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Thread: Looking to Boorrow Volvo B2 Duoprops . . .

  1. #1

    Default Looking to Boorrow Volvo B2 Duoprops . . .

    Thinking that I need to downsize my duoprops but want to try a set of smaller props before taking the plunge.

    If anyone has a set of Volvo B2 and/or B1 duoprops that they would be willing to lend please let me know.

    Appropriate compensation would be in the form of beer, wine, gas, $ or whatever . . .

    Thanks in advance.

    Please email me directly to stroganof@gmail.com or call cell at 727.2180.

  2. #2
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    what are you running now and what is happening with them? post some numbers on here so we can help.

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  3. #3

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    Running B3s now on KAD42 engine but have added weight to boat (bigger tank, bigger winch, fancy pot puller, rear canopy, larger children & more gear) and it is struggling to get on step and doesn't reach full rpm. It was fine (well, more like adequate) prior to added weight, but now with full fuel and loaded it is a bit piggish and barely crawls onto step. Once on step it is okay, other than WOT rpms are low. Went from 10,000lbs to close to 11,000 (guestimate). Thx.

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    I had A's on my 41P volvo and i thought the diesels were supposed to run A's. OK so my bowpicker i ran a set of C4's stainless props, if i remember correctly they were both 3 blade, boat weighted aprox 9500 w/100gals fuel & i got 3950 WOT. I originally ran A4's that were ok then tried A5's that gave me more speed but with a load of fish my pyro temps would get to hot so thats when i went with the SS C4's, one less blade for the set and i got good performance with and without a load on the boat & pyro temps stayed at aprox 775 at cruise and 850 w/load.
    Are the B's 3&3 blades or 3&4 blades. What reduction is your drive ?? mine was 1.96:1. Rule of thumb is you'll lose/gain 200rpm for each size move. What were you getting for WOT before the added weight and what are you getting now with the weight added. What did you run for rpm's for cruise ?? I'm betting with the load you are putting on the engine now your exhaust temp is really hot, those engines don't like to be run hot or to be overheated, they don't last very long then and those 42's had a history of blowing up(bad pistons) in the cordova gillnet fleet, i think just about every one installed over there blew up and some more than once.
    It might take more than just a prop change to fix your problem and maybe your engine just doesn't have enough balls to push that much weight no matter what you do. Post some more numbers and we'll see what we can come up with.

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  5. #5

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    Thanks Steve. Was getting 3800 WOT prior, did not check it last trip out but will do so next time out and post.

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    Have you checked all the simple stuff already, fuel lines, filter sucking air/leaks,turbo fins for play, air filter, control cables the simple list goes on. Don't they want that engine to turn 3900 WOT ??

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  7. #7

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    Steve - have not checked turbo or controls, but am certain that fuel and air are not the issues (new filters etc). Got a little focused on excess weight being the issue so the reminder to check basics first is a good one. Will eliminate what I can this weekend and see what turns up. Thx.

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    Quote Originally Posted by potbuilder View Post
    I had A's on my 41P volvo and i thought the diesels were supposed to run A's. OK so my bowpicker i ran a set of C4's stainless props, if i remember correctly they were both 3 blade, boat weighted aprox 9500 w/100gals fuel & i got 3950 WOT. I originally ran A4's that were ok then tried A5's that gave me more speed but with a load of fish my pyro temps would get to hot so thats when i went with the SS C4's, one less blade for the set and i got good performance with and without a load on the boat & pyro temps stayed at aprox 775 at cruise and 850 w/load.
    Are the B's 3&3 blades or 3&4 blades. What reduction is your drive ?? mine was 1.96:1. Rule of thumb is you'll lose/gain 200rpm for each size move. What were you getting for WOT before the added weight and what are you getting now with the weight added. What did you run for rpm's for cruise ?? I'm betting with the load you are putting on the engine now your exhaust temp is really hot, those engines don't like to be run hot or to be overheated, they don't last very long then and those 42's had a history of blowing up(bad pistons) in the cordova gillnet fleet, i think just about every one installed over there blew up and some more than once.
    It might take more than just a prop change to fix your problem and maybe your engine just doesn't have enough balls to push that much weight no matter what you do. Post some more numbers and we'll see what we can come up with.
    I blew mine up twice in less than 1200 hours. Each time it got rebuilt they would de-tune it. 3 different styles of pistons and 3 timing changes later it held together. Started with B4 and could only turn B2 when I got rid of it. I imagine it lost 30-40hp from stock. Never had outdrive issues as we never trolled on it, plus the engine wouldn't run long enough to wear one out anyway. Pulled it and put on twin 200 Yamahas. No more reliability issues after that but the fuel burn sure increased.

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    11,000 hours on my duoprop drive, went through 2 41's with it but i still would not ever own another outdrive or volvo product.

