Props & Speed

bosdockpilot · Post by **bosdockpilot** » Tue May 02, 2006 3:08 pm

Oh well Al...it was just a thought[:)] Did you get my IM? Steve

Brian Davin · Post by **Brian Davin** » Tue May 02, 2006 3:54 pm

Steve, I'm repowering from gas to diesel and have been concerned about air flow. My '90 FBC has both facing forward. The forward ones have a 5" diameter vent hose directly into engine compartment. The ones aft, also facing forward, have 4" vent hoses that go into engine room and then connect to bulkhead into side cockpit lockers to apparently vent the aft bilge. I'm planning on replacing aft ones with 5" vent hoses dumping straight into the engine room, leaving the rear bulkhead opening just open. Brian '90 Bertram 33' FBC Never Say Never Guilford, CT (Homeport) Kinnelon, NJ (Home)

fishybusiness33 · Post by **fishybusiness33** » Wed May 03, 2006 9:02 am

IN RESPONSE TO YOUR REPLY TO MY MESSAGE WITH THE QUESTIONS YOU RAISED, I HAVE COPIED YOUR RESPONSE SO I CAN RESPOND TO EACH QUESTION THE BEST I CAN. HOPE THIS HELPS. OKay not you've got my interest- those are great speed numbers- where I would like to be, and I'd like to know some details about your boat. What HP rating are your 3208's? Mine are 260, and I'm thinking of bumping them to the max non-aftercooled rating of 320 HP. MINE HAVE BEEN BUMPED TO ABOUT 300. What shafts are you turning? Bertram gave me the 1.375" ones which are marginal now. MY SHAFTS ARE THE SAME AS YOURS AT 1 3/8THS. What gears do you have? Mine are the Twin Disk MG502-1, which are rated for 260 HP. So, if I upgrade engines and not gears they would be technically underrated. Although a Twin Disk guy told me they should be fine it would still be a little spooky. I ALSO HAVE TWIN DISK RUNNING A 1.54:1 REDUCTION I'm turning 20x22 props and I'm quite surprised at your numbers with 21x21's. Would have thought that the pitch dictates speed more than the diameter but maybe I need to re-think that. I also have a set of balanced 20x23's but I have yet to try them out. I TRIED SEVERAL DIFFERENT SETS OF PROPS AND SETTLED ON THE 21X21 WITH A LOT OF TWEAKING ON THE CUPS. THERE ARE SEVERAL 33s IN PORT ARANSAS AND I WAS ABLE TO BORROW PROPS TO TEST ON MY BOAT AFTER I PURCHASED HER IN '97. I WAS AMAZED AT HOW MANY VARIATIONS OF DIAMETER AND PITCH WERE BEING RUN ON APPARENTLY SIMILAR RIGS BUT WE ALL SEEM TO HAVE OUR ON PREFERENCES BASED UPON THE CHARACTERISTICS OF EACH BOAT. THE 21X21 WORK WELL FOR ME BUT I SUGGEST THAT YOU TEST AS MANY DIFFEERENT VARIATIONS AS YOU CAN GET YOUR HANDS ON. I can get your WOT and cruise speeds with an empty boat, clean bottom, and a 1/3 or less tank of gas, but loaded down I can't approach them. Can you achieve 21k cruise with a full tank of fuel with people on board too? If so, I've got something wrong. My boat (and I'm sure this is true of them all) seems to want to live at 21-22 knots, the ride feels right there. Until I can manage to get those 370 BTA's or a maybe strong yannies, I'd like to try to get there with what I have, such as you are. MINE SEEMS TO BE ONLY MINIMALLY AFFECTED BY THE WEIGHT I AM CARRYING. THE BIGGEST FACTOR SEEMS TO BE HOW CLEAN THE BOTTOM IS. I ALSO SPRAY RATHER THAN ROLL THE BOTTOM PAINT. INTERESTINGLY, WHEN I STARTED DOING THAT MY SPEED INCREASED BY ABOUT 2 KTS OR MAYBE I AM JUST TRYING TO JUSTIFY THE EXTRA EXPENSE AND IT WAS REALLY DUE TO THE EXTRA CLEAN BOTTOM. I ALSO TRY TO KEEP VERY CLEAN AIR AND FUEL FILTERS RUNNING AT ALL TIMES. HOPE THIS HELPS AND GOOD LUCK.

