How can I tell if my engine is making the amount of power it should?

[marunr]

Re: How can I tell if my engine is making the amount of power it should?

I have a 1988 2.3liter. I run a 13-3/4 x 15 prop and WOT is about 5200. I can get 38 mph by myself and about 34 with 4 adults. With that prop I can get about 32 mph at 4600 rpms...the last few hundred rpms don't result in much of a speed increase, the prop is too small. With a 13-3/4 x 17 I can get a little more speed, but can't get above 4800 rpms so I think that's too much for my boat. I also have much better performance pulling skierws with the 15. I think it's the right size for that 2.3l OMC Cobra. (My boat is 17-1/2 feet)

If you truly have a 15 on there it sounds like an engine problem to me.

By the way, the number should be stamped on the prop hub when you look at the back, not on the side of the prop. Is that where you're looking?

 

[marunr]

Re: How can I tell if my engine is making the amount of power it should?

Yesterday we ran about 2-3 hrs wot

That's a lot of strain on a little motor. I've had mine since new for 20 years, and I rarely run at wot, and then only for a few minutes. I can run 28 to 30 mph with passengers and keep the rpms below redline (about 4300 to 4500)

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat

 

[marunr]

Re: How can I tell if my engine is making the amount of power it should?

I can't answer your prop question, you might try the prop forum. I only know that the prop I use is the size that came with the boat. The owners manual on that motor says wot should be 5200 to 5500. I don't understand why you can't hit 5200 with a 13 pitch prop unless something is wrong. I think there's something wrong with that prop personally, but the speed of 25 to 27 at 4200 with 6 people doesn't sound out of line. You should still have more power available. From what I gather reading the forums, the mechanics say you are lugging your engine (not good) if you can't hit wot. Maybe the previous owner got the numbers reversed when he bought the prop.

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat

 

[JoChek219]

Re: How can I tell if my engine is making the amount of power it should?

if you want 35mph... can always get a bigger motor there is no replacement for displacement!

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat

 

[JoChek219]

Re: How can I tell if my engine is making the amount of power it should?

you weren't asking about gas mileage.... you were talking about speed

Not sure if you'll get up to 40 with that motor but it can't hurt to try the props but when is the last time it was properly tuned up?

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat

 

[evilratgirl]

Re: How can I tell if my engine is making the amount of power it should?

Hey Kiwi, I have basically the same setup of the 2.3 cobra. First thing that seem amiss is the idea of a 15.5 diameter prop on this drive. If this is actually a 2.3 rated 13 spline drive, a 15.5 diameter isn't going to fit. The 2.3 and 3 liter drives are what are called small gearcase drives. The large gearcase drives for the 4.3 and above run 15 splines and diameters of 14+.

Of the compression specs you give, they look great. The picture of the crud around the waterline looks about right since ALL that weight is in the back.

As far as WOT, yes it should be at 5500 but not based on that kind of load. that kind of load. Someone did mention a varity of props for various uses. I also didn't see any mention of trimming the outdrive for best performance.

I also have to agree with the full tuneup needed. The 2.3 is alittle harder to fine parts for locally atleast around here. What I did find was twice the price I found on the internet including shipping. Iboats has been great but hasn't had everything. Of all my searching Boatfix has always had what I needed.

If an origional carb, get it rebuilt. Did mine this spring and what a difference. Also to get to the #4 plug you need to pull the riser, so make sure you get a gasket for it.

I love our 2.3. Not really the fastest, but it is really good on gas.

 

[kwikrnu]

Re: How can I tell if my engine is making the amount of power it should?

boat