Originally Posted by chorscroft
I'm certainly going to look into chipping it. ....What sort of negative effects was codprawn talking about at high speed and how long would you have to run it at those rpms to do the damage?
Conor, to gain more performance this way the engines need to have some form of electronic diesel control and your pictures show the engines with cable control so the fuel system may be manual. However, there are 3 ways of doing it depending on the type of diesel injection system on the engine. They all rely on providing the engine with more diesel fuel and this works because diesel engines are normally run on an excess of air.
Firstly, on a common rail diesel it's possible to do it simply and for a few pennies by fitting a resistor into the fuel pressure sensor circuit. This fools the electronics into thinking the fuel pressure is a bit low so it increases the fuel rail pressure. The result is increased fuel injection pressure and therefore more fuel will be injected during the time the injectors are open.
Second, the chip route works by remapping the amount of fuel which the engine receives by rewriting the control program within the engine management system.
Third, and sometimes also known as chipping, is an add-on electronic device which intercepts the signals between the engine's electronic control unit (ECU) and the electronic control section of the diesel pump and it tricks the pump into delivering more fuel than the ECU has demanded.
Now, you can make use of the extra power in two ways. I'm going to presume your boat and engine are correctly set up at the moment.
Firstly, you can choose not to do anything about the boat set-up. The extra power will be available for improved load carrying, easier planing and generally better performance and throttle response. Also, this route is unlikely to stress the engine unduly because your extra power use is likely to be transient in nature and cruising will still require only the same power as the original set up. However, the engine will over-rev when at wide open throttle (wot) and you will need to take care not to do this.
The second option is to re-prop the engine until wot produces the correct maximum engine revs. This will give you the extra speed you are looking for but at the expense of extra stress on the engine. Also, the engine will be more stressed during cruising because you have over pitched your propellers in comparison to the original set-up and this will require you to open the throttle more to achieve the necessary power because the engine will be running more slowly at a given boat speed. This will probably put you outwith the manufacturer's duty rating for the engine. Do a Ribnet search for info regarding engine duty rating.
I hope this clarifies things a wee bit for you.
Edit: I forgot to say; trim tabs will be a good idea. They are unlikely to improve your top speed but they will give you an extra control option in a head sea and they can be used to control listing, which you will definitely have in a side wind.