Inboard Experts

[riprunner]

I have a 350 MPI left hand wheel on a 23 CC with a 1.5-1 transmission as well. The boat oringally had a 1.1 transmission that we swapped out because sail boats were passing us. The new one we put in was an older transmission that was originally right hand but we converted it over to configure it with the new engine. You could do this with the older ones I guess.

At 3200rpm I'm running 19-20knots on average at 10.5GPH and I'm spinning a 15/17 wheel. This seems a bit slower than knot working's boat. Any suggestions....?

[GetReel]

I'm hitting all the IB posts, slow in the office. Your prop is not sized correctly, the spec is 16 x 17 so I would guess thats the reason, also seems like your fuel consumption is a little high and may also be due to the prop. I am turning 16 x 16 4 blade at 1 and 1/2 tranny, 3200 is about 21 nph, depending on tide and wind, averaging about 8 gals per hour fuel injected, so you are close to typical numbers, the other post was in MPH so I think he was close also.I have played with the props and the original spec is the best, i kept my 4 blade after adjustments because I spent so much on it

[Gary Hill]

The engine need's to the recommended RPM's in all cases, if not it's like driving on the interstate in 3rd and you need to shift up. Craig's prop I used to get a idea where to go would only turn 4200 RPM's, like I said I'm running a 17 x 16 prop, which the prop shop did do some work on and I don't remember what that was.

[riprunner]

What is everyone else cruising at with thier 23 inboards?

I really hate to spend $500 on a new prop right now, but if everyone is 3-4 knots faster at cruise and getting better economy it seems like an expense well worth it.

[GetReel]

The original spec is 16 x 17, 3 blade, 5* degree cup LH on a 1.5 tranny. I tried a 17 and it too fat amd loud, the 15 spins in the hole.

[dsharp]

I don't profess to be an expert but an automotive engine turns counter-clockwise(left hand prop)You always look at a marine engine from the rear. on the 71 and 72 series borg warners the only box that reverses is the 1.9:1. They made a 2.1 to 1 and 1.9:1 to run pairs that used standard rotation engines. Most counter-rotating conversion change the timing chain for a timing gear. Cam turns same dir- crank rotates opposite direction. Some mercruisers used chains and everything ran counter. The starters are always different. Some people have tried to reverse the rotation in the borg warner but they won't hold up because the reverse clutch pack has fewer plates and discs. Physically it will do it but it will not last long. Most rudders are offset like a couple have noted to simplify shaft removal without dropping the rudder. I think Gary made the point that the most important thing about props is the engine has to be able to turn the rated rpm's at full throttle. Some rough rules of thumb are 1" diameter = 2" pitch. Reducing 1" pitch will pick up about 200-300 rpms. A cup will be about the same as 1/2" of pitch. There are really to many variables to try to compare what someone else is running. You can shift the weight in a planing hull and lose 300 rpm. Like I said these are rough guidelines. The best way is to run the boat with normal fuel load, gear etc and see where your at. You generally don't want to get to far off from square though. No expert-2nd generation boatyard rat.

[Gary Hill]

JEFF H,
What are your RPM's at wide open?

[Miles Offshore]

well, prop playing again- i went with the factory specs this time- 16x 17 5° cup- pick it up tomorrow and will put her on this saunday probably (i hope). (king fishing saturday, how about you gary?)

[GetReel]

4800 and about 29 NPH, done leave her there too long!

[Miles Offshore]

I got 24 knots at 3400 yesterday but my 4 barrel is knot working,(kicking in)lol. By myself with light fuel( 30 gallons). 13/14 gph. but what I liked though was the 21 knots at 2800 prms and 9.5 gph. this is the new 16/17 5°nibral i picked up off of ebay for 70 bucks - reconditioned for 120, and 40 for shipping= 230- sick