300Vti Runnung Issue help - loss of power

[Lang Mairne]

I am working on one that is throwing me for a loop.  My inability to talk tot he motor doesnt help.

Here's what we have done so far:

Impeller
Alternator
Fuel Pumps & Regulator
New Gas
Oil Change
Fuel Filter


Plugs are recent, shifts well and drive seems good. Battery tests good.

It takes off out of the hole at very first with what seems to be full power, then it quickly dives off to max out around 1000-1500 rpm and stays that way under a load.  Runs and sounds great on the hose though. 

It almost feels like an ignition issue that is not keeping up or not firing all the way, or some kind of safe mode.
Exhaust gasses are clean and it runs smooth at idle. I would like a good way to test the coils individually while its running. Can I hook up a basic spark checker with out hurting the electronics?

I am not familiar with these motors, but we are a service shop that works on most any other outboards and stern drives.

Does anyone have any "aha" type info for me or things to test the old fashioned way?

Thanks yall.  Your forums have saved me before...

[brad]

Try cleaning the flame arrestor filter and the MAF.

http://www.epicmarine.com/forum4/index.php?topic=2455.msg18853#msg18853

[wakejunky]

check for codes, see this post for directions

http://www.epicmarine.com/forum4/index.php?topic=2735.msg20397;topicseen#new

[Sammamish Skier]

Might be worth checking the fuel rail pressure. The shop manual in the maintenance section has instructions. My boat had a dodgy fuel pump before I bought it and it had issues with power.

[lesman01]

Any update on this? Did you get it running?

[jwilcox]

I also second the MAF and Spark Arrestor - made all the difference for me when mine was not running so well.