1996 merc 175 EFI stutters at WOT and only reached 4300 rpms! help

hello all!
New to this forum!

HERE is my problems! ah

I have a 1996 175 merc EFI, I have a 23p trophy prop, 4 blade. it just came from the shop, new plugs, new fuel filter. I just replaced my thermostats as my pee was not the strongest, seemed to clear that up. but I do have hot water coming out pee hole ( for the older mercs, I read that the stats do not open up until 143F so you can expect hot water)<is this true to anyone that has knowledge in the area?

Second:
so my hole shot is excellent and take off is excellent, to plane is great. the problem occurs when I try to push my hot foot down to the floor to get me to top end, it will run at 4300rpms and sputter(miss? and best I can describe it is like a " buuuuuubumpbuuuuubumpbuuuubump") when pushed all the way to the max. my Engine is suppose to be max 5000-5600 rpms. so I am not sure why it will not reach its potential. I know a 4 blade will slow your RPMS, but by 1000 rpms, I find hard to believe. after running on plane for a bit, I will go to shut it down and then restart it 2 minutes later and it will start up and run for about 2-5 seconds and die, it will do this 2 or 3 times then start up and idle fine, or I throttle it a little and it will start up. it had Oil injection pump, but it is now straight full pump and I mix. I recently started using Quick silver premium plus 2 stroke oil vs. the previous owner had used the quick silver 2-stroke oil? has a red label? I also added some sta-bil as well which the previous owner said he never did and strictly run 87 gas. he fished 3 to 4 times a week.


im not sure when my coil packs where changed last, thought that could be a problem, my compression runs cylinders 1-3 are 95 and 4-6 are 90, I will check again this week sometime? I pulled the spark plug and they DO NOT look new, the look like they have been in there for a while and its been ran twice?

so my questions are

what could cause my "miss" at WOT?
And why are my RPMS so low?

any help is greatly appreciated!!!

please help me break down these problems!!!

thanks fellas/ladies

Welcome to BBC!

Please see the Announcements at the top of the forum, and add the REQUIRED info to your post. Thanks!

Start by checking the BASICS:

-Visual inspection
-Compression Test
-Spark Test
-Fuel Quality, Delivery, and Pressure/Pressure Leakdown Tests

Better than 90% of all performance problems are found somewhere in the above basic tests. :thumb up2:

BTW... is this 23P Trophy a very recent addition?