is a 65hp engine from 1976 equal to a 65hp engine from 2003?

[ShawnQ]

Just out of curiousity...<br /><br />If I would take a 65hp engine from 1976 in perfect running order, and a 65hp engine from 2003 in perfect running order, would they both perform the same?<br /><br />I would imagine that the newer engine would have a lot less parisitic loss between the engine itself and the prop, thus being more efficient (due to better technology, of course). I would also think that the newer engines are considerably lighter. However, I could again be wrong.<br /><br />I've seen newer boats the size of mine or larger (16+) with 40-50hp engines, and they would stomp a hole in my boat(65hp) even when it was running right. It could be simply due to hydro-dynamics, but I doubt it. Partially, but not fully because of the shape of the new boats.<br /><br />I ask because I am looking at possibly buying a new engine, and wondered if I could possibly shop for a little less power, and get the same result thanks to the light weight and better technology.<br /><br />Anyone?<br />Shawn

 

[totalivewire]

Re: is a 65hp engine from 1976 equal to a 65hp engine from 2003?

a horse is a horse. but im pretty sure you could tweak it up like you can a car.the weight of the motor, boat and passengers are what the horses are pushing. and then the prop size is important.the prop size is the problem if your engine is in good shape.

 

[Troy_from _Oz]

Re: is a 65hp engine from 1976 equal to a 65hp engine from 2003?

ShawnQ, <br /><br />From what I know of, I think that the 65hp of your 1976 engine was measured in a different way to the current models. Someone (more knowledgeable than me) will be able to clarify, but I think older engine hp was based on displacement (or measured at the crank???), whereas hp these days is measured ( or estimated) at the prop. If you search the forums youll find a few posts that estimate what the loss will be. you could then calculate the effective hp you have (on a good day) relative to current models. It might turn out to be something like being equivalent to 55-58hp in todays world???.<br /><br />I'd also think you might need to look at the power to weight ratio of your whole rig, rpms at WOT, gearbox ratios, prop selection etc. <br /><br />A boat that blows yours away getting out of the hole might only be set up for that - and may only have a low top end speed. It depends on what you want to use your boat for.<br /><br />Getting into the nitty-gritty, the width of the powerband or power curve would presumably also have an impact on how powerful the boat/motor feels.<br /><br />Just my ramblings for what they are worth.<br /><br />cheers<br />T

 

[JB]

Re: is a 65hp engine from 1976 equal to a 65hp engine from 2003?

In 1976, engine HP was rated at the crank. In 2003 it is rated at the prop, after any losses in the drive train.<br /><br />The 1976 engine probably produced between 55 and 60HP at the prop.<br /><br />Good luck.

 

[dkondelik]

Re: is a 65hp engine from 1976 equal to a 65hp engine from 2003?

Mornin' ShawnQ,<br /><br />JB and the others have "nailed" the HP rating thing (crank vs prop rating). I've been advised that as a rule of thumb, for pre '81 motors, subreact ~10% to estimate prop hp.<br /><br />Speaking of which, you may wish to evaluate your prop. This can make all of the difference in the world. If you can advise maxs speced operating operating RPM for your motor and detail on your boat (size,hull config etc.) some folks on this forum can direct you the the right size/pitch prop to help your ol' girl to really stand up and sing.<br /><br />But,...maybe,...just maybe,...<br />you should open this can of worms in a new thread (as this one is about hp ratings)