2004 Nissan 40 TLDI NSD40B

My motor will start,idle, and rev up fine on muffs out of water, but runs pretty bad in a body of water. It bogs down and some times stalls when given throttle and can take up to 5-7 seconds for the boat to start moving. Most of the time I have to start at half throttle on my tiller handle to get the boat moving and when i get it up on plan it seems underpowered. I have replaced my battery with a 1000 MCA which would be fine in my warmer climate, New plugs, and fresh gas. I do not have a tachometer to run diagnostic on my motor and am trying to get answers before going to a dealer as they can be expensive. I know these motors are not typically backyard mechanic serviceable, but i’m looking for anything that could possibly be causing this issue.

Definitely need a tach and need to check air and fuel pressures to diagnose.

pvanv said:

Definitely need a tach and need to check air and fuel pressures to diagnose.

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Where might I get one?

Any dealer.