We purchased our boat in Dec of 2023. Back in April we had been boasting for about 3hrs with a mixture of cruising and idling. When we went to get up on plain we couldn’t get past 10 knots. We ended up getting into a harbour for the night. We checked fuel, transmission and engine fluids. All good. Had a diver check underwater and all good. Next day went to head home and the boat got up on plain with no issues for the next 3 days.

Fast forward to yesterday and we were boating from Victoria to Seattle and were 2hrs into the cruise when the starboard engine powered down. When ended up doing 10 knots to Seattle. The starboard engine would not idle below 1400 or go above 1800. It appears that the throttle is adjusting properly as I played with it on the engine but could not improve on the RPM.

Fuel filters are new in Oct 2023 and have less then 20hrs on them. The mechanic that has worked on the boat the last 10yrs is stumped on what the cause could be.

To add to this. When we ran both engines to get the boat at 10knots. The swim platform was 2” under water. When we ran only the port engine with the boat at 10 knots. The swim platform was 2-4” above the water line.

The boat has the Twin Cummins 5.9-BTA Diamond Series 330 HP diesels

I tried to get a mechanic to look at the boat today with no success. I have some mechanical skills when I have direction on what I should be looking for. I am thinking it may be a linkage issue between the bridge and engine. Does not seem like a fuel supply issue but could be wrong on that. I did check the shut offs in the engine room incase one had shaken closed a bit.

Any thoughts or advice are much appreciated. Thanks in advice.