Re: [omc-boats] Tach's Speedo's & Redlines - Long Post

Lee,

Seems like awfully good performance at that altitude. Congratulations on your successful engine swap. I've been thinking of changing out the relays on my power tilt. I do have the hand-wheel so I could survive a failure. I did installed a new starter and change out the starter relay. Last thing I want is to get stuck out on Lake Michigan with a failed starter. I look at it as cheap insurance.

I actually had my last Rogue pitched down, quicker hole shoots for multiple skier's. Losing a few MPH didn't really make much difference, after all it's not a Cigarette boat.

Glenn
 
  ----- Original Message -----
  From: lib1@...
  To: omc-boats@...
  Cc: Shuster (leeks) Lee
  Sent: Thursday, September 01, 2005 9:08 AM
  Subject: [omc-boats] Tach's Speedo's & Redlines - Long Post

  Hi,

  I got home last night from spending the "perfect" day on the lake and got to read the interesting thread about engine RPM's, max redlines, etc.

    First of all the day didn't start out too well. When I got the boat on the ramp at 10:00 am (an hour from home) and it dawned on me that I left the boat keys at home. (and during the engine conversion, the spare key that used to be kept in the engine bay, didn't get moved.)

    Fortunately, I yanked out a couple of test leads from my toolbox and quickly jumpered the ignition switch. Only to discover I could not lower the sterndrive. The (tilt) DOWN Relay was clicking but no tilt motor action (and this was the first sign of failure, as it was working fine three days earlier). Some quick troubleshooting proved the fuse was OK because the UP Relay would activate the tilt motor (also no manual hand-wheel on this newer tilt motor). A voltmeter quickly revealed the DOWN relay had no output. Even banging on it with a hammer while someone else toggled the switch didn't wake it up. I thought about removing the quadrant gear (three easy bolts) but I don't have enough (only about a 1/4-inch) road clearance to launch her in the full down position. Looked like a long drive home.

    But wait. One could physically swap UP/DOWN relays? Or easier yet -- make a quick jumper wire that allows the UP Switch/Relay to first LOWER the motor, then remove the jumper and re-install the UP motor wire on the UP Relay when it's time to get back on the trailer at day's end. So that's just what I did. (Just remember to only hook up one motor wire at a time.) Worked great. Now if I can only find that brand new relay out in the garage! Anyone know a NAPA equavalent p/n for our tilt relays ?

  I mentioned the day was boat-perfect, because it was cool, dry, cloudless and almost no wind. We had very smooth, glass-like, water and had the 10 miles of open lake practically to ourselves. It was a great day to take a borrowed GPS along and verify some speeds:

    To my utter amazement, the boat's original (1966) speedometer was spot on with the GPS! I posted the results on my website at: http://hhscott.com/evinrude/GPS_Speed.htm
    I also took along a second, newer pitot-tube speedometer and it also tracked very closey with GPS. My tach has been replaced and it has been cross-checked against another Sun shop tach. Frankly, I was surprised to see both pitot-tube speedo very close to the GPS, once they get over 10 mph.

    With the V8, I seldom have a need to push it much past 3500 RPM. At that speed, (except for holeshots) it runs very economically on the smaller primary (front) barrels of the QuadraJet. It was fun to "firewall" the throttle and let her climb up to a maximum observed RPM of 4400, where we observed a top speed of 37 mph. If I lightened up the gear that seems to find it's way into the boat, the second crew member and the full tank of gas, and went up a notch in pitch, re-waxed the hull, I might see 39 mph. You have to remember this is at 6100 ft, where effective horsepower is down about 25%, even when jetted perfectly. The neat thing with the torque of the V8, coupled with it's gearing, combined with the prop, is it gains RPM fairly rapidly, even when going from 3500 RPM to WOT. The last 200 RPM take a little longer, but man does it sound cool. At all other times it's a quiet as a mouse (bad pun for you SBC lovers). It's fun to "wring her out," but unless the water's glass smooth (like today) and there's little or no other boat traffic, it's not very practical to grab that last 5 to 8 mph.

  I'd have to agree with the previous posts in this thread. 1) Verify or calibrate your tach. 2) Shoot for no more than 4200 - 4400 (actual) RPM. Maximum redline.. You gain very little, if anything except excess wear & tear, excess fuel consumption, by over-speeding the engine and sterndrive nuch beyond 4000. 3) Tailor your prop to your needs. As boats age age, hulls hook or get dirty or gain water weight, motors lose some of their original snap, and we all are guilty of inviting one too many friends onboard. I'd consider downsizing the pitch of your prop or trying an SST (Stainless Steel Teflon-coated). See my write-up on choosing OMC props: at http://www.hhscott.com/evinrude/choosing_a_prop.htm Also, I couldn't agree more with the list member who suggested giving these engines be given a bit of a break, (my self-imposed, safe, practical, more economical, (meaning run it all day) redline is 3500 - 3750.

  Speaking of water-skiing -- I almost forgot to mentioned. I posted some great deep-water-start slalom pics on my website at: http://hhscott.com/evinrude/gallery_3.htm taken last weekend.

  The holiday weekend's nearly here and it will probably be our last weekend on the water, too.

  Lee Shuster
  Salt Lake City

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Received on Thursday, 1 September 2005