Loss of rpm (and power?) on 150 Evinrude Intruder 1997

[JanW]

Hi
New to this forum, greetings from Finland. I recently got a 1997 150 (E150ILEUC, serial G04295094) intruder with a broken ignition module (450h on the engine). The module was fixed at DFi and now i got the engine out for a few testruns.

The engine starts fine and runs smootlhy but doesn't give me more than 4900 rpm and the speed is only 31knots. A friend has a identical engine and boat (Buster Magnum), he gets 41knots at 5400rpm. Tested with different props, no big impact on speed or rpm.

The engine gives a water in fuel error on a regular basis, haven't found any logic in when it happens. Randomly best describes it. I've changed the fuel filters, the water in fuel sensor and emptied the fuel tank. It's seem that the EMM "can't let go of the erros"? One technician here said the error could be related to the tachometer. Any views on that?

I don't think the rpm and the water in fuel errors are related, two seperat problems?

Planning to do a de-carb this weekend if i can find some stuff similar to sea foam here

Thoughts?

Regards
Jan