I do believe I got bit by my purchase...
05-29-2017, 12:49 PM
#82
Platinum Member
Platinum Member
I stopped reading on page 7. Dunno where all you went from there but here are some thoughts.Correction - I jumped ahead to the end.
A Mercruiser 454Mag or 454/330 would last about 5 times longer than the 244 hours that are on the boat. Wonder why the motor swap..
A 502 crate motor would likely be in the 450hp range.
450 hp would spin your [email protected] prop well past 5500rpm.
No GM crate 502 with stock heads and stock compression is going to make 527/570 thru Merc V6 exhaust elbows.
No stock headed 502 with stock compression is going to make 527/570 with a cam that prevents exhaust reversion at low speeds.
You want a reliable motor - you are going the right direction.
Open up exhaust restrictions.
The cam you selected has a little more exhaust duration than you need (230/112) so you DO need to keep an eye on reversion. Not sure I would have recommended it, but if its not reverting water it will work fine. Install it 4 degrees advanced. Check for reversion (chop the throttle from planing speeds, drop off plane to full idle speed/stop, kill motor immediately - check plugs for evidence of water).
Your intake and carb are perfectly fine for your goals.
Set total timing advance to 34 degrees, let initial fall wherever your distributor and box have it.
Adjust idle mix AFTER timing is set as described.
Take care of your oiling issues, make sure the engine is in balance, adjust motor mounts for proper drive alignment, should be good to go for freshwater.
Prop the motor to rev to 4800 with typical load, but not over 5000 with lightest load. You don't have enough cam to warrant operation past 5000 max. You may see best "lightly loaded" top speed when propped for 4850-4900 just you, a splash of fuel, light chop, with the wind, trimmed for best speed.
If you plan to run in salt, there are 50 more things you need to consider.
A Mercruiser 454Mag or 454/330 would last about 5 times longer than the 244 hours that are on the boat. Wonder why the motor swap..
A 502 crate motor would likely be in the 450hp range.
450 hp would spin your [email protected] prop well past 5500rpm.
No GM crate 502 with stock heads and stock compression is going to make 527/570 thru Merc V6 exhaust elbows.
No stock headed 502 with stock compression is going to make 527/570 with a cam that prevents exhaust reversion at low speeds.
You want a reliable motor - you are going the right direction.
Open up exhaust restrictions.
The cam you selected has a little more exhaust duration than you need (230/112) so you DO need to keep an eye on reversion. Not sure I would have recommended it, but if its not reverting water it will work fine. Install it 4 degrees advanced. Check for reversion (chop the throttle from planing speeds, drop off plane to full idle speed/stop, kill motor immediately - check plugs for evidence of water).
Your intake and carb are perfectly fine for your goals.
Set total timing advance to 34 degrees, let initial fall wherever your distributor and box have it.
Adjust idle mix AFTER timing is set as described.
Take care of your oiling issues, make sure the engine is in balance, adjust motor mounts for proper drive alignment, should be good to go for freshwater.
Prop the motor to rev to 4800 with typical load, but not over 5000 with lightest load. You don't have enough cam to warrant operation past 5000 max. You may see best "lightly loaded" top speed when propped for 4850-4900 just you, a splash of fuel, light chop, with the wind, trimmed for best speed.
If you plan to run in salt, there are 50 more things you need to consider.
Last edited by mcollinstn; 05-29-2017 at 12:54 PM.
05-30-2017, 07:38 AM
#83
Had a good run on the lake this weekend and it's really running good. The new Bravo One 22p prop still gets me in the low/mid 50's at a 4600 rpm range in the noisy mode (70 gallons of fuel and the boss). Few hundred rpm less through the prop. It does miss miss a bit in the low 4K range but not WOT. Does not seem to break up through the prop though. Is there a mandatory rpm the the Captains Call should be used?
When cold the oil pressure is still up in the 60-65 psi range (cold) but only peaks in the 45-50 range when oil is up to temp. I'm reading about 240 degrees at the filter in the now 65 degree lake.
I ended up pulling a quart of oil out before launching. I hate that plastic rod dipstick as I struggle reading oil level with it being so glossy. I'd like to modify it to read better.
When cold the oil pressure is still up in the 60-65 psi range (cold) but only peaks in the 45-50 range when oil is up to temp. I'm reading about 240 degrees at the filter in the now 65 degree lake.
I ended up pulling a quart of oil out before launching. I hate that plastic rod dipstick as I struggle reading oil level with it being so glossy. I'd like to modify it to read better.
05-31-2017, 04:31 AM
#84
In case you missed it.
Do not run your boat with a full load of fuel/people until you get the "miss" fixed.
I run my Corsa closed when coming into and leaving the harbor. Open (through transom) everywhere else.
Your cold oil pressure is acceptable.
Your hot oil pressure is acceptable.
Is the 240 degrees at the filter before the cooler? I hope so. I would like to see it a little lower.
