Inboard Propeller Selection

omaier · #1 09-09-2002, 09:22 PM

I have a '76 SC23 Inboard that was repowered with a 230 HP Yanmar diesel. I currently run a 16x17 3 blade w/ light cup (Michigan Dynajet). The boat cruises at 28-30 kt and tops out at 33 kt.

My primary concern is initial acceleration out of the hole. When I have a load of people or full fuel tanks, it is difficult/impossible to get the boat over the hump. But, once over the hump and on plane, the boat accelerates and responds very well.

I was considering a 17x17 4 blade to help with initial acceleration.

What do you fellow inboard owners run? Any thoughts on what size propeller to use with my setup? How do the other inboards perform during initial acceleration?

Thanks in advance for your help!!

Mike

Miles Offshore · #2 09-09-2002, 10:51 PM

Hey Mike, the wheel you are currently turning is the correct wheel according to the literature I got for my 78'. I originally bought a 17/17 with slight cup for mine, but it would only turn up 3800 rpm's instead of the recommended 4200-4400. So I had it cut back to 16x17 with no cup and lost several knots but turned up the correct rpm's(not sure if this was good or not,better for the moter for sure)As far as getting over the hump goes, do you have trim tabs?? I run 12x12 Bennets on the outside chine and seems to help a lot getting out of the hole. I notice they work a lot better with a lighter load than with a full load. I actually would recommend an additional set of 12x12's on the next chine inboard to really work quickly witha heavy load. Tabman suggested this to me when trying to work mine out. Incidently , those 12x12's are as big as you can go on this boat. Anything larger and its wasted area. Hope this helps, sounds like your rig really flies, love having another inboard guy on the in-board.lol-craig

omaier · #3 09-10-2002, 10:56 PM

Miles Offshore,

I have a set of 12x12 Lenco tabs installed and they do help substantially.

What power do you have in your rig? What is your reduction ratio? What kind of performance do you get?

Any other inboard guys out there???

Miles Offshore · #4 09-12-2002, 05:34 PM

Hey Mike, I run a 350 Magnum with a 1.5 to 1 borg warner gear.(280 hp) I hear of folks (Capn Skip for one) getting better performance than I but I generally cruise at 21/22 knots with about 25 on the high end. Normally around Cape Henry/mid atlantic-ocean here that is about all you can do and still be comfortable in this size boat(I like my fillings in my teeth thank you). Lets see, Dan here has an inboard, capt Skip also has one,Gary has one and you have one!! Long live Inboards!!!

Miles Offshore · #5 09-12-2002, 05:37 PM

And by the way, mine originally came with a diesel in it but I am not certain about the data on it, but mine is a city bought boat(Va Beach bought 3 of them, all deisel powered). I understand the police didnt like them because they were too noisy so they were retrofitted with gas. I got lucky in the fact that my fuel tanks were only 3 yrs old when I picked up the boat at auction.craig

John R · #6 09-12-2002, 08:41 PM

Were you able to find the auction online? Or was it local?

Anyone know of any good auction sites?

Thanks...

Miles Offshore · #7 09-14-2002, 06:43 PM

Hey John, it was a local city auction held every summer- they still have one left but who knows when they will get rid of it. If I hear of it I will post it. craig

white hawk · #8 09-26-2002, 09:43 PM

Hi guys, another inboard fan here. I've got a '79 23 footer, 350 chev/Mercruiser conversion-260 hp. I too am running the 16X17 with a slight cup in it and get 34 mph top speed. Out of the hole is good and I do use 12X12 Bennets. I cruise at 22/25 mph and love the ride. Here in Jupiter the inlet is somewhat notorious for the standing men created when tide fights wind. Some Coasties capsized a 23 boat in it a while back. The Seacraft with it's low center of gravity bulls through this mess keeping me high and dry. Love it. I've heard the four blade will improve hole shot but you will size down a little on diam and pitch. All the wisdom I hear is that prop selection is largely trial and error. Sheesh. Luckily a local prop shop let's you borrow what they call "try props". Saves a lot of money.

omaier · #9 10-02-2002, 11:04 PM

White Hawk,
Sounds like our performance is very similar. Do you happen to know what kind of reduction ratio you have as well as your full throttle RPM? also, what kind of GPH and range do you get with the gas engine?

A separate question ... does anyone know how many inboards were produced?

Mike

white hawk · #10 11-16-2002, 08:40 PM

Sorry I haven't been around for quite a while. In answer to your question I run A 1.5:1 Borg. I don't know what my GPH is but it's not much. I return to the marina after a day of trolling and spend $12 to $15 bucks to top it off. Unfortunatly I just sold it to a guy that lives in N.J. He is picking it up Monday morning to transport home. I will be boatless for a few months, and then begin looking for a flats skiff since I will be moving closer to the Indian River. Good luck with your inboard special interest group.