Classic SeaCraft Community

Classic SeaCraft Community (http://www.classicseacraft.com/community/index.php)

- Performance (http://www.classicseacraft.com/community/forumdisplay.php?f=5)

- - I/O vs. OB (http://www.classicseacraft.com/community/showthread.php?t=21773)

Quote:

A 300 HP Mercruiser with Bravo Drv.900 #

I had a 300hp Mercruiser (7.4L) which is a 454 ci Chevy block and a bravo 1 drive, It was way heavier than 900 #, all together it was close to 1300#.

Quote:

I had a 300hp Mercruiser (7.4L) which is a 454 ci Chevy block and a bravo 1 drive, It was way heavier than 900 #, all together it was close to 1300#.

I don't know the weight, but the current 300HP Mercruiser is a multi-port fuel injected 5.7 liter,(350ci) small block.
Dave

I'd say closer to 1300 lbs for the I/O myself...I think the 5.0 merc in my Hiliner and bravo 3 is about 1100 lbs. The new 300 Yamaha should be closer to 575 lbs not 800.

Quote:

I had a 300hp Mercruiser (7.4L) which is a 454 ci Chevy block and a bravo 1 drive, It was way heavier than 900 #, all together it was close to 1300#.

I don't know the weight, but the current 300HP Mercruiser is a multi-port fuel injected 5.7 liter,(350ci) small block.
Dave

One site lists the complete package for a Mercruiser Magnum 5.7L 300 hp motor, transom mount and Bravo 2 drive at 1083 lbs.

Quote:

I had a 300hp Mercruiser (7.4L) which is a 454 ci Chevy block and a bravo 1 drive, It was way heavier than 900 #, all together it was close to 1300#.

I don't know the weight, but the current 300HP Mercruiser is a multi-port fuel injected 5.7 liter,(350ci) small block.
Dave

One site lists the complete package for a Mercruiser Magnum 5.7L 300 hp motor, transom mount and Bravo 2 drive at 1083 lbs.

A big block will always be heavier than a small block.

A small block will be heavier with a bravo 2 drive than a small block with a bravo 1.

My numbers come directly from Mercury (in brochure form).

Quote:

Since there are a lot of 23 cc's with o/b here, I can chime in and say that my i/o's top end has been around 41 mph burning about 20 gph. My optimal cruise is right around 27-28 mph, getting 2.8 mpg. This is with a mercruiser 250/carbed/alpha.
It does ride like a tank when i need it to. The funny thing about fishing space on this boat is that I fish most often with two guys and the engine compartment makes an excellent casting platform in the back.

Oldfielder,What's your WOT RPM?
I also have a 23 footer(Tsunami) with a 350 I/O with a Merc Alpha drive.I wish I could get 41 mph top speed.
I'm only getting around 36 at wot.
Maybe it's the weight difference and wind resistance,between the ctr console and Tsunami/Sceptre models.
It cruises nicely around 27 at about 3400-3500 rpms.

It was originally a 305 but the block was replaced with a new 350 short block.They transferred all the other parts to it,and I put a new intake and a 650 cfm Edelbrock 4bbl carb on it,so I'm assuming that I'm around 240-260 HP.
A mirage ss prop that seems perfect.Maybe it's the weight difference for the slower speed.
Also,the stand up canvas work,the radar arch,and some wet foam in the stringers may also be slowing me down.

Either way it rides awesome.It's stern heavy but it jumps on plane very fast,and the tabs easily correct any other ride issues.

I top out around 4400, which is really the bottom of my 4400-4800 range, so I may be slightly overpropped but I don't let it bother me.
As far as weight/wind resistance, you are probably spot on. I added a simple three sided enclosure this year to the t-top for a little break in November from the wind and I've lost a bit off the top. It's amazing how that little item changes things in the wind-even when docking.

Hit 39.5 today with the windscreen up, two big guys and about 50 gallons of fuels and 4 big fluke on board :)
Was burning exactly 20 gph and running in a slight chop(which the boat seems to like best)