aqad41a-dp290...best rpm range

[vince59]

well...after spending some time for checking that everything was ok last work was the water pump gasket...the boat was back in the water last saturday. We tested the boat in a short run and we had good performance up to 3500 rpm (we have a A7 propeller) and good sound form the old diesel 6cyl with 1300h life. Question...is there a specific range to keep to have the best performance? what is the upper rpm limit of these engines? with this amount of lifetime are the enginse to be considered old? very old? and as consequenca having poor performance?
I hope I made myself clear...english is not my mothertongue language

 

[Don S]

Re: aqad41a-dp290...best rpm range

You should be seeing 3700 to 3900 rpm. You are over propped and lugging the engine. Try some A6's lugging is a bad thing on those engines.

 

[vince59]

Re: aqad41a-dp290...best rpm range

Hi Don, can you give me some more details in simpler words...I am not sure about the word "lugging"..do you mean that this prop is not the original one for these engine? (we got the boat used).
What is the maximum rpm range for these engines?
Thanks

 

[Don S]

Re: aqad41a-dp290...best rpm range

"lugging" means overloading the engine, not allowing it to get to full rated rpm.

 

[vince59]

Re: aqad41a-dp290...best rpm range

Don I have to resume this thread for my better understanding. I can be now more precise I found a mixed combination of propellers on my boat equipped with aqad41a. We have an inner A7 3 blades combined with an outer A6 4 blades and this is not in accordance with volvo penta requirement. Despite that we tested the boat - not fully loaded - and we could read little bit over 3800 rpm and gps speed little bit more than 35kts. We are going to buy two new inner prop but so far we have big confusion about what to buy. Volvo guide indicates for a 147kw engine running 3700/3900 rpm and ratio 1.95:1 an A6 prop for max speed range from 34/37 and a A7 prop for a max speed range from 37/40. What is now your suggestion A6 or A7...thanks for your kind advice

 

[Don S]

Re: aqad41a-dp290...best rpm range

Forget the speed range, that's just an estimate. Find out which set A6, or A7 (not mixed) puts you in the proper rpm range. Speed will be what it is with the correct rpm.

 

[vince59]

Re: aqad41a-dp290...best rpm range

Don, following your suggestions and after reading a lot and talking to other guys I bought two A6 sets for my boat (shaft34).
I am now ready to install the propellers...before doing this I was wondering if is it a good idea having them painted with primer and antifouling paint in order to better protect the propellers.
What is your advice.

Thanks a lot

 

[Scott Danforth]

Re: aqad41a-dp290...best rpm range

make sure you grease the prop shafts before putting the props on. I would not paint the props with anti-fouling paint. then again, I trailer my boat

 

[vince59]

Re: aqad41a-dp290...best rpm range

make sure you grease the prop shafts before putting the props on. I would not paint the props with anti-fouling paint. then again, I trailer my boat

..you mean that you do not leave the boat inthe water?..in my case it is a must to leave it inthe water so I guess it is advisable to paint the propeller

 

[vince59]

Re: aqad41a-dp290...best rpm range

so any advice about painting brand new propellere with antifouling?