propellor help

stevewy · Post by **stevewy** » Fri Nov 16, 2007 1:59 pm

I have 454/330 mercruisers. What is the best prop and pitch? I'm interested in getting more high end rpm

franklyprice · Post by **franklyprice** » Fri Nov 16, 2007 3:42 pm

steve, What gear ratio do you have? Lacking that , what year is your boat?

Post by **dougl33** » Fri Nov 16, 2007 5:14 pm

Steve, If I remember correctly from your earlier posts (OK, I didn't really remember, I just looked at your first post!), you have a 78. If your gears are original then you probably have bw 1.91:1 gears. That being said, we also need to know what size your props are right now (diameter, pitch, cup) and what you're currently getting for rpms at WOT. Without knowing we can only guess. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Rissa · Post by **Rissa** » Sat Nov 17, 2007 5:32 am

quote:Originally posted by dougl33 Steve, If I remember correctly from your earlier posts (OK, I didn't really remember, I just looked at your first post!), you have a 78. If your gears are original then you probably have bw 1.91:1 gears. That being said, we also need to know what size your props are right now (diameter, pitch, cup) and what you're currently getting for rpms at WOT. Without knowing we can only guess. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img] If I am not mistaken that sounds like the same size we have on our '77. We had 19/17 props with 1 3/8 inch shaft. From what I understand now, only the "77 has that size shaft, all other year boat shafts are 1 1/4". Be sure you do check the shaft size BEFORE you order your new props. Question about paint on props? They took our old props and straightened them out great. They were supposed to polish them but, they just cleaned and painted them gold. Will the paint be bad about barnacles growing on the props vs. them being polished? I really hope we never need to use the old ones again but..... Stuff does happen, and a spare anything is ALWAYS GOOD! Marissa DeWitt "Miss Missy" Ocala, FL 1977 33 FBC

Post by **dougl33** » Sat Nov 17, 2007 6:24 am

Rissa, All gas powered 33's from 1977 till 1986 had inch and 3/8's shafts and 1.91:1 trans ratios. The props from the factory were 21x20 3 blade. In 1987, Bertram switched the gas boats to inch and a half shafts and 2.5:1 trans ratios. The props were 23x26 3 blade. All diesel boats (all years) were inch and 3/8's shafts unless ordered otherwise. Bertram never used inch and a quarter shafts on the 33's. At 19x17, your props have been altered from factory specs which is very common on older boats. The last set of 3 blade props I used before switching to diesels were 20x18 with a light cup. With those props I could obtain 4200-4300 WOT, depending on load and conditions. The last props I used before the conversion were 20x16 4 blade also with a light cup (I through a blade on the 20x18's and needed to get new props). These allowed me to turn around 4150-4200. You can do a search on the FBC section to see my exact results. I can't speak to the paint on the props as running gear growth is not the problem in the NE that is down south. I think it all depends on what they used and that the application was done correctly. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Rissa · Post by **Rissa** » Sat Nov 17, 2007 6:46 am

LOL Well how about that Doug. The shaft size difference was the excuse the prop place gave as to why they kept sending us the wrong props. I guess they were used to working on newer boats. Nice to know it was not just our year boat. Marissa DeWitt "Miss Missy" Ocala, FL 1977 33 FBC

Post by **dougl33** » Sat Nov 17, 2007 6:48 am

Rissa, Anytime you want to know anything about the production run just ask me![:D] Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

lobsta1 · Post by **lobsta1** » Sat Nov 17, 2007 7:40 am

Rissa,Steve If you have the original engines, on the valve covers there should be a sticker from Merc giving a WOT of 3800rpm. Bert tested our boats to 4000rpm with 21x20 props as Doug said. Previous owner put 21x19 props on when he added a humongous hardtop & full enclosure. He thought that was fine as the tachs read 4600rpm. That was WRONG! Bert modified the Merc wiring harness to work with the Detmar tachs & the Thunderbolt I ignition. Previous owner had the engines rebuilt & replaced the Merc ignition with Mallory Unilite distributers.I put new tachs in & ran direct wires to the coils. Found out with those props I was really only turning 3650rpm. I had the props scanned & repitched by Propscan to 21x18. With full fuel, water & two people on board, I now turn 3950rpm. Al