Post by **dougl33** » Wed May 03, 2006 9:07 am

Matt, How long have you been running the bumped up Cats on the TD 502's? Everything I've ever seen/heard states that 270 is the max for the 502's. Some people (from boatdiesel.com) seem to think that they'd be ok at 300-320, but no one could say for certain. How hard was it to bump up the Cats to 300hp? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Sean B · Post by **Sean B** » Wed May 03, 2006 12:54 pm

It would have to be a change of the injector pumps, or a rebuild of them with the 300 HP rated parts, and some governor springs and settings changed. Injectors are the same. Well, all that is true if he has the same CAT 3208 01Z engine blocks that I have. The 01z's are the heavy, last forever blocks if not a "TA" engine. They are the same blocks that they used for the max HP aftercooled engine models, which at the HP ratings above 320, have normal lifespans. There are older 3208T blocks that you can't monkey with too much, but it sounds like Matt has the 01z's. That is encouraging, those speed numbers, considering we have essentially the same boat. I wonder if all I need is a serious bottom job. On my boat the condition/cleanliness of the bottom make a huge difference too. Matt, you mentioned cups- do you know offhand what your 21x21's cup size is? The 20x23's I'm planning on trying have a #4 cup. Ever twist off a shaft? Do we ask enough questions? Sean Burlingham "Island Time" 1987 Bertram 33 SF Melbourne, FL SBurlingham@cfl.rr.com

mak6190 · Post by **mak6190** » Thu May 04, 2006 12:17 pm

Hello you all ! Matt's numbers are Great! What I don't understand is how Matts weight does not affect his speed. In my case it does " BIG TIME". I can see his WOT at 27 kts. on a good day running very light, 1/4 tank, no water, 3 onboard just cleaned becuase I have seen 24.8-25 on my Cat 3208 275hp. My questions are : Does he have a generator onboard , what about a water tank? What about Air con? 3 anchors, windless with 100' of chain, spare props , 315 gal. of fuel, three cases of beer, 40 gal of water ,2 Igloos with 8 bags of ice, Magama BBQ pit, outriggers,9' life raft on the bow, 15 hp merc, 4 penn 50s, TV, Nitendo, fridge, 4 on board, tackle boxes, VHF, tool box, spare filters, belts ,SSB,Fishfiner , autopilot, etc.. etc.. You don't know how much weight you can put on until you need to dry dock which is when you genrally clean out all the XXXX

! Best cruise I have with the 275 hps loaded as described is 18-18.5 kts @ 2350 rpm.

photo finish · Post by **photo finish** » Thu May 04, 2006 5:39 pm

only 3 cases of beer?

Capt. Ed · Post by **Capt. Ed** » Fri May 05, 2006 4:07 am

Tragic event, the store must have had only had three cases, you need to get there early you know! 1979 Bertram 33' FBC ALEXANDRA Port Richey, Florida HAVE YOU SIGNED UP FOR BERTRAM PRIDE '06 yet? DO IT NOW... SPACE IS LIMITED!

Mikedcabo · Post by **Mikedcabo** » Sat May 06, 2006 1:33 am

Maybe the gallon of rum just isn't a weight factor

Sean B · Post by **Sean B** » Sat May 06, 2006 6:35 am

quote:Originally posted by mak6190 What I don't understand is how Matts weight does not affect his speed. In my case it does " BIG TIME". I can see his WOT at 27 kts. on a good day running very light, 1/4 tank, no water, 3 onboard just cleaned becuase I have seen 24.8-25 on my Cat 3208 275hp. My questions are : Does he have a generator onboard , what about a water tank? What about Air con? 3 anchors, windless with 100' of chain, spare props , 315 gal. of fuel, three cases of beer, 40 gal of water ,2 Igloos with 8 bags of ice, Magama BBQ pit, outriggers,9' life raft on the bow, 15 hp merc, 4 penn 50s, TV, Nitendo, fridge, 4 on board, tackle boxes, VHF, tool box, spare filters, belts ,SSB,Fishfiner , autopilot, etc.. etc.. You don't know how much weight you can put on until you need to dry dock which is when you genrally clean out all the XXXX

