Low transmission pressure

Selector Valve scratches

What the factory calls normal

The control-valve spring changed too: current black springs run 115-135 psi in neutral, forward and reverse at 500 rpm on a V-drive; older white springs run about 25 psi lower, 90-120 at the same rpm. That's the white-painted spring Chris found below, and why swapping it for a black one raised the pressure back up.

There's no separate tap for the forward clutch: in forward, line pressure is clutch pressure, so a pressure drop from neutral to forward usually means a forward-clutch leak. Gauges run 0-200 or 0-300 psi on a 71C/72C; on a 5000 or Liberty, 0-100 psi at the main port and 0-500 at the clutch taps, since a 0-300 gauge can peg on a 5000 in gear.

What Chris sees on the bench

• Scratches on the selector valve. One transmission came in with no pressure, and the scratches on the selector valve were the issue. That one was a quick fix. If honing the bore doesn't clean it up, that's a replacement-transmission situation, since the valve alone won't solve it.
• A rusted plunger. Sometimes if you get water in a transmission, the plunger gets rusted in on the bottom and it won't give you the pressure you need.
• The wrong spring. On one unit that had water in it, the selector valve had an old spring with white paint on it, going back to the 80s. On the test stand the pressure stayed the same in reverse, neutral and forward, so Chris knew the problem was probably the selector valve. We put in a black spring. On a 1014-005 CR-2, a new selector-valve spring took the pressure from around 100-110 psi up to 150.
• Cross-feeding. A rebuilt 71C looked fine at first. After we ran it for about an hour, forward pressure started dropping, and fluid was cross-feeding across the entire selector valve.
• Other causes worth ruling out: the wrong-weight oil, a blocked oil-inlet screen or shield, or a pump that's indexed for the wrong rotation. Any of those can show up as low pressure in both forward and reverse.

Velvet Drive Selector Valve white Spring

1014-005 Velvet Drive Cr-2 tested

May 11, 2026

Fix and prevention

Pull the selector valve and check it for scratches, and check the plunger for rust. Hone out a scratched bore and put in a replacement selector valve; if the bore won't clean up, it's time for a replacement transmission. When you reinstall the valve, here's a tip: line it up with the bolt on the bottom. That gives you neutral, so the ball lines right up and you don't have to fiddle with it and fight it when you put it all together.

On 5000-series units, if you find the old collared springs, they need to be replaced with the updated springs.

And don't judge a rebuild on a quick test. That cross-feed only showed up after about an hour, and that's why we run these transmissions as long as we do.

One more thing on low rpm: if you're doing a lot of trolling or idling, you're not getting a whole bunch of lubrication through the transmission.

Never run a 71C or 72C without a cooler or a bypass tube hooked up. The pressure regulator relies on cooler flow, and without it, line pressure goes too high instead of too low.

In our experience, forward needs the most pressure to hold, so it's usually the first thing to act up when something's starting to leak internally, before reverse shows any sign of trouble.

When to call

If your transmission is showing low pressure, call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com.

Related reading: creeping neutral and selector valve problems and how we rebuild a transmission.