I have a 21ft cruiser with a 454 twin turbo spinning through a T400. It hits 6k rpm and about 80mph on GPS. The prop is a steel 12-14. The gears are 1.29 in the Casale. At 4k rpm I'm running about 45mph. I would like to bring the r's down a bit at cruising speed. Any thoughts?
[This message has been edited by 78DiMarco (edited June 27, 2002).]
In my 21' Howard with 547 ci, 1071 mooneyham,2 1050's and superchiller and Turbo 400 I use 48 % overdrive with a 12x16 steel 2 blade it runs 107-109 mph at 6200 rpm and cruises at about 35 mph at 2500 rpm. If the prop you have works good for you, you could go up on the gear to at least 37% OD. At 37% you don't have to cut the water jacket out of your V-drive. Of course I'm assuming you have a split case. I really like the larger gears. You can cruise without turning the motor very hard.
Originally posted by VD CRUISER:
In my 21' Howard with 547 ci, 1071 mooneyham,2 1050's and superchiller and Turbo 400 I use 48 % overdrive with a 12x16 steel 2 blade it runs 107-109 mph at 6200 rpm and cruises at about 35 mph at 2500 rpm. If the prop you have works good for you, you could go up on the gear to at least 37% OD. At 37% you don't have to cut the water jacket out of your V-drive. Of course I'm assuming you have a split case. I really like the larger gears. You can cruise without turning the motor very hard.
VD thanks for the reply, The prop does work well for me and I was thinking of going to the taller gears. I have never changed the gears in the drive. Sound like I need to locate the 37's and that will give me more of what I am looking for.
you didn't say if you are running a 3 blade or 2 blade prop.try running 12x16 3 blade or better. it may change the lift or aditude of the boat, or call tom at menkins @ 1-530-885-0531.
Tom is the man - give him a call and he will get you all set up.
Tom is the man - give him a call and he will get you all set up.
29's may be a tad on the short side, but I bet more pitch would give you some of what you're looking for too. I have an 82 DiMarco 21' with a pretty stock BBC and also run a 12x14. That prop allowed me to pull 29's even with the much lower horsepower I am running compared to your setup. I've stepped down to 22's and it's a little happier now.
78DiMarco, If your engine is only turning 6000 RPM now a big gear change would probably pull it down more than you want. VDcruiser is able to pull a bigger gear because he has a blower,and makes big power at low RPM. If you over gear your turbo motor it will become lazy at the bottom, making you ALWAYS take off in 2nd gear. I think a little more pitch(15) and a little more gear (32%) has a good chance of doing what you want.TOM..
Thanks for all the input. Tom, your suggestion for a little more pitch and a bit more gear may be what I need. I may try the prop first and then the gears.
By the way I have a 3-blade prop now.
Just have to say thanks to Tom for helping with my set-up in my 63 Mandella Flat. I couldn't have done it so easily without his help. (prop and gear selection)
Also, Tom, just wanted to let you know that the prop coating is working very well. I have about 10 hrs. on the prop with no signs of wear through! That stuff works great. I'll send you a picture in the next couple of days.
Take Care,
Barry
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