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Author Topic:   Non-Whaler, 56-MPH Boat

shopguy posted 09-10-2008 02:33 PM ET (US)
I was passing through and noticed the prop talk. I have a 23ft 3600lb caravell bow rider witha 7.4mpi and bravo1 1.5 ratio. It runs 65mph at 4600rpm with Vengence 14x21 and it nose up out of the hole. Doesn't plane until over 20 mph it's just bad. It's really heavy at the stern. So far I borrowed a Mirage 14.5x21 and a hydrofoil on it. Made a huge difference. It planes with 1/4 throttle, doesn't loose speed in decent turns and top speed is around 58. I like it. My question is, with your experience is there a better prop than the mirage since I'm looking to buy one? I'd thought about the Solas Amita3 15.3x21 but they say it won't handle the 454. Another prop shop says the Powertech ofs 15.25x21 is the way to go. I think I've become the victim of asking to many questions and too many different answers. I don't expect to find one perfect prop, just don't want to waste money on something that won't be in the ball park. Is there something obviously better than the Mirage I'm using now? Any help PLEASE...
Thanks, Danny
Tom W Clark posted 09-10-2008 03:13 PM ET (US)
Danny,
The venerable old run-of-the-mill MIRAGEplus is an excellent propeller for your application. It is a fast, stern lifting propeller with a lot of blade area which is good for high horsepower applications and has relatively low rake (contributes to stern lift) for a high speed three blade.
There may well be a better propeller for your boat out there. You have to experiment and see for yourself. We can talk theory all day long, but in the end, the proof of the pudding is in the tasting.
Propellers you should consider for your application include the PowerTech OFS4 series as well as the Mercury Revolution 4. Both of these are four blades which may not be quite as fast at the top end but *may* yield better fuel economy and improved handling at normal cruising speeds.
Tohsgib posted 09-10-2008 03:17 PM ET (US)
I would think a Vengence 19" might be good. Problem is your numbers don't fly. 1.5 ratio and a 21" prop will NOT fetch you 65 @ 4600...maybe 60 on a good day. I ran a 21 Vengence at 5k with a 1.32 ratio and only fetched 64-65.
Tom W Clark posted 09-10-2008 04:18 PM ET (US)
Nick,
I think Danny meant to type 56 MPH.
jimh posted 09-10-2008 09:33 PM ET (US)
[Emended TOPIC based on Tom's estimation of speed involved.]
Tom W Clark posted 09-10-2008 09:43 PM ET (US)
Jim,
Danny's boat goes 58 MPH with the MIRAGEplus. Please emend the amendment.
Tom W Clark posted 09-10-2008 09:43 PM ET (US)
:-)
jimh posted 09-11-2008 08:14 AM ET (US)
Man, these non-Whaler boats are fast. How much horsepower does a 7.4-liter stern drive have?
Tohsgib posted 09-11-2008 11:13 AM ET (US)
Anywhere(from Mercruiser) from 315 to 440 naturally aspirated and 525 supercharged while still maintaining a warranty. Most were 330-385hp in the 80 & 90's.
TransAm posted 09-11-2008 11:28 AM ET (US)
Typically, a 7.4 Litre (454 cu. in.) engine produced 330 HP, but that could vary somewhat. Beyond that, other 7.4 Litre engines such as the 454 Magnum would produce 365 HP. Both were used in the Whaler Temptation line.
shopguy posted 09-11-2008 02:58 PM ET (US)
Oh man....my mistake and I'm very sorry you commented to my bad info. The vengence was a 14x23. Thank you all once again for the very helpful info. Danny
seabob4 posted 09-11-2008 07:41 PM ET (US)
TA,
454MAG, 385. 502MAG, 415. Both measured at the crank.
TransAm posted 09-11-2008 09:54 PM ET (US)
Bob, unless Whalers printed material, as well as others, is incorrect, 365 HP was indeed the rated HP on at least some versions of the 454 mag. Not sure where it was measured though. I had a friend who had a 22' checkmate that ran a 454 mag/365. Perhaps the HP may have varied from year to year.
Tohsgib posted 09-12-2008 09:45 AM ET (US)
No it varied from boat MFG and what engine and $$ you wanted to spend. They had a 420 and 440hp 454 back in the days(usually behind a TRS drive) until it was replaced with the 502 which is NOT a 454. The 420/440 was a handbuilt custom engine from Merc and NOT cheap so you only saw them in Cigarettes and 10M Fountains, etc. I had the 420/440hp cam in my 454. Baja and others offered the 385 Magnum as well as the 365, 350, 330, 310 or 315 in 454 versions along with the Super charged 454 also known as the SC525 which ironically only put out like 500hp but that is Merc's quirks.
seabob4 posted 09-12-2008 02:38 PM ET (US)
TA,
All Sterndrives lose HP because of the oil bath the gears in the outdrive live in. Hence, one manufacturer might state crankshaft HP, another might state propshaft HP. The Merc Racing #6 drive helped solve this "parasitic" loss by spraying the gears with oil. Reduced the HP loss by about 80%.
When I was with Wellcraft, Innovation Marine contracted with Volvo to build a 600 TRUE propshaft HP motor, competing with the Merc 600 SC. I believe that propshaft HP is what manufacturers should advertise.
Thosgib, yes, depending on the amount of money you wanted to spend, you could get your 7.4s/8.2s configured how you wanted them. But, in my opinion, some of this tended to stress the motors. Why not bore it out, such as the 500 Bulldog, bump the displacement up to 540 cu. in.'s, and get the same power with the engine working less? To me, I'll take cubic inches any day.
Anyway, that's gofast stuff. But I will have to admit, a triplet of 1200 HP Innovation Motors coupled with Arneson drives swinging 5-blade Rolla cleavers on a 43 Scarab...

