prop selection
 

I just bought a 2001 Diablo 180 with a 4.3L 190 hp mercruiser engine. The boat is great, and top end speed is almost 50 mph. However, it can't pull up a slalom skier at all. The prop is 14" diameter and 19" pitch (aluminum). The rpms at WOT is only 4000 rpm, and the rpm range according to the owner's manual should be 4400 - 4800 rpm. I realize I need to try a prop with a lower pitch. Hopefully, someone can help, and suggest what pitch I should try, and if I should stick with aluminum or go to stainless.

Thanks,

Todd

Re: prop selection
 

This should have been posted in the 'Prop Talk' section. Are you sure its a 19" prop? The 19 should have you up & towing a skiier without any problems and your rpms should be up close to the 4800 mark with that prop. I suspect, simply based on the numbers you provided, that the prop is a 21" or maybe higher. Its possible that prop has been repaired & is no longer a 19" (even though it may be stamped as such). It could also be that the prop hub is in poor condition & it spins a bit under load. I would suggest borrowing another 19" prop to see what results you get.

Also, open up the access panel to the back of your gauge cluster, locate the tach and give the little dial on the back a spin around then re-set it to "6 cyl". Sometimes the tach can get a little corrosion inside which affects the readout.

After you sort the above out, i would consider installing a pair of Smart Tabs. Do a site search here and you will find lots of information and satisfied buyers.

Re: prop selection
 

Hi Todd,
Welcome to the "What Prop Debate". Having tried six different props on my own boat I strongly recommend "Try before you buy". I agree with Mikeyt the figures don't seem to stack up. A friend had a 190 shabbah with the same engine as yours and he changed down from a 21" pitch alu 3 blade to a 19" High Five with great results. Totally transformed the the handling and performance. Remember every boat is different. Performance charts and tables are only a guide to give you a starting point.
Good luck with your choice.
Hammy

Re: prop selection
 

My prop is stamped as a 19" prop. From what I've read it doesn't make sense. It seems like most boats with this engine setup are having the problem with a 21 pitch prop, and going down to a 19 fixes things. I will check your suggestion about the tach gauge, and take my prop to the local marina to verify the prop is okay.

Re: prop selection
 

dont be switching pitch right of way. as this is an older boat i wonder what condition this prop is in. if it has been repaired i wonder what the diameter is now. a new prop now is generally 14 1/4 by ? . yes the rpms are really wrong. should i ask though did you have the boat trimed right? look on the side of the drive and you should see the gear ratio also. have the prop checked at your local prop shop.