TOPIC: Getting spay/splash with new prop - 73 Evinrude 65

Hi All:

Hoping someone can help me diagnose a problem that started when I changed to new prop.

Boat is 73 Crestliner Muskie 15 tri-haul open-bow.

Motor is 1973 Evinrude Triumph 65 HP 3 cylinder, long shaft. This is the motor that originally came with the boat in 1973.

Old prop was the factory original 13.25" x 17P aluminum Evinrude prop.

New prop is brand-new OMC Viper stainless steel 13.85" x 17P (same pitch with cupping).

Note: I have a hydrofoil on motor (was there with the old prop, too).

Boat ran out with no prop-spray with original prop. Max RPM was 5400 RPM. New prop RPM maxes at about same. Boat is 5 MPH faster (now 34=35 MPH (was 28 max on old prop).

As all else is same, why am I getting tons of spray around the motor (some is splashing over transom, but not too much).

Should prop dictate mounting height? I did not take pictures or video yet, maybe next weekend.

The speed increase is great.

Goes on plane quicker, with a small lag off of idle (prob due to the grab of the cupping on the prop. Boat planes flatter and steers easier, too.

Not being able to see the relationship of the underside of the outboard's anti-ventilation plate to the hull bottom, this might be weak advice, but it sounds like the outboard could benefit from being elevated a little. I think that the standard upper mounting holes allow for 3/4 inch changes. If so, I would guess that raising the outboard 3/4 inch (one hole) might well be the solution. Also, if the original sealant used on the four outboard mounting bolts is 42 years old, it would be extremely wise to renew this anyhow.

Regards,
Joe
www.fergusonpoolemarine.com
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Thanks - from what I have been able to read you are probably correct. Is there a way to do this at my home, or do I need to take to an Evinrude service person? As I am new to boating, any input is appreciated.

Couple of questions:

1. Does it matter if the motor bracket is no-longer sitting on the top of the transom (will be a space equal to the amount the engine bracker is moved up)?

2. Why does this prop require me moving the motor higher?

Thanks to all for the help!

With common sense and planning ahead (locate wrenches and/or ratchet and socket, sealant, paper towels or rags, something to remove the old sealant from the bolts once removed, etc.), many can do such a repair at home. Sure, an assistant or two would be preferable to have also. Depending on the distance between the outboard's lower unit skeg and preferably a concrete or asphalt surface, place a wooden block (2X4 or larger) between the ground and the skeg to allow the skeg to rest on. If you boat trailer has a tongue mounted jack, this can be employed to lower the boat transom in relationship to the outboard (now sitting on it's skeg) once the two upper bolts have been removed (an assistant to steady the outboard, and a second to turn the trailer jack handle might be nice to have available), and the two lower bolts are loosened some (there should be slots for the lower holes). Note that leaving the two lower bolts in place should add some safety until both top two bolts can be reinstalled (once old sealant is removed and new sealant has been applied to their shanks) and they then have been at least snugged-up. Then the lower bolts can have their turn at being removed, cleaned, and new sealant applied. Although there are others to choose from, I like LifeCalk by BoatLife, as moisture helps cure this sealant, rather than slow or stop the cure.
1. No, it does not usually hurt anything for the outboard to not sit on top of the transom. Note that on some outboard transom clamps, a plate (aluminum is often best) may be wise between the outside of the transom and the outboard, because as it is "raised" the outboard clamps will now rest on the aluminum extrusion covering the top rear edge of the transom, instead of totally against the fiberglass (in this case). Many outboards were mounted even when new this way though.
2. My guess is it is due to the speed increase, and that the outboard may have been mounted too low all along. We have seen a very great many number of boats through the years where the outboard is not at it's best mounting height. Sometimes this is because of what propeller was chosen, or with a vintage boat, what propellers were available at the time.

Regards,
Joe
www.fergusonpoolemarine.com
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Joe,

I really appreciate your taking the time to explain so well. I do think I can do this, as my boat is in my garage on smooth concrete. I will get the sealant and make plans to get to it. I especially like how you explained the safe way to do it.

I am glad to have found this forum!

Another possibility is that the faster speed is affecting the hydrofoil. Removing it will likely add a few mph due to less drag.

Joe:

I raised it up 2 holes - puts the plate even with bottom of keel - it's funny that this boat lived its entire life with the motor mounted too low (the crappy aluminum prop just did not show the symptoms that quickly became apparent with the new prop). The method you suggested worked perfectly (and I did it by myself with no issues).

I think that this will add a couple of MPH just by reducing the drag and lessening ventilation. I can't wait for the weekend to take her out for a trial run (hopefully I won't have to drop back 1 hole..... cause I really sealed up those bolt holes.

I will take pics tomorrow and post.

If it still has issues I will try with the hydrofoil removed (it just makes it ride so much smoother in chop.

I will be interested in hearing about how fast you can get it going.

Glad to hear that all went well. It may be that still one more additional hole "up" could be helpful, but I would now recommend that you test what you have now, including the good advice of trying without the hydrofoil. The apparently "too low" mounting might be all the "cause" the hydrofoil was improving. Have fun and let us know how things turn-out.

Regards,
Joe
www.fergusonpoolemarine.com
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Well, I had the time to take the boat out for an evening trial run (got to the dock at 6:15 and the lake was smooth and empty - just a dozen or so boats on a 10 mile lake).

Boat definitely planed sooner, splash at motor mostly gone, but top speed was not much better. I stopped and moved the tilt pin out 2 holes, and not the boat is running 37 MPH on the speedo (I will check with GPS tomorrow). Totally different boat. I will move out 1 more pin tomorrow to see if still more to gain (prob could go up one more bolt hole, but I will wait for that after more testing. Once I have it tweaked I will try a run without the hydrofoil to see if I can get her over 40. Not bad for a 1973 65 HP Evinrude.

Thanks all for the help - will update after tomorrows play time.

Finally success. Must say I recommend the OMC Viper Prop.

I realize that I never re-timed the motor with timing light after replacing power pack. Manual says that timing should be reset if power-pack module is replaced. No other mechanicals were touched - could this be why my low speed idle is rough? Top end is very smooth. Engine does idle, but a bit jerky. No leakage from coils or wires.

Do you have a factory manual? Timing is set at the factory and rarely needs adjusting, if ever.

Yes - I have the Evinrude service tech manual used by dealerships.

Manual says to reset timing any time that power pack is replaced, when timing pointer is disturbed, whenever any parts affecting stator, or linkages are messed with.

i have the same problem for 10 yrs. the mantaray is a tunnel hull cat and the cav/vent plate is well below the tunnel..hence the problem. i could fix the problem by building up the transom.NOT tried a fin at the bottom of the tunnel i got from joe poole...made no difference, so i just live with the water coming over the transom. ron

If it were me I would definitely follow the manual and re-check your timing sir. Slight variances in parts manufacturing could throw things of just a tad.

A very wise friend once told me that nobody does more testing and research on propellers for their brand than the manufacturer of the motor! While there are a couple aftermarket companies that come close, it's turned out to be a very true statement in my findings.

Glad to hear you're getting her sorted out, tweaking for performance (best all around not just top speed) is a blast IMHO.

Took my son out with me Saturday. Did 35 MPH with the 2 of us and a third 6 gallon tank of fuel. Lake Tillery was very choppy, so we had to slow down. At 25 to 30 MPH was very smooth. Above that we smacked hard a few times.

Tried tilting out 1 more hole, but raised the bow excessively, so took it back again. Still have not checked the timing, but will soon.

Tried fishing, but caught nothing (only one good bite in a few hours). Will try earlier next time....