torque ratingon mercruiser

[hudman]

anyone know the torque rating on a mercruiser 5.7 260 hp,,, non vortec, carb motor? 2 bbl. cant seem to find it from mercruiser, or in the owners manual<br />thanks,,<br />hud

 

[Don S]

Re: torque ratingon mercruiser

None of the Mercruiser (or Volvo for that matter) Marine gas engines have torque specs posted for them.

 

[ron7000]

Re: torque ratingon mercruiser

5.7L<br />

<br /><br />4.3L<br />

<br /><br />3.0L<br />

 

[Don S]

Re: torque ratingon mercruiser

Those are not the torque specs for his PRE Vortec engine, those are for the new engines.

 

[QC]

Re: torque ratingon mercruiser

Originally posted by Don S:<br /> None of the Mercruiser (or Volvo for that matter) Marine gas engines have torque specs posted for them.

Any guesses why? Because peak torque is borderline meaningless on a marine engine despite popular opinion. Prop load curves never approach peak torque because they are a fixed load that rises relatively linear to RPM. The only time that a Marine engine gets close to peak torque is if the throttle is hammered AND the boat struggles a little to plane. If the boat as is "jumps" onto plane then peak torque again doesn't really matter. If the boat struggles to plane, then an engine with better peak torque value will help it "climb out" a little faster.<br /><br />It is important to note that I am talking about "peak" torque which is what hudman asked about. Marine engines are indeed operating "on the torque curve" at one other point: WOT RPM. That is where power required crosses over with power available, and the engine is then at it's max output for that specific RPM. If propped properly this point is nowhere near "peak" torque capability or peak torque RPM.<br /><br />So the ultimate question for hudman is why do you want to know?

 

[hudman]

Re: torque ratingon mercruiser

ive been told that torque moves a boat, and i need to move mine<br />Actually, ive got a 260 hp mercruiser 5.7 that is locked up, pretty sure it dropped a valve. going to replace it with a vortec 350 with a aftermarket fuel injection system. curious on if there will be any noticable improvement in power, but the old engine probably wasnt up to par, so the new one should perform a lot better... ill keep you posted on results

 

[QC]

Re: torque ratingon mercruiser

hudman,<br /><br />In someways torque moves everything, but reality is that the combination of torque and RPM result in horsepower and that's what moves your boat. Another fact . . . if you buy more horsepower your boat will go faster . . . It is that simple. Yes, an engine with a higher torque rating will possibly help a boat get on plane faster and yank a skier out of the water faster, however if their max rated horsepower is the same, the boat will go no faster at top speed. So IMHO what you really want to concentrate on is the horsepower rating, especially if you are going with the same displacement i.e. 5.7L (350 CID) . . . Good luck!!

 

[180shabah]

Re: torque ratingon mercruiser

Just FYI peak torque on a pre Vortec 5.7 should be around 340.

 

[TilliamWe]

Re: torque ratingon mercruiser

Originally posted by hudman:<br /> ive been told that torque moves a boat, and i need to move mine<br />Actually, ive got a 260 hp mercruiser 5.7 that is locked up, pretty sure it dropped a valve. going to replace it with a vortec 350 with a aftermarket fuel injection system. curious on if there will be any noticable improvement in power, but the old engine probably wasnt up to par, so the new one should perform a lot better... ill keep you posted on results

Diagnosis aside, you should notice a difference between your current 260 and the replacement engine, if you get the fuel injection working properly and the motor runs properly. But the difference isn't going to feel like you bolted a 502 in there.

 

[murphini]

Re: torque ratingon mercruiser

Sorry to "thread jump" here, but question I have is does anyone have an idea for the torque curve of a marine Ford 5.0 (302 V8) with 2bbl? I would assume it's between the Chevy 4.3V6 and the Chevy 5.7 V8, so roughly in the 300ft/lbs range...

 

[QC]

Re: torque ratingon mercruiser

murphini,<br /><br />I believe that your assumption is reasonably correct. If you look at the curves above they have about a lb ft. per cubic inch. They are probably a little better per cube than what I assume is an older engine coupled with that 2 bbl . . .

 

[murphini]

Re: torque ratingon mercruiser

THanks. All I know is that it was satisfying experience to demonstrate (respectfully of course) the principal of torque to my Dad this past summer. His first time on my boat (20' 305 V8), he had been in outboard powered boats in the mid 70's, and hadn't really ridden in a boat for a few decades.<br /><br />He was standing up in the back of the boat to take a picture of my daughter before I hit it to get her up on the wakeboard. I said, "You may want to sit down", He said, "I'll be OK". I said "You may want to brace yourself when I mash the throttle, it accelerates pretty quick", he said, "I'll be OK" and sort of bent his knees. I said "You Sure?", he said "hit it". I said, "Ok, here it comes"... It was semi-comical seeing his body lurch when I hit it, his knee was braced on the bench seat so he was able to stay upright, but he was clearly not expecting the force of the acceleration. He turned and smiled at me and said "Wow". <br />That helped him understand what 300 (?) ft/lbs of torque felt like. I let him drive later and it was role reversal to when I was 16 learning to drive our Ford LTD with the 400 4BBL in it. My foot didn't quite get the concept of gradual acceleration.

 

[QC]

Re: torque ratingon mercruiser

murphini,<br /><br />Just remember one thing. You are capable of delivering 300 lb/ft torque It is the rate at which you deliver that torque that ultimately matters i.e. bhp (bhp=torquexRPM/5252)

 

[JasonB]

Re: torque ratingon mercruiser

Murph, I think the stock torque was 280'ish. I don't have that as a hard written number, but I seem to remember reading that somewhere. There seem to be quite a few uf us still out here running 302's