! Best cruise I have with the 275 hps loaded as described is 18-18.5 kts @ 2350 rpm. Mike Kohlhofer TUCUSO Venezuela Yeah those numbers do seem to be pretty atypical Sean Burlingham "Island Time" 1987 Bertram 33 SF Melbourne, FL SBurlingham@cfl.rr.com

photo finish · Post by **photo finish** » Sat May 06, 2006 7:06 am

I've got my boat on the hill to replace shafts (wrung one off last week) and plan on playing with props while I'm out. My boat has the 300 6bta's, which are a lot lighter than Sean's 3208's and rated at 40 more hp each. Your performance numbers are currently better than mine, so I wonder if I've been propped too lightly with 21 x 20 4 blade props (1.53: 1 ZF gears). I know my particular boat is heavy, with extra fuel, etc. that I run 28,000 lb loaded. Is your boat significantly lighter? quote: Fraser, How did you snap a shaft?And how did you handle the situation and what shafts are they?

TBonedad · Post by **TBonedad** » Mon May 08, 2006 3:39 am

Tim - I was as lucky as you can get and still break a shaft. I had noticed some heavy vibration earlier, so I shut down that engine. Back at the dock I fired it back up to help maneuver into the slip. We had the stern line attached to the dock and I shifted the stbd engine into reverse just to swing the bow in and "POP," there she went. I don't know why it happened, but it broke right behind the strut, just where the taper and keyway start. It looked like there had been a crack there for some time. I should be back in the water this weekend.

photo finish · Post by **photo finish** » Mon May 08, 2006 6:37 am

Wow, Are they 13/8" aquamet 22 shafts? my 81 came that way from the factory. You may want to consider the temet25 shaft for replacement that is what i put on when i repowered.

TBonedad · Post by **TBonedad** » Mon May 08, 2006 10:30 am

1 1/2" Aquamet 19 shafts. They should have been strong enough, which is why I think I had an "issue" which prematurely weakened it.

mak6190 · Post by **mak6190** » Fri May 12, 2006 10:30 am

Just to clear up my last post, " Three cases of Beer" that are used for the sole purpose of "cooling down" during trolling because down here ever body drinks Scotch which we usually have 2 liters on board at any given time. Too much Beer and Whisky is risky ! Whisky and beer , have no fear ! As far as shafts go, I would like mention to everyone that Aquamet has not taken on too well down in our area according to the techs that do service on shafts. It seems to be much more prone to faliure because of the effects of electrolisis, more than SS 316 or even SS 304.I am not talking Aquamet's strength or ability to handle more HP , just durability. So after some time they just snap where they suffer the most from electrolisis. Also, the more rigid the shaft ( Aquamet) the easier it will snap before bending. I am currently using 304 SS shafts and they have been in use for about a year and a half. I figure I will probably bend one before they go out because of corrosion. I would also like to mention that I bent a shaft one time and I could not find anything floating around that could have been the culprit at the time of the incedent. When I pulled the boat out of the water I found that my recently replaced shaft anode was missing. I now believe that the anode came loose and hit the prop while I was going almost all out 21kts+ and a terrible vibration kicked in. I thought I picked up a rope or plastic bag. Was not the case. After close inspection the prop had a hairline crack as the hub and 1 of the blades had a shinny spot on it where I think the anode came in contact with the the prop at high speed, bending the shaft at the tip "only". So it's good to keep an eye on them anodes just to make sure they are on tight. Mike Kohlhofer