User Tag List
Results 151 to 156 of 156
-
01-19-2018, 12:34 PM #151
I feel you hit the nail on the head with merc getting it pretty much right. The way I look at it and do it is, depending on how much material I remove any where that would effect cc volume to improve flow/velocity I replace the material else where with epoxy. Also depending on porting I'll change volume. I fool mostly with bass boats, so I normally tighten em up a little to add the needed low end to mid range needed for the heavier boats when raising boost/ transfer timing that causes the ports to be larger and slowing down velocity. On the inlet side velocity is the most important factor, without it, you ain't got nuttin. You can have all the flow ya want, but if it's slow, it's a turd.
-
-
06-08-2020, 02:56 PM #152Screaming And Flying!
- Join Date
- Feb 2015
- Location
- Ontario
- Posts
- 8,091
- Thanks (Given)
- 205
- Thanks (Received)
- 321
- Likes (Given)
- 1921
- Likes (Received)
- 2005
- Mentioned
- 2 Post(s)
- Tagged
- 0 Thread(s)
-
dwilfong liked this post
-
06-21-2020, 07:15 PM #153Junior Member
- Join Date
- Mar 2018
- Location
- Michigan
- Posts
- 15
- Thanks (Given)
- 0
- Thanks (Received)
- 0
- Likes (Given)
- 0
- Likes (Received)
- 1
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
I background is around snowmobile race engines and have only been working on outboard motors for 15 years. The extent of outboard performance has been limited to jetting to get improved performance. In the snowmobile world, we look at horsepower per liter. The maximum horsepower per liter today (it has been creeping up over the years) is 300hp/liter. As I have not been involved with racing outboards, I have not heard of an outboard making anywhere need that. A 2.5 liter outboard would be around 750 hp. I had the idea of putting expansion chambers on a V6. After some searching, I saw it had already been tried with limited success, not making the HP/liter. I suspect that the reason is that the air flow is limited by having to go thru the crank/rod assembly to get into the transfers. Snowmobile engines get there air above the crank wheels. Arctic cat has figured out that tipping the cylinder away from the intake made for a mord direct flow into the bottom of the transfer tunnels increased torque. They call them laydown motors. If I didn't have anything else to do, I would like to build an outboard motor using the laydown engine platform. All outboards that I know of flow air thru the crank wheels which may required to produce the torque necessary to get a boat on plane. Just my observation.
-
Instigator liked this post
-
06-21-2020, 08:00 PM #154Screaming And Flying!
- Join Date
- Jun 2007
- Location
- Singapore/Melbourne/Italy
- Posts
- 9,097
- Thanks (Given)
- 1008
- Thanks (Received)
- 354
- Likes (Given)
- 4297
- Likes (Received)
- 1951
- Mentioned
- 7 Post(s)
- Tagged
- 0 Thread(s)
bore spacing is where an inline beats the Vee outboard, you just cant fit great porting into an outboard
-
Instigator liked this post
-
06-21-2020, 08:34 PM #155
Part of the questionable results of pipes on OBs is targeted RPM of the pipe.
An OB does not have a centrifugal clutch/transmission to keep the motor “on the pipe” like a sled.
In open class OB hydroplane racing they are allowed to run pipes/chambers and to make them work, they set them up to slide on the manifold, thereby adjusting their tuned length, allowing them to follow the power band.
Last I heard, the best 500’s were at about 150 hp’s or, 300 per liter.
Tuning, porting a two Stroke in an application w/no gear box changes everything.
Take your baddest sled and replace the clutch w/a sprocket and chain and see how it does.
I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.
I refuse to allow common sense to interfere w/my boat buying decisions.
Checkmate 16' 140 Johnson
Hydrostream 17' Vector FrankenRude I
Laser 480 (?) 21' w/GT 200
Glastron Carlson Conquest w/XP 2.6
Glastron Carlson CVX 20 w/XP 2.6
24' Sonic w/twin 250 Johnsons
24' Sonic w/twin 250 HO Johnsons
19' STV River Rocket w/FrankenRude II
Allison XR 2002 w/Frankenrude II
Hydrostream 18' V-King w/Frankenrude II
-
-
06-22-2020, 04:01 PM #156
And then give it a second maximum torque demand at 30% rpm (getting the boat over plane).
-
Instigator liked this post