1987 Looper v4 140 RPM only 4000

[THEFERMANATOR]

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.

[Skools Out]

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.

[THEFERMANATOR]

Originally Posted by Skools Out

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.

[spareparts]

sound like a Frankenstien motor. I reember the 140 seadrives had the big lower unit, OMC ran a special on the motor assembly(every thing but the Seadrive bracket) for repowering an existing set up for a while back in the late 80s. They were selliing the motors for about what a new powerhead cost. We sold quite a few, just left the swivel bracket off the old engine, and put the seadrive stuff on, kept the standard OB cowl and lower covers

[nymack66]

Guys , lets face it maybe the lower unit was swap out for a v6 gearcase 15 spline , If this is the cause for my lack of RPM at WOT 4000 max then I have a lower unit from 1978 v4 140 I can bolt up to it , I brought this boat and engine from a guy that had about 20 plus motors, Who knows what he did or did not do. Please see nymack66.com page 2 and on I have photos of the engine , 140 is stamped on the block over by the throttle shift lever , I can bet it is a 140 due to the Pack, Sator, Trigger that was installed and is working. The stamp on the carbs as mentioned before is for a 140 . Could it be the gear ratio on the larger gear case be the cause ? Or should I just intall a 14x13 prop to offset the difference ?

[THEFERMANATOR]

I went back and looked at your pictures, that is definately NOT a 25" leg. It's a 20" leg, you can tell by the lower engine mount spacing. And it looks to be a V4 lower unit, not the hybrid unit that used a V6 prop. Have you counted the prop shaft splines? Or roughly what is the outer diameter of the prop hub? If it is a V4 lower, it is pretty much certain to be a 2:1 ratio which is proper for that engine. The 1.86:1 ratio in the V6 lower would KILL the V4 looper by taking it out of it's power band vs prop speed. Your prop sizes also sound like a V4 lower. I still think you need to try a 15 or 13 pitch prop. My 140 slings a 17 pitch to 46 MPH at 6100 RPM's, and a 19 pitch to 53 MPH at 5600 RPM's. It would spin a 15 pitch to around 5800 at 34 MPH on my old boat, wich would have been close to a V20 in weight.

What is your current WOT and speed at that RPM?

If your reaching 28 at 4000 RPM's your tach is pretty much dead on. 4000 with a 15% prop slip comes out to 27.4MPH. Sounds like the engine may not be tuned properly, or there is something amidst in the engine itself. You say you have 120-130 pounds of compression, have you checked this against another guage. I'm running 150-155 pounds in my 140 with a .020 over bore.

And all of the electronics are the same from 120 to the 140, no differences in between the 2 up through the 90's. The differences were internal. The numbers stamped on the block where you say is a casting stamp as I believ mine is stamped 138 there. Even if it has some 120 parts, it don't make a big difference. Both of them are torque monsters very well suited to a v I think. The problem being is these engines don't make much power up until around 3500 RPM's. If your overpropped and not letting the engine hit it's peak, it will be WAY off on RPM's. These engines are rated @5600 RPM's.

[nymack66]

My prop is a 15 spline for sure , I counted the splies on the shaft also,
My max RPM is 4000 , I will take it out with my GPS to clock the speed , I will post the results later