low rpm at WOT while in gear

[freeflight2]

This afternoon our 2000 310DA with V-Drives gave us some trouble on the starboard side. As we throttled up to cruising speed the starboard engine RPM maxed out at 3000rpm before the boat even came up on plane. We could advance both throttles, and the port side would continue to increase the rpms, but the starboard side would stay between 2800-3000 rpm no matter how far forward we pushed the throttle. We throttled back and shifted to nuetral, and both engines would throttle up just fine to 4000-5000rpm. When we put it back in gear and tried to slowly throttle both back up, the starboard wouldn't go any higher than 3000rpm. The boat still couldn't get on plane and our max speed was about 10 knots. We had the nose trimmed fully down but it still would get on plane. Any thoughts? Thanks

 

[Lazy Daze]

Are there any obstructions, like rope, wrapped around the starboard drive shaft/propeller? How cold is the water down there?:smt001

 

[freeflight2]

Are there any obstructions, like rope, wrapped around the starboard drive shaft/propeller? How cold is the water down there?:smt001

Got under the boat today and both props spin freely with no fouling of props or shaft. Suppose it could be a fuel supply issue under load. At 3000 rpm, advancing the throttle doesn't continue to increase the rpm when in gear.

 

[Jimmy Buoy]

Had a similar issue last summer. Turned out to be one bad plug that didn't show until the engine was under load.:huh:

Replace your plugs lately?

 

[Southpaw II]

Change the plugs, first. Before I changed mine last year, the first sign I saw was that one engine would not rev as high as the other without a lot more throttle. Then , it slowly got worse until I changed plugs. That's all it needed.

Don

 

[Lazy Daze]

If there are no obstructions, I'd agree with the above posts that the next step would be the ignition components. How about cap/rotor/wires for good measure? Have they ever been changed? Might be a good idea to perform this on both engines if it's been a while, regardless.

 

[Air O'Nautical]

I agree tune-up and see...
If no better check compression.
Good Luck,

 

[flflatrate]

if your a mechanic you can go out and just have that motor running in gear at about 1400rpm. get the plastic pliers and pull each wire off your cap one at a time and see if the rpm drops. If it doesn't you know its not running on that cylinder. Then go from there. I also saw if you have vapor lock kits on there and that pump isn't woking it will slow the engine down to around that rpm also.