Anyone mess with 377 marine SBC engines?
01-29-2007, 11:13 PM
#1
Anyone mess with 377 marine SBC engines? My dad has a Mercruiser 320hp fuel injected 377 in his boat that he's wanting to hop up. It is a roller cam small block with a 4.00" bore and 3.75" stroke, and 906 casting Vortec heads. Most marine parts are fairly expensive (exhaust manifolds start at $1200 and go up from there) so he was hoping to upgrade to a mild cam.
Unfortunately, he's pulled the motor and put a degree wheel on it to see what was in there, and it seems that the existing cam is fairly healthy. We expected to find something like a vortec truck cam or the RamJet cam. Instead, it looks like a 215/221 .454/.468 112+4. Sounds good, except thats about where we hoped to end up, so its a lot of work that doesn't leave much room for improvement.
Anyone else seen anything like this?
Unfortunately, he's pulled the motor and put a degree wheel on it to see what was in there, and it seems that the existing cam is fairly healthy. We expected to find something like a vortec truck cam or the RamJet cam. Instead, it looks like a 215/221 .454/.468 112+4. Sounds good, except thats about where we hoped to end up, so its a lot of work that doesn't leave much room for improvement.
Anyone else seen anything like this?
02-02-2007, 12:23 AM
#4
I guess what I'm asking is this - has anyone ever seen a similar cam factory installed in a marine engine?
The last boat he had came with the 300hp hydraulic cam. He switched to a cam 260H and ported the heads for some great gains. The better quality heads and cam make it tougher to gain ground.
The last boat he had came with the 300hp hydraulic cam. He switched to a cam 260H and ported the heads for some great gains. The better quality heads and cam make it tougher to gain ground.
02-02-2007, 10:53 AM
#5
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Merc made a Scorpion 377 SBC which was a little hotter than your Dad's 6.2L MX 377. The Scorpion came with a 222/230 .510/.528 cam. Can't remember if it was on a 112 or 114LSA. What type of boat? What outdrive? The main drawback of an I/O is selecting a cam that will allow idle free problems. Boats spend alot of time idling at low rpms in wake zones. You don't want a large low vac lumpy cam that makes docking a pain. I've been there done that with a large solid cam. It pulled like a **** to 6500rpms @ 78MPH GPS, but it would not idle and was a chore to keep running at low rpms. I was the only one who could drive the boat for this reason.
Also most boats aren't able to rev much over 5000 rpms so sticking in a large cam will do nothing for performance.
I'm currently building a new 355 SBC for my boat. I'm using a Comp grind very similar to the XM276HR, It's 224/230 .537/.510 112LSA 110ICL. I'm also running 10.0-1 SCR, with AFR 190cc heads. The setup is more race than the average boater would want but should still provide decent docking maneuvering.
Give me some more details on the boat, engine, rpms, setup and I might be able to help you a little more on the cam choice.
Good links.
Offshoreonly.com
Speedwake.com
hoatboat.net
boatingabc.com
Also most boats aren't able to rev much over 5000 rpms so sticking in a large cam will do nothing for performance.
I'm currently building a new 355 SBC for my boat. I'm using a Comp grind very similar to the XM276HR, It's 224/230 .537/.510 112LSA 110ICL. I'm also running 10.0-1 SCR, with AFR 190cc heads. The setup is more race than the average boater would want but should still provide decent docking maneuvering.
Give me some more details on the boat, engine, rpms, setup and I might be able to help you a little more on the cam choice.
Good links.
Offshoreonly.com
Speedwake.com
hoatboat.net
boatingabc.com
02-02-2007, 12:45 PM
#6
Ryan,
Thank you for your response. Sounds like you know your stuff, as reversion is one of our concerns. I don't think even the best manifolds on the market flow anywhere near a long tube header, and cam timing is a delicate balance.
The boat is a 2002 Caravelle Interceptor 232 (23') that probably weighs 3300-3500 lbs. It has a Bravo II I/O sterndrive with Captains Call exhaust. They use it as a runabout, but dad can be a speed freak so he'd like to eek out a few more mph. He's running a 23" prop that peaks about 5000, maybe 5100 when unloaded and 1/4 tank or less, at 60-62 mph.
We are looking at AFR Vortec 180 heads, which we'd likely mill to get the compression up to 9.5 since they are aluminium. Intake wise, I've never seen anything like the manifold that it has, and I don't know if it would be a major swap to get the Scorpion intake for an upgrade (mainly, all the electronics, sensors, brackets, etc). I've been looking at a Comp XFI Cam that spec out at 218/224 .575/.570 113 with 1.6 rockers. It's not much more duration, but .100" more lift can't hurt.
Would it be worth considering the upgrade to Scorpion specs?
