speed problem

octo · 04 May 2006, 16:42

hi guys took the boat out for a spin today and noticed that we weren't getting above 30mph on the boat site a diagram says that with the engine we got it should hit around 40 mph so i wondered i any one knows what the problem could be
engine: 50 hp evinrude e-tec
thanks in advance

ps: no extra weight in the boat just 2 persons

Tideway · 04 May 2006, 17:03

depneds what they define as light! Try x1 v.small person, light fuel, wind & tide behind you and an optomistic GPS...

codprawn · 04 May 2006, 17:03

Have you had the boat go faster before or is this the first time you have used it?

What revs are you hitting?

Have you tried trimming the engine up or out more?

Also try moving the passengers around in the boat - further forawrd to get on the plane easier - then as far back as possible for higher speed.

Finally if the boat has been in the water without being used for a month or so it xould be weed or slime on the hull.

ADS · 04 May 2006, 17:10

With a 50HP ou should see 35mph, or 30 knots, 40mph is abit optimistic maybe 36/37mph as a one off but proabably 35mph as an average in regular use. Is the engine run in yet, and are you trimming it out.

Biggles · 04 May 2006, 17:16

What Boat is it on ? Is the boat a heavy boat. Whats the hull shape etc.

octo · 04 May 2006, 17:22

we have had it in the water before and it reached same speed with different trim settings same load.
it was a second hand boat (grand g480gl) and engine combi from the dealer so the engine was run in combi from 2002 i think.
max revs is around 6000
i personally think it's something with the tacho that the sensor isnt far enough in the water or something could this be the problem?

codprawn · 04 May 2006, 17:33

You have to use GPS to get an accurate speed - tacho measures engine revs - it is the speedometer that uses water pressure.

If you are hitting 6,000 rpm it is right on the top limit - you could propbaly change your prop and get a better top speed.

ashbypower · 04 May 2006, 17:45

As codders said GPS is best, remember the speedo probe in water measures speed through the water not speed over ground.

Brian

octo · 04 May 2006, 18:10

thanks guys i'll try and get some read outs of an gps next time