...It does miss miss a bit in the low 4K range but not WOT
...Is there a mandatory rpm the the Captains Call should be used?
...When cold the oil pressure is still up in the 60-65 psi range...
...but only peaks in the 45-50 range when oil is up to temp...
...I'm reading about 240 degrees at the filter in the now 65 degree lake...
...Is there a mandatory rpm the the Captains Call should be used?
...When cold the oil pressure is still up in the 60-65 psi range...
...but only peaks in the 45-50 range when oil is up to temp...
...I'm reading about 240 degrees at the filter in the now 65 degree lake...
I run my Corsa closed when coming into and leaving the harbor. Open (through transom) everywhere else.
Your cold oil pressure is acceptable.
Your hot oil pressure is acceptable.
Is the 240 degrees at the filter before the cooler? I hope so. I would like to see it a little lower.
05-31-2017, 07:46 AM
#85
No, the boat did not get run on a stand. The engine shop just set up
all non-marine long block...the boat shop set up all the marine stuff. Initial run (assuming on a hose) did have a vac leak prior to carb rebuild...The boat shop's mechanic said it runs great but I'm sure not at 4K.
Although I now know not to run exhaust through the prop above 2500-3000 rpm...I did it. There was NO 4K miss through the prop...only with the exhaust through transom. Made me think my Corsa diverters were rattling BUT I could feel it kinda holding back. It did not "miss" at WOT either position. When idling around the dock I did notice some through transom exhaust like the diverter was not closed fully. Not positive this is new or I just noticed the little blow by (exits under swim platform)...but yes it was a bit louder. Hope I didn't f it up switching at higher rpm. Embarrassing.
The oil temp is read right at the remote oil filter location...before the 215 degree Improved Racing oil thermostat...which directs the hot oil through the cooler...which is a mercruiser cooler shown to be on mercruiser 502's. No I don't have a post cooler reading.
The fuel in the boat (1/2 left over from last October/ and 1/2 fresh this past weekend) is/was 91 octane no ethanol from a new (last fall) station. Gas was treated last fall with Merc's treatment.
My engine builder had mentioned to me (when I picked up the long block) that he would prefer to log A/F ratios in the boat and adjust carb accordingly. Maybe that's the next step?
Thanks for your time. Dave
all non-marine long block...the boat shop set up all the marine stuff. Initial run (assuming on a hose) did have a vac leak prior to carb rebuild...The boat shop's mechanic said it runs great but I'm sure not at 4K.
Although I now know not to run exhaust through the prop above 2500-3000 rpm...I did it. There was NO 4K miss through the prop...only with the exhaust through transom. Made me think my Corsa diverters were rattling BUT I could feel it kinda holding back. It did not "miss" at WOT either position. When idling around the dock I did notice some through transom exhaust like the diverter was not closed fully. Not positive this is new or I just noticed the little blow by (exits under swim platform)...but yes it was a bit louder. Hope I didn't f it up switching at higher rpm. Embarrassing.
The oil temp is read right at the remote oil filter location...before the 215 degree Improved Racing oil thermostat...which directs the hot oil through the cooler...which is a mercruiser cooler shown to be on mercruiser 502's. No I don't have a post cooler reading.
The fuel in the boat (1/2 left over from last October/ and 1/2 fresh this past weekend) is/was 91 octane no ethanol from a new (last fall) station. Gas was treated last fall with Merc's treatment.
My engine builder had mentioned to me (when I picked up the long block) that he would prefer to log A/F ratios in the boat and adjust carb accordingly. Maybe that's the next step?
Thanks for your time. Dave
Last edited by 92cobalt243; 05-31-2017 at 08:10 AM.
05-31-2017, 10:18 AM
#86
Run the fuel that your engine was built to run. This is why you should know and/or post the engine's build sheet.
If the engine is like a stock Mercury 502 Mag then don't run premium gas.
A final tune in the boat is always a good thing.
If the engine is like a stock Mercury 502 Mag then don't run premium gas.
A final tune in the boat is always a good thing.
05-31-2017, 11:08 AM
#87
I agree about knowing the original build...you know I've tried. What I do know is the Chevrolet Performance 502HO Crate motor specs out 92 octane premium. I did find out it has Mahl pistons but don't know if they were what Chevy used (?). Still think 87 octane should be used?
05-31-2017, 12:45 PM
#89
Talk to me about 30 degrees total timing for the crate motor specs vs. I believe 34 total per ThunderBolt IV recommendation. Which rules?
05-31-2017, 02:39 PM
#90
Registered
iTrader: (1)
There are more people buying crate motors for the street than for marine. So there are more ding dongs by shear #'s on the street than the water. So, they are covering their azz. More unerhood heat, higher coolant temps...etc,etc will add to this too.
I know many people that can knock down a barn by just looking at it.
I know many people that can knock down a barn by just looking at it.
