Like a kid waitin on Christmas

[Natural Light Kid]

I have an Optimax 225. Recommended max RPM is 5750. I'm trying a new prop and can turn it 6,000-6,200 RPM. From what I can tell, I'm still not hitting the rev limiter. I was curious if I was hurting the motor turning it up like that. The motor is 10 years old.

[Natural Light Kid]

Originally Posted by Natural Light Kid

I have an Optimax 225. Recommended max RPM is 5750. I'm trying a new prop and can turn it 6,000-6,200 RPM. From what I can tell, I'm still not hitting the rev limiter. I was curious if I was hurting the motor turning it up like that. The motor is 10 years old.

No response?

[CajunChristian]

Originally Posted by Natural Light Kid

No response?

QUOTE:
I can't speak for all motors. The tohatsu I raced was a stock motor with a rev limiter set at 5800 rpm, we could tack weld the crankshafts to keep them from spinning out of time. Recommended rpm for that motor was 5600, I spun mine up to 7400 rpm for extended periods of time. I ran the Parker Marathon. It is 40 laps of a 4.1 mile course with 1 mandatory 10 minute pit stop. That is 164 miles with one stop at 7400 rpm. The motor would drop down to abut 6500 in the turns then right back to 7400 for the 2 mile straightaway. Ran that motor an entire season with zero failures. On a short course, I would turn up to 7600 by the end of the straights. Most of our races were 1 hour testing on Saturday, 10 lap qualifying heat on Saturday, testing for 1 hour Sunday morning, 30 or 40 laps of a 1 3/8 mile course.
The Merc I just sold was a beast. The original powerhead ran for 10 years. The data showed that I hit the 6250 rev limiter over 400 times. That motor was turning 6200 everywhere I went. After 10 years and 2400 hours, it burned a valve.
The little 2 cylinder OMC 40/50 motors ran a class called sst45. That motor as a fishing motor was recommended to turn 5600, as an sst45, they turned 7200 rpm. They ran the Parker Marathon right alongside me.
I look at the recommended rpm as just that, a recommendation, not a rule.
I have yet to find an outboard that made peak power and torque at the factory recommended rpm. Sure, it might make 50hp at 5600, then it might make 60+hp at 7200.

[Natural Light Kid]

Originally Posted by CajunChristian

QUOTE:
I can't speak for all motors. The tohatsu I raced was a stock motor with a rev limiter set at 5800 rpm, we could tack weld the crankshafts to keep them from spinning out of time. Recommended rpm for that motor was 5600, I spun mine up to 7400 rpm for extended periods of time. I ran the Parker Marathon. It is 40 laps of a 4.1 mile course with 1 mandatory 10 minute pit stop. That is 164 miles with one stop at 7400 rpm. The motor would drop down to abut 6500 in the turns then right back to 7400 for the 2 mile straightaway. Ran that motor an entire season with zero failures. On a short course, I would turn up to 7600 by the end of the straights. Most of our races were 1 hour testing on Saturday, 10 lap qualifying heat on Saturday, testing for 1 hour Sunday morning, 30 or 40 laps of a 1 3/8 mile course.
The Merc I just sold was a beast. The original powerhead ran for 10 years. The data showed that I hit the 6250 rev limiter over 400 times. That motor was turning 6200 everywhere I went. After 10 years and 2400 hours, it burned a valve.
The little 2 cylinder OMC 40/50 motors ran a class called sst45. That motor as a fishing motor was recommended to turn 5600, as an sst45, they turned 7200 rpm. They ran the Parker Marathon right alongside me.
I look at the recommended rpm as just that, a recommendation, not a rule.
I have yet to find an outboard that made peak power and torque at the factory recommended rpm. Sure, it might make 50hp at 5600, then it might make 60+hp at 7200.

Haha. I gotcha. I guess I was trying to get you to say it was ok lol. Is it possible that I'm turning up those kind of numbers without hitting the rev limiter or could my tach be wrong?

[CajunChristian]

The tach could be off a bit, you'll know when you hit the rev limiter.

I had a 19' ProCraft, back when they were pad bottom bay boats, very fast hulls. I had a 200hp EFI Mariner/Mercury on it. The recommended rpm range was 5400-5600 rpm. I propped that motor to turn 6200 loaded, ran it for years until I sold it. Only problem I ever had was when it was 11 months old, the engine grenade, not a small problem. It stripped the nylon drive gear for the oil pump and all lubrication stopped. I was crossing Big Lake at 6200 rpm when a rod came through the side of the block. It was replaced under warranty and the complete oil system was removed. That failure had zero to do with rpm, the failure was caused by a lubrication part failure.
That old 2.0L V6 Mercury block is raced as an SST120. I built engines for a guy from Florida. His motors would turn 7200 rpm forever without fail. With good lubrication, proper jetting, sufficient cooling, they will run forever. And by good lubrication, we ran synthetic oils in the race motors simply because of the heat and rpm issue. The SST120 class is carbbed, so we played with jetting and timing, your EFI motor adjusts the air/fuel ratio and the ignition timing automatically. So you only have to worry about cooling and lubrication. That is why I would install a water pressure gauge and HAND mix the oil. I do not trust ANY oil injection systems.
D

[Natural Light Kid]

Originally Posted by CajunChristian

The tach could be off a bit, you'll know when you hit the rev limiter.

I had a 19' ProCraft, back when they were pad bottom bay boats, very fast hulls. I had a 200hp EFI Mariner/Mercury on it. The recommended rpm range was 5400-5600 rpm. I propped that motor to turn 6200 loaded, ran it for years until I sold it. Only problem I ever had was when it was 11 months old, the engine grenade, not a small problem. It stripped the nylon drive gear for the oil pump and all lubrication stopped. I was crossing Big Lake at 6200 rpm when a rod came through the side of the block. It was replaced under warranty and the complete oil system was removed. That failure had zero to do with rpm, the failure was caused by a lubrication part failure.
That old 2.0L V6 Mercury block is raced as an SST120. I built engines for a guy from Florida. His motors would turn 7200 rpm forever without fail. With good lubrication, proper jetting, sufficient cooling, they will run forever. And by good lubrication, we ran synthetic oils in the race motors simply because of the heat and rpm issue. The SST120 class is carbbed, so we played with jetting and timing, your EFI motor adjusts the air/fuel ratio and the ignition timing automatically. So you only have to worry about cooling and lubrication. That is why I would install a water pressure gauge and HAND mix the oil. I do not trust ANY oil injection systems.
D

Thanks. Great info. I do have a water pressure gauge. What kind of psi should I be pumping? Are those gauges pretty accurate/consistant?

[CajunChristian]

Originally Posted by Natural Light Kid

Thanks. Great info. I do have a water pressure gauge. What kind of psi should I be pumping? Are those gauges pretty accurate/consistant?

Even if the gauge is wrong, as long as it is consistent, it gives you something to base the pressure on. I use a 0-30 pound air pressure gauge.
If I remember correctly, my 200 would pump right at 27 pounds at 6200 rpm. If your gauge shows 25 pounds, just watch for any drop in pressure. If you go along for months reading 25 pounds then it suddenly drops 2-3 pounds, time for a look. Could be a worn impeller, could be a scratched housing. On you boat, I would not run for long if it drops to 10 pounds or less. I would rather be safe than buying a new block.
D