496 H.O. Prop size
10-08-2017 | 11:57 PM
#11
Banned
Joined: Jul 2011
Posts: 9,594
Likes: 45
From: Ft. Worth TX
I would like to see a scan(s) of the OP engine - overspeed will be shown A LOT.
The OP location is ? I could scan this
Max OEM Mercruiser straight from class and service manuals and owners manuals
375 hp 496 Mag 4400 to 4800 rpms
425 hp 496 HO 4600 to 5000 rpms
STOCK OEM and Stock PCM 555
The OP location is ? I could scan this
Max OEM Mercruiser straight from class and service manuals and owners manuals
375 hp 496 Mag 4400 to 4800 rpms
425 hp 496 HO 4600 to 5000 rpms
STOCK OEM and Stock PCM 555
Last edited by BUP; 10-09-2017 at 12:15 AM.
10-09-2017 | 12:13 AM
#12
Banned
Joined: Jul 2011
Posts: 9,594
Likes: 45
From: Ft. Worth TX
So you should not use the 555 in any race Applications. Rev limiter's act in milliseconds. I don't believe I'm going to ruin my motor with milliseconds on the limiter. And I truly believe it's better to hit the limiter once in a while then over prop it and strain the motor. At that rpm I doubt cylinder washdown would be a problem. The fuel would vaporize and get pushed out of the cylinder Way before it would wash. Just think how many times that piston goes up and down at 5400 RPM's
as for the video. He's talking about people that just stand on the throttle in neutral to make noise. Or drag racers that stand on the line for five seconds or more holding it on the limiter. I don't think he is talking bumping off the limiter now and then. Watch it again
as for the video. He's talking about people that just stand on the throttle in neutral to make noise. Or drag racers that stand on the line for five seconds or more holding it on the limiter. I don't think he is talking bumping off the limiter now and then. Watch it again
My posts as I wrote continuously and over time for rev limiting. I understand the once and while part of rev limiting because that's what it was intendant for ( protection ) . Also as I said if one left throttle(s) at WOT Rev limiting the Merc cal will go into overspeed then into overspeed 1 and overspeed 2. == Overspeed 2 limits engine power to 5 percent. Merc also knows the damaging effects if one just walled it to WOT and left it there rev limiting continuously never backing the throttles.
10-09-2017 | 12:21 AM
#13
Banned
Joined: Jul 2011
Posts: 9,594
Likes: 45
From: Ft. Worth TX
Possible tachs are off as well. A scan will also show TRUE rpms thru out all rpms. I totally recommend a scan to figure out true RPMs (scan tool rpms ) and if applicable OVERSPEED faults .
I have seen many tachs off 50 to 150 rpms is not uncommon for analog tachs. I have even seen some tachs off up to 400 rpms.
I have seen many tachs off 50 to 150 rpms is not uncommon for analog tachs. I have even seen some tachs off up to 400 rpms.