Thank you for your response. Sounds like you know your stuff, as reversion is one of our concerns. I don't think even the best manifolds on the market flow anywhere near a long tube header, and cam timing is a delicate balance.
The boat is a 2002 Caravelle Interceptor 232 (23') that probably weighs 3300-3500 lbs. It has a Bravo II I/O sterndrive with Captains Call exhaust. They use it as a runabout, but dad can be a speed freak so he'd like to eek out a few more mph. He's running a 23" prop that peaks about 5000, maybe 5100 when unloaded and 1/4 tank or less, at 60-62 mph.
We are looking at AFR Vortec 180 heads, which we'd likely mill to get the compression up to 9.5 since they are aluminium. Intake wise, I've never seen anything like the manifold that it has, and I don't know if it would be a major swap to get the Scorpion intake for an upgrade (mainly, all the electronics, sensors, brackets, etc). I've been looking at a Comp XFI Cam that spec out at 218/224 .575/.570 113 with 1.6 rockers. It's not much more duration, but .100" more lift can't hurt.
Would it be worth considering the upgrade to Scorpion specs?
02-02-2007, 11:34 PM
#7
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No problem. Been around the boat scene for awhile now. Reversion is a concern on the stock manifolds and marine exhaust is very $$$$. For the price of manifold systems these days your best best if a set of Lightning headers if freshwater run. My Glenwood HP manifolds and Fastglass 4" short risers gave me 2mph on a stock Merc 5.7L 260hp.
Nice boat and it's always great to have a Bravo drive. I run a beefed up Alpha 1 with HD gears and have a spare just in case I break it.
The AFR SBC heads are awesome! I could not belive the performance increase I got with mine. I've ran 10-1 SCR on 89 octane on previous motors with no problems. Just watch the DCR. With a marine SBC stick around 7.6-8.0DCR. Anything higher and she will need 93 only and we all know how hard it can be to find that on the water. I wish I could offer more help on the EFI intake but I have no experience with it. I'm old school with carbs and timing lights lol.
The Comp XFI would be a nice grind that would fall right in line with the RPM the boat will see. Just watch PTV clearance with that lift. Degree it in for sure. If your going to step up to the Scorpion 222/230 which is simply a Crane 284HR grind then your probably going to have to drop some pitch to get the rpm up in the bigger cam's powerband.
The AFR's, XFI cam, marine exhaust with his current 23p prop should provide one heckuva increase and still be very civil in docking maneuvering.
Post a few questions on on the links to the forums I gave you. Very good group of people there willing to help. Also lotsa good searching.
Found you a few starters....
http://www.offshoreonly.com/forums/s...&highlight=377
http://www.offshoreonly.com/forums/s...&highlight=377
My previous 360ci SBC
My 1984 Hammond Challenger MKII V2150
Nice boat and it's always great to have a Bravo drive. I run a beefed up Alpha 1 with HD gears and have a spare just in case I break it.
The AFR SBC heads are awesome! I could not belive the performance increase I got with mine. I've ran 10-1 SCR on 89 octane on previous motors with no problems. Just watch the DCR. With a marine SBC stick around 7.6-8.0DCR. Anything higher and she will need 93 only and we all know how hard it can be to find that on the water. I wish I could offer more help on the EFI intake but I have no experience with it. I'm old school with carbs and timing lights lol.
The Comp XFI would be a nice grind that would fall right in line with the RPM the boat will see. Just watch PTV clearance with that lift. Degree it in for sure. If your going to step up to the Scorpion 222/230 which is simply a Crane 284HR grind then your probably going to have to drop some pitch to get the rpm up in the bigger cam's powerband.
The AFR's, XFI cam, marine exhaust with his current 23p prop should provide one heckuva increase and still be very civil in docking maneuvering.
Post a few questions on on the links to the forums I gave you. Very good group of people there willing to help. Also lotsa good searching.
Found you a few starters....
http://www.offshoreonly.com/forums/s...&highlight=377
http://www.offshoreonly.com/forums/s...&highlight=377
My previous 360ci SBC
My 1984 Hammond Challenger MKII V2150
Last edited by Ryan02SS; 02-02-2007 at 11:40 PM.
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02-03-2007, 12:00 PM
#8
Originally Posted by Ryan02SS
I wish I could offer more help on the EFI intake but I have no experience with it. I'm old school with carbs and timing lights lol.
Guess I'll be searching for other ways to tune, he's already thinking about just leaving it alone now. He's wishing he would have stayed with the carb'd 250 hp 5.7 now, as the $$$ to upgrade to this engine could easily have built a 406 or larger shortblock + nice heads and manifolds.
Thanks again for your info! I'll check out those links.
