I remove a SS 14x3/8 x 19 only going 3000 to 35000 rpm, I install a 14.8 x 17 aluminum it is a 15 spline prop 3 blade
Remember I am restoring this boat I have no base line to work with , Please see www.nymack66.com for some photo etc , I am stump in regards as to why the engine is not giving me the RPMs everyone is talking about !!

I would try a 15 pitch stainless wheel myself, but somethin don't sound right here. Are you sure your hitting on all cylinders under load? Is the timing set to 18 BTDC @ 5000 RPM's(very important that it is set at 5K as the power pack has about 4 degrees of advance in it with RPM due to trigger and stator outputs). Loopers are CRITICAL of timing. I would get you a bo0ok and go through the carbs top to bottom, make sure the plastic bodies are not warped. Then set the timing and go from there. To bad you aint closer, I'd help you figure it out as I'm fairly proficient with the V4 90 degree loopers.

Timing and link and sync was done by local dealer Boat Tune. I can only assumed it was done correctly
Carbs re-built inside out
Carburetor 397907 & 397908
Idle Air Bleed #28
High Speed #61D (I am not sure what he replace this jet with )
Intermediate #16

Those sound like the early 87 same as 86 carbs. These are the ones I am running. I'm jetted with 63D's main, 14's intermediate, and 34's(or 36's not 100% certain on which) for idle. This works excellent in mine running 50%1 pre-mix with PENNZOIL synthetic blend oil. But I have some very mild porting done in the exhaust ports behind the sleeves, and my air box has been slightly ported as well and I have a .020 over bore. I still trhink there is a problem with your link and sync or in the timing department. These engines are CRITICAL of timing. 2 degrees to much and meltdown happens, 2 degrees not enough and your 140 is a 115. THEY HAVE TO BE DEAD ON! I learned this one the hard way:cen:.

Update
 

Here is what installed
Idle=28
High=64D
Intermediate=Starboard side=16
Intermediate=Port Side=20
Note per the Parts Manual this odd sizes for the Intermediate is normal for this engine
I will test it on the lake hopefully on Sunday

Update2
 

I forget to mentioned I change the High Speed jets back to 61D per repair manual , I will test and post the results

Wrong lower unit you have a V6 lower unit none of the short shaft 20 inch motors had 15 spline lower units, they had 13 spline. Only the 25 inch 120/140 motors had 15 spline lower units. It could still be a 120 power head. My 120 and my 2 twin 140's both have 62D jets.

They did offer the bigger lower unit on 85 and some 86 140's, seen em with my own eyes. And I have 2 140 lower units that are both 13 spline V4 units. Your model number comes out to a 20" shaft, but you said before IIRC you said you have a 25" leg. Your carb numbers come out to an 86-early 87 140 carbs, but it could still have a 120 tuner and reeds which would give you a 130 I believe. I think you need to verify your tach, and then check your timing.

right ferm 13 spline but he said he has 15 spline that's either a 25 inch lower unit or a V6 which he has neither of. no 15 spline were on V4 motors with 20" shafts.

I've seen 2 of the 20" legs with the 15 spline shaft on the 140's. They both had the 2.25:1 ratio in them as well that came in the hybrid V6 leg. The reason I wonder about what he really has in his engine is he said he has a 25" leg and his engine number has the L not an X for a 20" leg. Sounds like some parts swapping has gone on with this here engine.