I need to increase rpm

[diego17a]

I need help to increase the rpm of my engine I have a dynamite .32 the spec.say the output for the engine is 28000 rpm the engine is only runing at 14216 rpm, how or what I need to do? the boat is a thundercat 31 the prop is pranther 215 stock I change the prop to a bigger pich pranther 225.but it is the same. :confused:

[BoatDoc]

is the engine broke in all the way yet? it may be a matter of needle settings. maybe stepping down to a smaller prop would help too. if it has a pipe, you could play with pipe settings also.

[Fluid]

How are you measuring the rpm now? If you are measuring it on the shore, that is the wrong way. The motor will unload considerably once it starts moving and the rpm will increase. Just because the advert says it will run at 28,000 rpm does not mean that is the best ropm for the motor.

The advice that BoatDoc gave is good, the prop is too big, go back to the original factory prop. Also, many motors will still be too tight after running a quart of fuel through them; be sure the motor is fully breoken in. Be careful when leaning out the needle, set it too lean and the motor will die easily out on the pond....usually out in the middle! :(

[BoatDoc]

usually in the middle...thats theONLY place they die :eek: it would be good to know how you're measuring RPM also. if everything else is OK, it could be a strut depth/angle thing too.

[mjmsprt40]

Use a smaller prop. I can't speak "for sure" about the 215, but the 225 is a size I use on .40 and .45 size engines. It's too much prop for a .32 and will load it up.

[diego17a]

the way I calculated the the rpm is by using this http://www.props4u.com/prop_chart.htm I put all the info speed 31mph, prop slip% 20, pich inch 2.8, gear ratio 1. I want at lease to go at 22000 rpm. :(

[CG Bob]

That calculator works several different ways. Plugging in 22,000 rpm; gear ratio 1; 20% prop slip; and 31 mph says that the prop pitch will be 1.86. You need a smaller prop with less pitch.