dodgy speedo ?.what speed shhould i expect from my boat /engine set up

[anna]

just finished renovating an old 16.5 ft stebber craft boat, it is fiberglass with a clinker style planning hull weighing about 400 kilos. the speedo pick up was broken at the back and i think i kinda fixed it but not sure .when i blow down the tube it registers on the dial.the boat has a 1978 115 hp mercury engine running good.when i took it out for trials i took it up to around 4500 rpm and it only registered just over 30 mph ,the engine has more in it and i would be gratefull for any advice as to what i can expect speed wise as i cannot trust the speedo

 

[BaileysBoat]

Re: dodgy speedo ?.what speed shhould i expect from my boat /engine set up

Try a GPS

 

[tashasdaddy]

Re: dodgy speedo ?.what speed shhould i expect from my boat /engine set up

you need a new pitot, also these are not totally accurate, you need to get the motor set up for the optimum wot rpms, rather than speed.

 

[anna]

Re: dodgy speedo ?.what speed shhould i expect from my boat /engine set up

thanks for the replies, my question was prompted from another thread where someone had a 17ft boat with a 200 hp eng which he said reached 74 mph which replies confirmed the eng and set up was near spot on. i was hoping someone with a simmilar set to mine with a good speedo could let me know what their speedo read at max revs i only took my eng up to 4500 rpm for trial ...bill