my 2004 larson sei (I/O Merc 3.0 135) is stalling out when running between 1200 and 2400 rpm's. It doesn't make much sense to me. It will run at head speed of about 1000 rpm's and at good speed over 2600 rpm's but not it the middle?? I'm clueless. I thought it might be bad gas but I get my...