Props & Speed

robert watters · Post by **robert watters** » Tue Jan 31, 2006 5:21 pm

Last year just before Hurricane Katrina hit I finally reached the point of discontent with the speed capability of my 33SF. I put another 6000 into new heads, injectors and turbo for the stbd 3208T cat to match the work that I had done the previous year (involuntarily) on the port diesel. I then had to redo the props because both props had required re-working the previous year to take account of the mismatched power output of the two diesels. I started the props off at the marking stamped on the props 21 x 22 and sent them off to the nearest propscan (some four hours by car) . Took it out for the first time today since the hurricane, and bottom has now five months of growth, but the engines wouldn't get higher than 2100 rpm and achieved only 17.2 kts by gps. on a fairly calm day, averaged with and against the wind. Time for the props to go back to propscan with instructions that i want to achieve 2800wot. Anybody have any idea of the ptich that will achieve the objective?

Post by **dougl33** » Tue Jan 31, 2006 5:35 pm

Robert, Hopefully some of the other Cat guys will hime in, but I think the problem maybe the engines and not the props. You're only getting 17.2 knots at 2100 rpms, which I think is about the right speed for that rpm. If the boat were over-propped, you'd get more than 17.2 knots at WOT of 2100 rpms. Do they turn up to WOT with no load? I would make sure you check that before you mess with the props. If you haven't done so already, head over to boatdiesel and spend $25 for a membership. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

billb · Post by **billb** » Wed Feb 01, 2006 1:42 am

Robert: my 33sf has 270 hp cats in it and it has 21x22 props, speed with "clean" bottom and shafts is 21knots at 2400 rpm.. first thing is haul the boat, clean the bottom and shafts,then take her out and see if she will do 2850 loaded....dont change pitch, until you run the boat with a clean bottom...five months is a lot of growth, and it will definitely slow it down a ton!!!!!

Sean B · Post by **Sean B** » Wed Feb 01, 2006 7:39 am

I've got same the engines, and am putting on newly scanned and mussell-buster coated props, 20x23 w/ #5 cup, next Monday. Will report on the results. Currently have 20x22's with #5 cup, and I'm slightly under-propped. This is the standard factory setup. 20-21k cruise at 2500 RPM, and 24k WOT at 3050 RPM. With the right prop pitch the 3208 should top out at 2850 with a loaded-down boat, that is the goal with the slightly larger props. Under-propping never hurts anything of course but I want to go a little faster. Your props are an inch larger than mine in diameter, but the pitch is the same so I am supposing that your boat is propped correctly. A dirty bottom will slow you down MASSIVELY, as I have confirmed myself. Get a diver to clean it, or better yet, haul & pressure wash the bottom, it's much cheaper than re-bending props. Then see what's up. Also check the WOT no-load as Doug said. Do it with warm engines though and don't worry, they won't blow up. Should get 3000-3050 RPM Sean Burlingham "Island Time" 1987 Bertram 33 SF Melbourne, FL SBurlingham@cfl.rr.com

Post by **dougl33** » Wed Feb 01, 2006 8:02 am

Robert, I just rememebered that you have a tower. While that will slow you down some, something doesn't seem right. I still don't think its a prop issue. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

photo finish · Post by **photo finish** » Wed Feb 01, 2006 1:26 pm

Clean the bottom......... I lose 3knots with just a tiny bit of growth Tim Stamm Photo Finish 1981 33' Bertram FBC

richcatch22 · Post by **richcatch22** » Wed Feb 01, 2006 1:49 pm

Check the fuel filters too. Capt Rich Catch 22 1989 33 FBC

Sean B · Post by **Sean B** » Wed Feb 01, 2006 2:06 pm

Good point Rich. Always a good idea to change out fuel filters first if you're having power troubles. I think clogged air filters can do it to you too. They also don't necessarily look dirty when they are clogged. Any black smoke when running? Clogged air filter should manifest as lots of black smoke from air-starved diesels Sean Burlingham "Island Time" 1987 Bertram 33 SF Melbourne, FL SBurlingham@cfl.rr.com

Capt. Ed · Post by **Capt. Ed** » Wed Feb 01, 2006 4:55 pm

I have the bottom cleaned every month in the summer and every other in the winter. Else I lose speed and burn more fuel! 1979 Bertram 33' FBC ALEXANDRA Port Richey, Florida

robert watters · Post by **robert watters** » Wed Feb 01, 2006 4:59 pm

Thought it was good advice to check no load WOT, so did it today on warmed engines; right at 3050. Fuel filters were just replaced. I'm having boat hauled in next couple of days, so I'll see just how bad growth is. It's a pain not to take props off while it's out, but agree that I need to give it a run on a clean bottom before I re-pitch.

Mikedcabo · Post by **Mikedcabo** » Thu Feb 02, 2006 2:12 am

Well it's just good to see you'll be getting back in the swing of things soon. We've been in the Tchefuncta since Katrina-don't know how she'll run either but we'll find out soon. Weather and work have been getting in the way.Good luck.

photo finish · Post by **photo finish** » Thu Feb 02, 2006 4:09 am

Robert , Why do you need to take the boat out to clean the bottom...can you not send a diver down? Tim Stamm Photo Finish 1981 33' Bertram FBC

robert watters · Post by **robert watters** » Thu Feb 02, 2006 11:42 am

Tim; I had the bottom cleaned by a diver just before the hurricane (August) and it's now been 2 1/2 years since I had the bottom anti-fouling renewed. The boat has to come out of the water for painting the topsides (neighboring sailboats scratched it up pretty good just before they sank), so I might as well have the bottom done at the same time. I'll get new outriggers, canvas and paint from the insurance company, so it's an ill wind that did blow some good!

robert watters · Post by **robert watters** » Thu Feb 02, 2006 11:44 am

Mike, I'll probably be slipping it in Madisonville after it gets out of Schuberts, so I'll look for you.

robert watters · Post by **robert watters** » Mon Feb 13, 2006 5:26 pm

Pulled the boat out of the water today and found that though there was some growth on the bottom it wasn't really that bad. Also found that the port prop had a dinged blade from some submerged post katrina garbage, so I'm going to have to pull them both. After reading all of the posts on propping the boat I'm beginning to feel that I must have a very heavy boat (ok it does have a full tower, heavy chair (really heavy) and extremely heavy old model Lee outriggers. Still I have to re-pitch the props to get the rpm up to 2800, and reading these earlier posts I've come to the realization that growth on the bottom would have affected speed of the boat but surely wouldn't have affected the ability of the engines to turn the props at max revs, so the 21 x 22 pitch must just be severely over-pitched. I suspect the shop will have to take them somewhere between 19.5 and 20 to turn 2800 rpm.