rslifkin
Guru
- Joined
- Aug 20, 2019
- Messages
- 7,931
- Location
- USA
- Vessel Name
- Hour Glass
- Vessel Make
- Chris Craft 381 Catalina
Generally for most engines I stick to a guideline of no more than 40 - 50% throttle, and no more than 40 - 50% of max RPM until full coolant temp. Then 50 - 60% is acceptable for a few minutes until the oil gets up to temp, then go for it. This guideline applies to cars, boats, etc.
For engines without a temp gauge, it's a bit different. The boat generator gets 2 - 3 minutes of un-loaded warm up, then apply load. Keep the load below 50% for another few minutes while it finishes warming up. Dinghy outboard gets a minute or so before departing if it's cold (hasn't run in a few hours), then keep it under 3000 RPM for a minute or 2 after departing. It's a small engine, so it warms up fairly quickly.
Long, slow warmups at idle with no load aren't good for any engine, as it spends a long time running in a sub-optimal state. Better to raise the idle a couple hundred RPM until you're ready to go (gets combustion temps up a bit and gets better oiling to the valvetrain, cylinder walls, etc.).
I usually bring my engines to ~1100 at startup. Being gassers, they usually creep up to ~1200 after a minute or so as the chokes start to open. They'll creep a bit further if left to warm up more, but by the 1 - 2 minute mark we're usually throttled back to idle and departing the dock (or pulling up the anchor). For comparison, normal idle when fully warm is just over 800 in neutral, ~700 in gear (a little under if in gear tied to the dock, just over 700 when moving). Idle is a little lower (50 RPM or so) when cold.
For engines without a temp gauge, it's a bit different. The boat generator gets 2 - 3 minutes of un-loaded warm up, then apply load. Keep the load below 50% for another few minutes while it finishes warming up. Dinghy outboard gets a minute or so before departing if it's cold (hasn't run in a few hours), then keep it under 3000 RPM for a minute or 2 after departing. It's a small engine, so it warms up fairly quickly.
Long, slow warmups at idle with no load aren't good for any engine, as it spends a long time running in a sub-optimal state. Better to raise the idle a couple hundred RPM until you're ready to go (gets combustion temps up a bit and gets better oiling to the valvetrain, cylinder walls, etc.).
I usually bring my engines to ~1100 at startup. Being gassers, they usually creep up to ~1200 after a minute or so as the chokes start to open. They'll creep a bit further if left to warm up more, but by the 1 - 2 minute mark we're usually throttled back to idle and departing the dock (or pulling up the anchor). For comparison, normal idle when fully warm is just over 800 in neutral, ~700 in gear (a little under if in gear tied to the dock, just over 700 when moving). Idle is a little lower (50 RPM or so) when cold.