Did you measure speed with a gps ?
Some water pick up speedometers are easy off 10% .
I was assuming your 300xs is having 1,62:1 ?
that is the heaviest ratio merc has ,it could be stamped into the lower unit.
The Cyclone with the 300 xs turns a 27 or a 28 pitch and runs 84 mph.
Make sure the pitch is right ,maybe they put a 27 or 29 into the box at mercury.
How does it accelerate? if its a 23 pitch it should be neckswapping.
With a 27 or 29 (29 is the biggest mirage)accelerating out of the hole is still good but not neckswapping.
Without any slip at all, the sums say 80.66mph, so nearly 88mph would be a bit of a miracle, a 7mph miracle. I think that if the RPMs, and pitch are correct, sterling is right on the money at 73mph, but agree there's a good chance that either, or both of the critical factors (pitch & RPM) are wrong, coz it should go pretty kwik!
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"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
Did you measure speed with a gps ?
Some water pick up speedometers are easy off 10% .
I was assuming your 300xs is having 1,62:1 ?
that is the heaviest ratio merc has ,it could be stamped into the lower unit.
The Cyclone with the 300 xs turns a 27 or a 28 pitch and runs 84 mph.
Make sure the pitch is right ,maybe they put a 27 or 29 into the box at mercury.
How does it accelerate? if its a 23 pitch it should be neckswapping.
With a 27 or 29 (29 is the biggest mirage)accelerating out of the hole is still good but not neckswapping.
sterling
It was at a Gps indeed and indeed it is a 1.62:1 box , i will check the prop tomorow .
She is out of the water in notime and a lot quicker than my 18ft Phantom you sow winter 2006 .
thinkin about it it must have been a bigger pitch! my 24 pitch @ 6000rpm was only at 68mph?
Thats about 9% slip still its very good to have such low slip,efficiency is great.
But some boats run their fastest speeds with 14-16 % slip ,in the end its no big deal how much slip there is ,as long as the speeds are tophigh.
I run my cat with 16 % slip,and reach my highest speed with that .
I think its fairly high ,but whatever I did to try its going to run slower.
so I have to live with it I guess.
Whent out with the Seaquel this weekend , the gps that gave me a 141km/h earlier proved to be incorrect , the new readings with a 23p Vensura (cup hase been changed to ???) gives me 133km/h @6100rpm , here is a movie that one of our dutch forum-members made this weekend :
Still the same ,no slip at all ?you should do normally 118 km/u or 74,2 mph with 10 % slip calculated.
I would check it again if pitch is right ,or if your rpm gauge is doing a good job.
check rpm with a Snap on timing tool ,some tools have a 2 stroke setting ,just multiply by six ,just to check your rpm gauge.
I would say you have to swing a 26 or 27 pitch with that boat.
Try one and see if you can reach 6100-6300 rpm,that should bring you to 84 mph.
I didn,t look at the video ,but let someone next to you hold the gps tight,let him or her watch the gps numbers going up as you drive the boat,the numbers have to go up in steps like 65 mph 68-69 -71 -74 78 -80 some sudden movements will bring gps numbers to a higher speed levels,and if recalls the highest speed it can show 70-71 -73 -84 as a movement by a impact from a bigger swell .
Let well ,I have no doubt your combo will run those speeds,but the small prop is a strange thing.
Whent out with the Seaquel this weekend , the gps that gave me a 141km/h earlier proved to be incorrect , the new readings with a 23p Vensura (cup hase been changed to ???) gives me 133km/h @6100rpm , here is a movie that one of our dutch forum-members made this weekend :
Still the same ,no slip at all ?you should do normally 118 km/u or 74,2 mph with 10 % slip calculated.
I would check it again if pitch is right ,or if your rpm gauge is doing a good job.
check rpm with a Snap on timing tool ,some tools have a 2 stroke setting ,just multiply by six ,just to check your rpm gauge.
I would say you have to swing a 26 or 27 pitch with that boat.
Try one and see if you can reach 6100-6300 rpm,that should bring you to 84 mph.
I didn,t look at the video ,but let someone next to you hold the gps tight,let him or her watch the gps numbers going up as you drive the boat,the numbers have to go up in steps like 65 mph 68-69 -71 -74 78 -80 some sudden movements will bring gps numbers to a higher speed levels,and if recalls the highest speed it can show 70-71 -73 -84 as a movement by a impact from a bigger swell .
Let well ,I have no doubt your combo will run those speeds,but the small prop is a strange thing.
cheers Sterling
Arthuur she is hooked on a SC5000 Smartcraft so the rpm is correct , like i said befor , the prop i am running right now is cupped , to what pitch i do not know .
I am having doubts about the lower unit if it realy is a 1.62:1 , but the numbers are there and you are more than welcome to drive along and look at the numbers the gps shows (last run i had 3 on board wich gave the same nummbers)
If you want to check out your lower unit ,thats easy .
If yours is a 1,62:1 ,you have to turn the crankshaft 1,62 turn and the propshaft will turn 1 revolution.
You can use your flywheel to find the 1,62 ,I have a 360 degree timing disc that I use but you can take a measure tape and measure the outer diameter from the flywheel ,lets say its 100 cm ,than 62 cm should be the 62 you need .
take a point on the engine near the flywheel and mark it ,and start turning from there
As I said i have no doubt your boat will run 133 km,my friend s Cyclone with 300xs does that also.
Strange that some modified cupping increases so many in pitch,usually they add cupping for extra bow lifting ,this may affect the actual pitch,but usually not by 4 inch,but hey nothing is impossible.
I will try that this week to see if it realy is a 1.62:1 and will take a picture of the cupped and a original prop , the cup is realy much bigger than the original one .
I also curious to see were the speed is comming from accutualy ....
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