New 454 thread

[Craig G]

Hello all, I have made 4 posts to the 454s doing well thread, but they never show up, so I thought I would start a new one. No problem posting on other threads. I have Merc 454 EFIMPs in my Bahia Mar with 18 x 20 props and I am getting similar numbers like Peter. I generally cruise about 20 kts on the GPS which equates to 2500 - 2600 rpm depending on load and sea conditions with a WOT of only about 3700 rpm. I realize it is over propped, and has been for the 10 years I've owned it, but it accelerates very quickly right up on plane. Last year, I bought a pair of 17 x 18 wheels from Mike Kennedy, and finally installed them yesterday. I think it will be under propped now as I think 18 x 18 would probably be best. Stay tuned for an update, it is a beautiful day in South Florida today, so I will be going out for a spin in a couple hours with a full report.

[Craig G]

I just got back from a wonderful lunch with my wife at Kalutz on the ICW in Fort Lauderdale and tested out my 17 x 18" wheels there and back. The numbers are exactly what I was hoping for.

4400 WOT 30kts
3500 rpm 25kts
2900 rpm 20kts
2500 rpm 17kts

Normally, I would cruise at 20 kts and that used to be 2500 - 2600 rpm, and now it is more like 2800 - 2900 rpm. It surprisingly doesn't seem to accelerate on plane any quicker than it did with the 18 x 20 props. The transmissions do seem to have a new sounding whine at idle while in gear though.

[Stephan]

Craig-
I think that is very close to what I get. I have 1989 carbureted Crusader 454s in a light FBC.
I do note that the props are stamped 18x18 but measure out to 17.5x17.
How I do love the rumble of those engines at lower RPMs and the howl above 3,500...
Well done,
S

[Craig G]

Hi Stephen, thanks for the info. My boat appears to be pretty light based on how it sits in the water. My entire chine is above the water, and at the transom, the chine is about 3 1/2 inches above the water. My boat sits a little nose low probably due to the hard top and stainless steel marlin tower. Does anyone else have any rpm/speed data on their 454 powered 31s.

[PeterPalmieri]

My over propped numbers, 1985 merc 454s.
Wot
3900 port
3800 star

2000 13kts
2500 20kts
3000 24kts
2750 22 kits

When propped proped I think the number is 19kts at 2800

[Craig G]

Peter, I had virtually those same numbers with my 18 x 20 props. Looks like I still cruise at 20 it's, but at 2800 - 2900 rpm verse 2500 - 2600, now that I have 17 x 18 props.

[Tony Meola]

Peter

I believe you had 17X17's, and you were turning up close to 5000 RPMs on the top side. So looks like the answer might be, take the 18x19's down to 18x18 or the 17x17 up to 17 x 18. I have a feeling those two changes will get you closer. Change them both play with them then you might find they both work and you have a spare set, and or sell one set.

Given the price of new props, I would keep a spare set and just have a prop shop play with them. Buying an extra set will be costly.

[PeterPalmieri]

Thanks tony. Everyone says B&S is the best ont he island. I've got numbers on the current props and that seems to be all I need along with where I want to be. When we swap props in the spring I'll rerun to get numbers on the spare set. Send them out too and I should be good.

[Craig G]

I just put my boat back in the water after much work including new shafts and re pitching my 18 x 20 props to 18 x 18. It is perfect now, full of fuel and 2 people on my 454 EFIMP powered Bahia Mar, WOT was 4400 rpm and 31 knots. Cruising at 20 knots was about 2700 rpm. WOT with the same props at 18 x 30, WOT was only about 3700 rpm and 27 knots. Frank and Jimmie's prop shop in Fort Lauderdale got it right after asking me what kind of boat, approximate weight, horsepower, and gear ratio.

[Bertramp]

20 kts at 2,800 RPM....a very light bahia mar with approx 60 gals of fuel.
Crusader 454s
It will plane on one engine.
Not sure of prop size until I haul for bottom paint.