prop for 85 evinrude

[helfertyc1972]

I have a 1969 85 Hp Evinrude. Its tuned well and runs fine. Its mounted on a 18 ft crestliner, 1974 model, deep v, approx 1000 lbs weight. its a big water, deep draft boat. Right now I am running about 30 mph, trimmed up with one aboard, at 4600 rpm. I think its running a little hot as powerhead is hot to touch and pee hole water is hot. Am I right that this motor should be turning approx 5-5500 rpm. I cannot determine what prop is on motor now, there are no markings in hub or anywhere. Any suggestions for a good start on this motor as to what prop to pick? I think i should drop the pitch about 4 inches to increase revs by 800 rpm, don't know where to start though. Any suggestions appreciated.

 

[ledgefinder]

Re: prop for 85 evinrude

Since you have to try one to get a read on the rpms, my guess would be 15" pitch. 17" pitch props are real common on those, in fact I'd bet that's what's on there now. Because the 17s are so common, I'd assume you can borrow one (or pick up a good used one cheaply). Try it, read the rpms and go from there. <br /><br />Nearly all the props I've seen on those V4s are either OMC or Michigan. Michigan's have their model numbers on the face of the prop where the prop nut sits, & they often get crudded up with exhaust & corrosion. A little scuffing with some sandpaper & you may find the numbers right there. Post back if you get them.<br /><br />How hot are the cylinders? Those older V4s had the thermo/venostats start opening at somewhere between 105 and 130 degrees F. When she's fully warmed up, you should be able to rest your fingers on the sides of the cylinders for 3 seconds or so, without getting burned, before you have to pull them off from the heat. They'll be fairly hot, not just warm, but you shouldn't be anywhere near getting burned. If they're hotter than that, you've got problems and you shouldn't run the motor until you get it squared away - you may damage it (or are damaging it). Those didn't come with a telltale - did someone plug one in? If it's too hot, probable culprits are 1) impeller, 2) clogged water passages, 3) sticking/clogged thermostat or venostat.