Max safe rpm for testing prop

[Streffpilot]

Hi, iv got a 1972 or 1973 (always mix it up) Mercury 1150 with direct charge and thunderbolt ignition.

Here's the story: I have a prop on it now, but it allows the motor to rev past the 5300 rpm redline. So according to the gurus on the prop section of this forum, I need max gps speed and max rpm to get the right numbers to get a better prop. The problem is, iv had it up past 5700 rpm and there is still some throttle left to go. Do I just go for balls to the walls max and hope it doesn't wreck anything, or what other options do I have?

Thanks in advance for the assistance.

 

[Bondo]

Re: Max safe rpm for testing prop

Hi, iv got a 1972 or 1973 (always mix it up) Mercury 1150 with direct charge and thunderbolt ignition.

Here's the story: I have a prop on it now, but it allows the motor to rev past the 5300 rpm redline. So according to the gurus on the prop section of this forum, I need max gps speed and max rpm to get the right numbers to get a better prop. The problem is, iv had it up past 5700 rpm and there is still some throttle left to go. Do I just go for balls to the walls max and hope it doesn't wreck anything, or what other options do I have?

Thanks in advance for the assistance.

Ayuh,.... Start with a Bigger prop, so's it Don't over-rev,...

 

[Streffpilot]

Re: Max safe rpm for testing prop

Problem is, somebody (who shall remain nameless) backed the old prop into the garage door. the old one is about 4" higher pitch and 1 less blade than the current 17" 4 blade. Any ideas what the cost is to have a prop fixed, and new hub put in? I bent the tip of a blade, and it has a small crack now.

 

[Bob_VT]

Re: Max safe rpm for testing prop

Ahhh..... the older inline Mercs lover to rev up and really run!

Here is a quote from one of the BEST inline people I know who rebuilds them for a living........ his name is Clams_canino

[h=2]"Some Free Tips![/h][h=2][/h]Let's keep it alive BEFORE you need me. Detonation kills any motor. To avoid detonation and destruction, please observe the following:
1) Timing: REGARDLESS of the factory stickers, set the max advance ignition timing (at cranking speed) to no more than 21 degrees before TDC.
2) Fuel: Don't use "economy" grade fuel. You don't have to use "super premium", but don't run the cheap stuff - midgrade is fine.
3: Prop: Prop the motor so that it can make at least 5800rpm at WOT. Don't make it "lug". Though propped to 5800 you should run it at no more than 5500 for daily use. They cruise nicest at about 4200."