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-   -   Max RPM on a 330 merc? (https://www.offshoreonly.com/forums/general-q/187850-max-rpm-330-merc.html)

JimmyBaja 06-01-2008 04:44 PM


Originally Posted by Griff (Post 2575923)
425 hrs is nothing for a 330. Spin it up to 4600-4800. It won't make hardly anymore power past that point.

Griff, I am only turning up to 4200. You think it's safe to turn 4600?

MOBILEMERCMAN 06-01-2008 05:06 PM

You actually put more of a load on the motor dragging it down to 4200 or 4400. You are probably in the secondaries at 3200 or 3400. At 5000 k your not in the secondaries till later maybe 3600. You can cruise at 75% throttle at 4000 or 4200 endlessly.

Having bigger motors is nice but they don't live near as long. we would burn the belts off and add gas. Pretty good boating.

socalstone 06-01-2008 05:16 PM

I have a 454 started life as a 330. Have about 300 hours on it now.
Spins 4800 all day long in my jetboat. I changed the heads, cam, intake, and exhaust about 5 years ago. That really livened it up. Could probably handle 4900 or 5000 now but will need a shorter impeller. It's a workhorse and 4800 seems very safe (especially for non-forged internals), so I'll leave it like this til the motor wears out or lets go.

I think it's a good motor with the right cam, heads, and exhaust.
When it's rebuild time, you can pick up an easy 100hp with a few simple changes.

Enjoy!

MOBILEMERCMAN 06-01-2008 05:47 PM

4800 is a good number. Most 330's that fail that I've seen is a result of a leaky exhaust like a riser gaskets. I suggest you change them every few seasons don't wait for them to begin to weep. Its cheap and easy to do.

Griff 06-01-2008 06:14 PM


Originally Posted by JimmyBaja (Post 2576278)
Griff, I am only turning up to 4200. You think it's safe to turn 4600?

Easily. Like was said, you're actually lugging the engine some. dropping down 2" in pitch or a good prop lab job will get you there.

rssteiny 06-01-2008 06:23 PM

i would lab the props your spinning and get the rs up to 4600-4800 and you will also go faster.:D

Knot 4 Me 06-02-2008 01:33 PM

Got a buddy running stock '96 330 bottom ends with Brodix heads, roller cams, Merlin intakes, 4150 Holley's, MSD inginition, and CMI e-tops. Runs them 5K with no problems. Probably would not want to spin them much faster for any length of time.

Pat McPherson 06-03-2008 01:52 PM

Prop for 4600rpm with a normal load; then you'll be at 4800 real light or 4400 real heavy.
The engine will not make more power above 4600.

diggster69 06-04-2008 11:11 AM

Thanks for all the opinions its running about 4500-4600 rpm and just wanted to be safe.
Chris

ECeptor 06-04-2008 04:41 PM


Originally Posted by Pat McPherson (Post 2578489)
Prop for 4600rpm with a normal load; then you'll be at 4800 real light or 4400 real heavy.
The engine will not make more power above 4600.


That is exactly what I've done with mine. I tried 4 props before I found the one (Revolution 4b 21p) that put me in that sweet spot.


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