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  10. #10

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    Finally got to the bottom of the issue – the tach (replaced last year) was reading very low and the weight was lugging the engine. Thanks to a $20 non-contact tachometer from Amazon it was possible to confirm that the WOT rpms are 3,770 and that cruise rpms were at 3500 (I had been cruising at the usual speed per GPS), pretty much per spec. Running with ¾ fuel and with less personal gear got rid of the agonizing push to get on step. Lessons learned – calibrate the tach and watch the weight. Planning to go one step down slightly on the prop size (B3 to C2) and go with stainless which should increase WOT to 3,900 or so and give a slightly more oomph in the mid-range for those trips when the boat is loaded for longer trips. Thanks for the tips everone, especially the “back to basics” suggestion from Steve. Since I am neither an ace mechanic, nor a salty dog, those suggestions are particularly helpful.

  11. #11
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    Quote Originally Posted by stroganof View Post
    Finally got to the bottom of the issue – the tach (replaced last year) was reading very low and the weight was lugging the engine. Thanks to a $20 non-contact tachometer from Amazon it was possible to confirm that the WOT rpms are 3,770 and that cruise rpms were at 3500 (I had been cruising at the usual speed per GPS), pretty much per spec. Running with ¾ fuel and with less personal gear got rid of the agonizing push to get on step. Lessons learned – calibrate the tach and watch the weight. Planning to go one step down slightly on the prop size (B3 to C2) and go with stainless which should increase WOT to 3,900 or so and give a slightly more oomph in the mid-range for those trips when the boat is loaded for longer trips. Thanks for the tips everone, especially the “back to basics” suggestion from Steve. Since I am neither an ace mechanic, nor a salty dog, those suggestions are particularly helpful.

    if you are cruising at 3500rpms i'd expect a trip to the rebuild shop soon.

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  12. #12

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    Why is that Steve? Volvo says the engine is designed to be operated at 200rpm below WOT.

    Perhaps prudent to run a little slower, but it is hard to imagine that running at spec will cause need for rebuild anytime soon.

    What am I missing?

  13. #13
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    Quote Originally Posted by stroganof View Post
    Why is that Steve? Volvo says the engine is designed to be operated at 200rpm below WOT.

    Perhaps prudent to run a little slower, but it is hard to imagine that running at spec will cause need for rebuild anytime soon.

    What am I missing?
    What your missing is vovlo wants you to run them hard so they get to sell you lots of EXPENSIVE rebuild parts or maybe another wonderful engine they make. Ask Volvo how many hours they expect you to get running 200 under ? Put a pyrometer on that engine and see what your running for exhaust temp at those speeds, i'll bet you'll see over 1100 degrees(or more) so your basically at melt down temps. The guys in cordova used to feel very lucky to get 3000 hours( many got less than 2000) out of their 41's, same thing they were melting them from the inside out with high exhaust temps when trying to get on step with extra weight(fish) on the boats. Your doing the same thing but instead of fish your doing it with people, gear, ice. Weight is weight. Those engines are pretty much gutless when trying to push anything more than a skiff and the small exhaust passages don't do anything to get rid of heat/backpressure. I spent 5 seasons trying to get my 1st 41 to run right and it never happened, replaced it with a 41P and it was a little better but still pretty much gutless but i learned how to run it and not blow it up by keeping the rpms down, never cruised it over 3350, WOT was 3950, and when i had fish on the boat i pretty much ran it by pyro temps(never over 900) my cruise temp was 775-800. The next weakest link is the pos duoprop drive can't take the strain/weight either and when loaded i could hear the difference in the sound(growling) the drive made, so if the engine didn't melt down the drive usually blows up sooner or later. Go on "boatdiesel.com" and you'll see that the 41's have the same problems world wide, smoking, overheating, blow by etc.
    I played the smaller props & change the reduction in the drive game, rebuild injectors, change injection pump with my 1st 41 for years and never got it to run/preform right, those engines just ain't got it in bigger boats. Call me or stop by the barn sometime and we can sit and talk about this.
    Its your rig and you run it they way you see fit.

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  14. #14

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    Fair enough, I'll stop by. Thx.

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    Volvo tech support wizards wbo have helped me say you should cruise at no greater rpm than 10 percent less than wot. Wot with a FULL load should be 3900-3950. Btw, a C2 propset is roughly equivalent to B3, as it does not flex as much, so you probably need B2, not C2, to get rpm up where you need it.

    6400 hours on my 44 with duoprop B2, in a 26-footer weighing 11,000 lb fully loaded. Cruise at 3100-3300 on step. Wot 3900. Rpm 1400 when cruising slow. 2/3 of hours have been slow by now.
    Richard Cook
    New Moon (Bounty 257)
    "Cruising in a Big Way"

  16. #16

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    Thanks Richard. I'll keep all of that in mind. FYI, supposedly the c2 is someplace between the b3 and b2, but not a full step smaller. Have c2 in hand and hope to try it out tomorrow and will report back re WOT rpms. The info is appreciated!!

  17. #17

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    Well, the C2 was not a success, just not quite enough prop to keep the boat firmly on step, and WOT up to 3850. Went back to b3 which works better, but might be slightly over-propping it. The true solution is to repower . . . but that is not in the cards for a while so watching the weight and running it harder that is optimal (but below Volvo spec) is going to have to suffice until then. Thanks for the help guys.

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