there....at least ones I have owned in 130-200hp range have been flawless. Now this hull needs more power, and I gotta look into more costly options in both Volvo and Yanmar/Detriot/etc. What is QSB?
Hull is 30ft Island Hopper with 12ft beam. Straight shaft / rudder combo. I have good Volvo mechanic, thats why I agree with cost for the most part, but if properly used / maintained, Volvos will outlast anything out there....at least ones I have owned in 130-200hp range have been flawless. Now this hull needs more power, and I gotta look into more costly options in both Volvo and Yanmar/Detriot/etc. What is QSB?
looking on yacht world, comparing a couple, there was no real difference in speed from the 300hp 3126 to the 440hp yanmar. Which results in your hulls design.
Why would anyone look to replace a 3126 with a Detriot Diesel or Volvo?
Detroits are just old technology, and Volvo's are way overpriced.
For a value purchase, Cummins B370 remans - they are 355 hp and can be had for less than $20k with a full Cummins warranty. They will also bolt right up to your reduction gear.
If not on a budget, CAT C-7's (460 hp) or Cummins QSB's (380, 425, 440 or 480 hp) are all good choices, but will be in the $30-40k range.
Thanks for the suggestions. After buying the hull, I am on a tight budget. I have used RTO 8V71 turbo intercooled Detroit Diesel locally for $3500 (should be around 400hp), so I was thinking along those lines. As long as it makes the power, and is reasonably easy to maintain, it would work for me. I can't afford $20,000 motor
stringer have you weighed an 8V71 lately? I am thinking about 2500 pounds before tranny. What tranny are you looking at and old Allison? Power rating is 1064 ft·lbf @ 1200 rpm 305-370 hp governed at 1800-2100 rpm (turbocharged/aftercooled). You could get it done; but the weight and low output are problems. Plus they really sling oil usually.
I think a 3126 is around 1600 pounds plus a 3126 tranny is light compared to and old allison. You might want to load 3000 pounds of water in the engine compartment and see where she sits. That is about 365 gallons or 6.5 55 gallon drums.
Maybe you can find a good RTO cummins or Cat. I understand that will not get you to $3500 though.
8v71 is damn near twice as wide as your 3126, you really have to build up thoose stringers and move you mounts, whats wrong with the 3126 ? You probably also dont have the clearance for a prop big enough for that 8-71 to use, therefore you will be much slower. You can try and get away with a 1:1 trans to make up for it and spin a 4 blade with more pitch but you might wind up cruising 6-8 knts @ idle and will most likely want to install a trolling valve.
Thank you for great info. I have not seen 3126 in person, so i presumed it was about the same size to 8v71t, due to similar output. I will look around for something else
Thank you for great info. I have not seen 3126 in person, so i presumed it was about the same size to 8v71t, due to similar output. I will look around for something else
A 3126 is about 4" longer and 2" wider and 3" higher than a 5.9 Cummins (like in a Dodge Ram pickup). It weighs 1,550 lbs, and with a ZF gear, about 1,700 lb; an 8-71 is 3,100 lbs, 3,400 or so with the gear.
My guess is an 8-71 won't fit.
Save the $$ for a while and find yourself a Cummins B series. We repowere our 35' express in the late '90s with 2 370Bs. they replaced Volvo TAMD70E. We lightened the boat by over 2K lbs and ADDED 110 hp, it was like a new boat.
The engines were bulletproof. they were propped to turn up 3k RPM (recommended) with a full canyon load. We cruised them at 2350 (we found that as the sweet spot for our boat) and were getting 22-24 knots burning 20 gallons an hour. when we wanted to (and when conditions allowed) we could cruise em all the way up 2800 RPM - and run them there all day - for an honest 28 knots. not bad for a 24,000 lb. boat. We sold the boat with 1200 hours on them and never did anything other than regular scheduled maintenance.
My point (after the long winded story - sorry) is that a diesel re-power is a big undertaking and a lot of things crop up and you WILL go over budget! Save the $$ and scour the internet and yards, and find that used B-series. Do it once and do it right - even if it means missing some time on the water.
Looking at hull that previously had CAT 3126 w/shaft. What would be most commonly available diesel repower options, specifically Detroit Diesel and Volvo Penta.....in 350hp range. Thanks for your help and advice
D6 volvo 350 is on Ebay right now $18,000 low hours. 2 available.
CAT 3126 repower options.... 
I agree with cost for the most part, but if properly used / maintained, Volvos will outlast anything out there....at least ones I have owned in 130-200hp range have been flawless. Now this hull needs more power, and I gotta look into more costly options in both Volvo and Yanmar/Detriot/etc. What is QSB? 
