wilful Posted February 7, 2012 Report Share Posted February 7, 2012 I am looking at buying a quicksilver 640 pilothouse and test drove one abroad over the weekend. It is nearly unused and has a 115hp mariner 4 stroke efi on the transom with a 17 inch prop. It stopped revving at 4200rpm which seems shy to me. Is this too much for this setup or is there a more serious problem? I know there are a good few of these in the club so would be interested to know what is working on the prop setup and whether there is anything I should be looking out for please.. Wilful, my beloved 28ft bertram flybridge moored at Tuckton bridge, Christchurch is still for sale due to a buyer who had no money !! I will let her go to a club member only at Quote Link to comment Share on other sites More sharing options...
Rob Posted February 7, 2012 Report Share Posted February 7, 2012 Does it rev freely up to max revs (6000 i guess) when not in gear? Of course if 17" is the right one - then the engine is perhaps under performing, all cylinders firing etc? Rob Quote Link to comment Share on other sites More sharing options...
Coddy Posted February 7, 2012 Report Share Posted February 7, 2012 Gordon There has been a few threads on WSF of this engines on the 640 regarding props and if I recall most seem to go well on a 16" prop but not sure of the pitch. If stainless steel I think the 17" worked best but they had to tweak the pitch. So much depends on the amount of weight on the boat including people!. Dave Quote Link to comment Share on other sites More sharing options...
duncan Posted February 7, 2012 Report Share Posted February 7, 2012 Dave, Surely 16 and 17" are the pitch? - it's unlikely that you will get alternative diameters for such OB engines. Generally, beyond the pitch you tend to move to number of blades and related profiles for OBs. Also conventional theory has it that the alloy prop is less efficient at higher revs, through flexing, and that a 16 SS would equate to a 17" alloy (rather than the other way round). Personally I'm not convinced that this is actually what happens in practice but that's another issue! However, back to the original post, 4200 is simply miles away from the working WOT for that engine. If my memory serves me it's high 5's to mid 6's so there's about 2000rpm 'missing'. Obvious questions would revolve around what hull speed was being achieved at 4200? This would give a quick indication of whether this is simply massively overpropped in the mistaken belief that this improves fuel economy (it doesn't), overloaded, or other issues. Quote Link to comment Share on other sites More sharing options...
Maverick Martin Posted February 7, 2012 Report Share Posted February 7, 2012 The following stats are lifted from the Mercury website (Same engine as the Mariner) and from that you can see the engine should rev somewhere between 5800 and 6400. If it were mine I would be worried about over stressing the engine components. I would want this engine to rev at a minimum of 6000 revs before I felt happy. At 4200 it isn't giving anything like what it should. It either needs a major re-prop or something is amiss with the engine Martin HP/Kw @ Prop 115 / 86 Full throttle RPM 5800-6400 Cylinder Configuration 4 (in-line) Displacement (CID / CC) 105.7 / 1732 Bore and Stroke (in / mm) 3.23 x 3.23in 82 x 82mm Fuel Induction System 4 valves per cylinder, dual overhead cam (DOHC) Ignition ECM 07 Digital Inductive Fuel System Electronic Fuel Injection (EFI) Alternator Amp 50 amp / 630 watt Recommended Oil Mercury 4-Stroke Outboard Oil Recommended Fuel 87 octane/up to 10% ethanol Shaft Length 20 in (508 mm) 25 in (635mm) Dry Weight * Lightest model available 399lbs / 181kg Quote Link to comment Share on other sites More sharing options...
gaffa Posted February 7, 2012 Report Share Posted February 7, 2012 Got to concur with Duncans comments re the pitch. I have a Mariner 115hp efi on my Ryds 600AC and the Stainless steel Mercury Vengence prop is 13 inch with a part no. 48-16986-16P that is 16p is the pitch. Can't really say what max revs it will pull but if I open her up I can guarantee its above 5400rpm Hope this info helps Peteg Quote Link to comment Share on other sites More sharing options...
Coddy Posted February 7, 2012 Report Share Posted February 7, 2012 Opps! Duncan you are totaly correct Must think more before I type, sorry my mistake Senior moments getting more common Who am I again? Dave Quote Link to comment Share on other sites More sharing options...
Brian Posted February 8, 2012 Report Share Posted February 8, 2012 Hi Gordon I've just spoken to Dave, aka "Pirky", who has the same boat (Alice ll) and engine. He's happy for you to phone him regarding prop and revs etc. I've sent you an email with his phone numbers. Quote Link to comment Share on other sites More sharing options...
wilful Posted February 8, 2012 Author Report Share Posted February 8, 2012 Some very useful information, Thank you. I think we may have hit on the potential problem. The vendor tells me it is running on a 17" alloy prop 13" dia. He has ran it so few times he says he wasn't aware it could rev more either empty or laden. The guys from the local Mercury/Mariner dealer are going to give it the once over for me just in case there is a cylinder down, but I doubt it as it is purring sweetly (not a missed beat). I have put in a call to Dave , Brian and we are going to go over the stats for the different uses and see if it concurs with the revs expected from a 17" pitch prop. Having fished the Arvor 215 in Norway, I must say I am rather taken by the QS640 and if the way they hold value is anything to go by, they are sought after. Is there anything I should be aware of specific to these boats? Cheers Gordon Quote Link to comment Share on other sites More sharing options...
Maverick Martin Posted February 8, 2012 Report Share Posted February 8, 2012 They are good value boats for the money but from what I have heard things do tend to fall off so expect minor repairs on a regular basis. The clue is in the first seven words of this post as boats and value for money are not bed mates. All that said look after it and it will look after you. Martin Quote Link to comment Share on other sites More sharing options...
pirky Posted February 9, 2012 Report Share Posted February 9, 2012 (edited) Gordon....... I have the Mercury Vengeance SS prop on mine 48-16986 -16p ...... 16 " pitch .... 13.125" dia ..... revs fine and does 26-28 kn...Two up and over half a tank of fuel ...on a flat sea !! Have a look at the Mercury prop selector here props I played for hours !!! different loading, uses and expectation/economy etc ..... I think if you start going off shore more the pitch went down to 15" and the dia went up to 13.25" Came to the conclusion that for the variety of use and loads that I will use .... the prop I have on is ok !! Call me if you want more of a chat Dave Edited February 9, 2012 by pirky Quote Link to comment Share on other sites More sharing options...
lady jane Posted February 9, 2012 Report Share Posted February 9, 2012 seems strange that if you have a 16 stainless that equates to a 17 ally, so what are your max revs ? just interested. andy Quote Link to comment Share on other sites More sharing options...
pirky Posted February 10, 2012 Report Share Posted February 10, 2012 Andy .... If that was directed at me I have always chickened out on pushing her right out because of swell or she seems to take off !! ..... but I have had it up around 5800 revs ..... typically ..... recorded the other Sunday... good conditions .....solo with just over half a tank and little other load ( ie little in way of tackle etc ) .... 3000 ...9 knots 3800....16 4000....18 4500....23 5500....27 fuel consumption ... not accurate but about the usual litre/nm Have done the 26 + knots with 2 up and tackle though( weight well forward)...again in flatter conditions !!! I do not have trim tabs ....and I am not sure if this would improve drastically with them installed ??? Works for me .... Dave Quote Link to comment Share on other sites More sharing options...
lady jane Posted February 10, 2012 Report Share Posted February 10, 2012 dave, thanks for that. andy Quote Link to comment Share on other sites More sharing options...
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