Offshoreonly.com - need for speed

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just purchased 86 Formula 206 with a stock 5.7-260. Had her out yesterday and was only getting mid 40's out of her. Is this the norm? If not any suggestions?

Re: need for speed

In my experience, and based on rough computations, a properly running 20-footer with 260 hp should reach slightly over 50 mph.

In order to make a more accurate assessment of your situation, please provide more details, such as the size and type of propeller you are running, the drive gear ratio, the condition of the propeller, and the RPM's you are seeing at various speeds.

You can also go to http://www.speedboatperformance.com and run the online calculator there to see for yourself how your setup should be performing.

Sometimes, boats lose performance for strange reasons, such as water accumulation in compartments without proper or plugged drain holes, hull bottom warpage due to improper support on the trailer during storage. Your motor could be down on compression, or propeller could be dinged, causing it to cavitate excessively.

My investigation would begin by first analyzing the propeller selection. It is possible the previous owner threw on some cheap spare prop to sell the boat with. If you are overrevving at WOT, then most definitely you have a propeller change to make. If you are not making rated RPM at WOT, then there could be prop or motor trouble. Initial motor troubleshooting should consist of performing a compression check, checking spark plugs and wires, timing, and any obvious problems with carbuerator linkages. If all that checks out, it's time to check your fuel pressure, and then go through the carb to see if anythiing is plugged up.

At any rate, give some more info for folks on the forum to speculate with.

Re: need for speed

That sounds low to me. I don't know how heavy your boat is but I'd guess with a healthy motor and the right prop your boat should be running at least 55mph.

Re: need for speed

Quote:

Originally Posted by tcelano

In my experience, and based on rough computations, a properly running 20-footer with 260 hp should reach slightly over 50 mph.

I agree, you should be around 50, 55 when the moon and stars are aligned. :)

Re: need for speed

I have a chris craft 245 limited with a 260 in it and it runs 49.9 on gps at 4200 with a 21 P Mirage.Boat is supposed to weigh in at 3800 dry.
I will be building a better engine this winter for more MPH!!!