Hello. Thank you for reading my post haha well me and my dad have a first gen 6bt cunnings 250 in our bay and off shore fishing boat. The motor is 100% stock appart from a k and n filter from Autozone. Were are only able to push 22 knots wide open and we should be able to get more then that. We have got the right wheel under her just wondering what all we can do to the motor starting with cheap then high dollar things. I think because its a boat motor the exhaust is already like 5" or more. The turbo is internaly waste gate. And re fuel pump is a rotory pump. Please let us know what we can do and where we can get the parts + part numbers and price if possible much thanks mat and mick

 

So are you asking for help on the Dodge or the boat?

 

How many RPMs are you at at wot? How big is the boat? 22 knots sounds good for a big boat...Mark

 

Guys I removed one post because it was nothing but an insult due to an unfortunate typo...... Typos can be funny at times but the OP here did NOT intend to do it and there is absolutely NO reason to insult him over a simple mistake. If you can't offer any real advice then just stay out of the thread.

 

Look in the sticky and there is alot of info there on how to turn up a ve pump. Just becareful because the egt will go up a lot in a boat because there is a lot of load on the engine. How big is the boat and how heavy is it?

 

Yeah, I'd think you'd want to get a good set of gauges before you do anything. After that, you can probably just tune up the pump just like we do on the trucks.

 

Its a 25 ft bertram she should be going closer to 30 knots wide open although it is a heavy boat. My rpms. At wide open are 2700.

 

I don't know much about diesels in boats, but maybe pop the top off the fuel pump and install the 3200 rpm spring. That might get you a few more RPMs and hence a little more speed.

Either that or its a prop issue..?

 

When you say you "have got the right wheel under her" do you mean you believe the prop is the correct size and pitch? I know that on my simple little outboard that different prop pitchs make a world of difference in speed and performance. Like others have said gauges first, then note what your operating EGT's are. With the torque that the cummins has, you might be able use a more agressive prop but you would need to know what your WOT EGT's are to decide. Maybe you could barrow a different prop to see? I don't know much about vessels your size but could be a thought. Just my 2 cents worth. Good luck!

 

Are you sure that you have the correct wheel? Was it the stock from the factory? I know from my 20' outboard that the pitch makes plenty of difference in launch and top speed, I am sure that you know this already. I get about 29 knots top speed with mine, but it is probably a much lighter boat...Mark


Ahhh yorel, you beat me to it, I need to type faster

 

wouldn't the top speed be relative to prop size as compared to the weight of the boat and then after that prop rpm? then from there directly relating to that, engine rpm?

I wouldn't think the boat would necessarily need more power. More RPM or a bigger/more aggressive pitch prop to push it along would be my guess. then from there maybe more power if it's struggling to gain speed further.

am I right in that thought?

 

yup, I think that the 6bt has enough torque to spin a block of wood. He either needs a different prop or more RPM's...Mark

 

Its a trial and error thing... you keep pitching up your prop until you can't get your full rpm. At that point you either need to step down a pitch, or add more fuel. Might be a Lucas pump in there instead of a VE.

A friend of mine has about a 26' bertram also, but with a 3208 cat. (turbo, but HEAVY). I don't think he gets 22 knots even.

 

You very well may have a Lucas pump. I doubt it has an AFC housing being a marine engine. Also, being a 250hp marine engine, I bet it already has a 3200rpm spring if it is a VE engine (I think the VE Marine engine was 230hp). A picture of the pump up close with a camera in Macro mode would really help us identify it. If it's VE, most articles on this sight will help. If it's a Lucas pump, some fellows on here or boat sites might be able to help.

I would certainly get an EGT gauge to make sure you are not overloading the engine and melt a piston. Most likely a heavier spring, or clipping a turn off the current RPM spring and checking your full throttle stop on your levers and pump will help. After that, there are more adjustments, but things will get hot.

A boats engine load is like a truck's going uphill all day long. Things heat up quicker.

Do you have a SW intercooler? Air intercooler?

-Luke

 

If it has a 3200 RPM max and you're prop is getting you to 2700, you're definitely in need of a different prop!