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Author	Topic: Non-Whaler, 56-MPH Boat
shopguy	posted 09-10-2008 02:33 PM ET (US) I was passing through and noticed the prop talk. I have a 23ft 3600lb caravell bow rider witha 7.4mpi and bravo1 1.5 ratio. It runs 65mph at 4600rpm with Vengence 14x21 and it nose up out of the hole. Doesn't plane until over 20 mph it's just bad. It's really heavy at the stern. So far I borrowed a Mirage 14.5x21 and a hydrofoil on it. Made a huge difference. It planes with 1/4 throttle, doesn't loose speed in decent turns and top speed is around 58. I like it. My question is, with your experience is there a better prop than the mirage since I'm looking to buy one? I'd thought about the Solas Amita3 15.3x21 but they say it won't handle the 454. Another prop shop says the Powertech ofs 15.25x21 is the way to go. I think I've become the victim of asking to many questions and too many different answers. I don't expect to find one perfect prop, just don't want to waste money on something that won't be in the ball park. Is there something obviously better than the Mirage I'm using now? Any help PLEASE... Thanks, Danny
Tom W Clark	posted 09-10-2008 03:13 PM ET (US) Danny, The venerable old run-of-the-mill MIRAGEplus is an excellent propeller for your application. It is a fast, stern lifting propeller with a lot of blade area which is good for high horsepower applications and has relatively low rake (contributes to stern lift) for a high speed three blade. There may well be a better propeller for your boat out there. You have to experiment and see for yourself. We can talk theory all day long, but in the end, the proof of the pudding is in the tasting. Propellers you should consider for your application include the PowerTech OFS4 series as well as the Mercury Revolution 4. Both of these are four blades which may not be quite as fast at the top end but may yield better fuel economy and improved handling at normal cruising speeds.
Tohsgib	posted 09-10-2008 03:17 PM ET (US) I would think a Vengence 19" might be good. Problem is your numbers don't fly. 1.5 ratio and a 21" prop will NOT fetch you 65 @ 4600...maybe 60 on a good day. I ran a 21 Vengence at 5k with a 1.32 ratio and only fetched 64-65.
Tom W Clark	posted 09-10-2008 04:18 PM ET (US) Nick, I think Danny meant to type 56 MPH.
jimh	posted 09-10-2008 09:33 PM ET (US) [Emended TOPIC based on Tom's estimation of speed involved.]
Tom W Clark	posted 09-10-2008 09:43 PM ET (US) Jim, Danny's boat goes 58 MPH with the MIRAGEplus. Please emend the amendment.
Tom W Clark	posted 09-10-2008 09:43 PM ET (US) :-)
jimh	posted 09-11-2008 08:14 AM ET (US) Man, these non-Whaler boats are fast. How much horsepower does a 7.4-liter stern drive have?
Tohsgib	posted 09-11-2008 11:13 AM ET (US) Anywhere(from Mercruiser) from 315 to 440 naturally aspirated and 525 supercharged while still maintaining a warranty. Most were 330-385hp in the 80 & 90's.
TransAm	posted 09-11-2008 11:28 AM ET (US) Typically, a 7.4 Litre (454 cu. in.) engine produced 330 HP, but that could vary somewhat. Beyond that, other 7.4 Litre engines such as the 454 Magnum would produce 365 HP. Both were used in the Whaler Temptation line.
shopguy	posted 09-11-2008 02:58 PM ET (US) Oh man....my mistake and I'm very sorry you commented to my bad info. The vengence was a 14x23. Thank you all once again for the very helpful info. Danny
seabob4	posted 09-11-2008 07:41 PM ET (US) TA, 454MAG, 385. 502MAG, 415. Both measured at the crank.
TransAm	posted 09-11-2008 09:54 PM ET (US) Bob, unless Whalers printed material, as well as others, is incorrect, 365 HP was indeed the rated HP on at least some versions of the 454 mag. Not sure where it was measured though. I had a friend who had a 22' checkmate that ran a 454 mag/365. Perhaps the HP may have varied from year to year.
Tohsgib	posted 09-12-2008 09:45 AM ET (US) No it varied from boat MFG and what engine and $$ you wanted to spend. They had a 420 and 440hp 454 back in the days(usually behind a TRS drive) until it was replaced with the 502 which is NOT a 454. The 420/440 was a handbuilt custom engine from Merc and NOT cheap so you only saw them in Cigarettes and 10M Fountains, etc. I had the 420/440hp cam in my 454. Baja and others offered the 385 Magnum as well as the 365, 350, 330, 310 or 315 in 454 versions along with the Super charged 454 also known as the SC525 which ironically only put out like 500hp but that is Merc's quirks.
seabob4	posted 09-12-2008 02:38 PM ET (US) TA, All Sterndrives lose HP because of the oil bath the gears in the outdrive live in. Hence, one manufacturer might state crankshaft HP, another might state propshaft HP. The Merc Racing #6 drive helped solve this "parasitic" loss by spraying the gears with oil. Reduced the HP loss by about 80%. When I was with Wellcraft, Innovation Marine contracted with Volvo to build a 600 TRUE propshaft HP motor, competing with the Merc 600 SC. I believe that propshaft HP is what manufacturers should advertise. Thosgib, yes, depending on the amount of money you wanted to spend, you could get your 7.4s/8.2s configured how you wanted them. But, in my opinion, some of this tended to stress the motors. Why not bore it out, such as the 500 Bulldog, bump the displacement up to 540 cu. in.'s, and get the same power with the engine working less? To me, I'll take cubic inches any day. Anyway, that's gofast stuff. But I will have to admit, a triplet of 1200 HP Innovation Motors coupled with Arneson drives swinging 5-blade Rolla cleavers on a 43 Scarab...