stevewy · Post by **stevewy** » Sat Nov 17, 2007 8:18 am

Thanks for the responses. I have a 1978 with the original engines. I'm not sure if my old tach's were reading correctly, but I have installed new ones (and had them tested) and a combination fuel flow/digital tach (which only jumps off of the tachs), and I know these are correct. Last year I had an MRI on the props. I have 1 1/4 shafts, 3-blade bronze. The specs are: Marked dia- 21, Measured dia- 21.0, mk'd pitch 20, pitch of wheel 20.29, cupping 0-.000 Radii averages are: bld1 20.41, bld 2 20.24 and blade 3 20.23 the other side averages are bld 1 20.02, bld 2 20.13, and blade 3 20.08. As I noted when I was considering re-powering, part of my motivation to re-power was the fact that I wasn't reaching high RPMs (top end with full tank of gas, no water, and 3 people was 3000) and therefore having slow speed. Since I've ruled out re-powering I've made a few changes. I cleaned the Starboard carb and replaced the fuel pump (this engine was running erratic and losing even more RPM - topping out at about 2700). After these changes Starboard is getting up to about 3400, port 3000. I then put new Mallory Distributors on. Starboard will now get up to 3800 and port about 3400. I'm thinking the port may also have fuel issues and planning on doing a carb clean and replacing that fuel pump in the spring. I'm hoping that one will also jump up to around 3800. It sounds like that is about what I should expect. I was thinking that my top end should be 4200 - 4600 and be able to cruise easily at 3200. However, from reading your responses, around 4000 seems to be about it. I live in Michigan, so I'm now up on blocks until April. Any suggestions or other thoughts you may have is appreciated

stevewy · Post by **stevewy** » Sat Nov 17, 2007 8:23 am

I should note, I put new shafts on in 2002. The originals may have been the 1 and 3/8 Doug noted. The current ones are 1 1/4

Post by **dougl33** » Sat Nov 17, 2007 10:59 am

I think if you do the same work on the port engine and drop the pitch down to 18 you should get your 4000rpms on both engines. Any particular reason you changed to inch and 1/4 shafts? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

stevewy · Post by **stevewy** » Sat Nov 17, 2007 12:09 pm

Returning from a weekend outing in 2002 my starboard engine overheated during a storm on Lake Erie. Concerned about safety (my wife and kids were aboard) I tried to manuever to a near island and anchor rather than risk continuing in 6's in heavy rain on one engine. I ended up being up beaching it and washed into a rocky area. I had to replace both rudders, shafts, struts, and props. The shop that did the work must have made the change. Until I read your post I didn't even know the shaft was changed. I would assume now, he changed it to save a few bucks on his end. I was told everything was being returned to it's original state. I bought the boat in 1993. I am the second owner. I guess it's possible that the original shafts may have also been changed prior to my ownership, and the repair was done replacing what was there. Thanks for your suggestion. What do you think I'll get if I leave the pitch as it is, but do the fuel work? It costs about $400 to rework the props, and I'm not sure how many times that can be done. If I can get 3800/3900 with the fuel work on the port side, would you still recommend that I change the pitch?

Post by **dougl33** » Sat Nov 17, 2007 3:56 pm

As Al pointed out, your valve covers probably state that 3800rpms is WOT. Most of the later 454's owner's manuals (Crusader and Merc) will state a WOT of 4200-4400rpms. Its hard to day what you'll actually get if you do nothing to the props. I would probably still have some pitch taken out so you'll always be assured of reaching 3800-4000rpms when the bottom starts to foul. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

franklyprice · Post by **franklyprice** » Sun Nov 18, 2007 2:20 pm

Rule of thumb is 1" of pitch = 200 RPMs but I have to tell you , if you're running the correct pitch and still way off with wide open RPM, there is probably another reason than prop pitch, like a severely fouled bottom or props or under-performaing engines.