Re: Merc 5.0 ignition
Hell yeah I need more horsepower! Who doesn't lol. It's just when I hit the factory limiter with the 19p prop I'm still picking up speed! There has got to be another mph or two left in this little 5.0 and alpha. I'm sure the cam doesn't just drop off at 4950........
Yes it does!! You know that once you reach maximum power (4600rpm on these engines) any increase in revs, because of a lack of load (in the marine business we call the prop a load), is also a REDUCTION in horsepower. Just have a look at any power and torque graph for any engine (with the exception of a rotary, they're crazy!).
So, as EVERYBODY has already told you, use an increase in propeller pitch to get the engine speed down.
To demonstrate. I run a 17" prop and hit the rev limiter at 5100, that's about 39 knots. When I change to a 19" I have max revs of 4600, and a top speed of 43.2 knots..... I get over 4 knots increase with just a prop change, NOTHING else. (I run the 17" 99% of the time because I like the better response in the mid-range....)
Here's the thing about boats. You could easily build a SBC engine that makes 400hp, peaks at 6,500 rpm, but it would be undriveable. Boats need engines that produce TORQUE at the low end of the rev range. That's incompatible with an engine that make huge horsepower at the top end (generally). If you want more speed, then get a prop on there that gets the engine to turn in the top half of the RECOMMENDED REV RANGE, which in your case is 4600-4800. And don't think an ali prop is the answer. They're blades are too thick and flex too much, you need a good SS, like a Laser II or a Mirage. Even a Vengance is better than Ali....
Just my 0.02....
