We finally launched last week and traveled down the Chicago river to get to Lake Michigan. Great trip, nothing broke. I'll post pics of our trip in another thread. We previously had issues getting the outboard low enough in the water. Now I think it might be too low. I have a Evinrude Yachtwin 9.9 on the back of an O'Day 25. It has two cavitation plates. The higher one is a few inches below the waterline. The reason I think it might be too low is because under light conditions the bracket was skimming the water and the front of the motor would occasionally get splashed. Empty boat is spec'd to have a draft of 2.5' with c/b up. What's the general rule for outboard height?
How far down should she be dunked?
- Thread starter Project_Mayhem
- Start date
Cavitation plate below the waterline. You've two?
I guess you could incrementally raise it 'til it goes bonkers, then drop it back down.
It needs to be deep enough to get a good bite on the water. Water flowing past the keel and near the hull will be disturbed and will reduce the bite of the prop. Another factor is wave action, if the prop is too high it will come out of the water when the stern rises. Not good for the motor.
The Yachttwin is probably a long shaft motor. A long shaft motor is created by removing the lower unit and inserting a spacer and new drive shaft. The second higher cavitation plate is probably the joint between the lower unit and the spacer.
The Yachttwin is probably a long shaft motor. A long shaft motor is created by removing the lower unit and inserting a spacer and new drive shaft. The second higher cavitation plate is probably the joint between the lower unit and the spacer.
Dave is correct about the extension. I do have remote shift/throttle controls. At close to 100lbs this motor is too heavy to lift out of the water while sailing. The head also hits the transom when trying to tilt it. It is what it is for now. Last year the lower cavitation plate was just below the water line. The motor sounded very very angry in waves. Is there a range, say between X and Y inches below the waterline for the lower cavitation plate?
That issue is normally addressed in the manufacturer's or owner's manual. If the motor mounts directly to the transom, it'll be more difficult to adjust the height than if you have an adjustable spring loaded device that attaches to the stern. If you go with a bolted on adjustable mount you'll be able to kick the motor up when sailing or when you're not at the boat.
You can measure all you want but if you have sail up and get heeled over (depending upon which way) and need it, that outboard will do nothing but push air. I got hit with a surprise storm (they said afterwards winds were 74 mph!), tacking in a shallow bay many years ago and could not get a large genoa furled successfully. Wanted to get OB going but it was too far out of the water until I finally came about. Things finally worked out but I vowed no more OB's for me.
I have an OMC saildrive and it's awesome when it works but so far it has a pretty miserable track record. I totally get why I see so many boats with this engine and with an outboard
We had a fantastic official first sail today. 20+ knots of wind and 2-4ft waves spread pretty far apart. I made an adjustment to the bracket. It seems like its going to be a bit too high or a bit too low unless I modify the bracket. However, the motor would make an occasional gurgling sound (intake above water?) but the prop remained submerged. Most of the time the water line was somewhere between the two cavitation plates. Prop walk is also a non issue now that it isn't skimming the surface like it was last year
We had a fantastic official first sail today. 20+ knots of wind and 2-4ft waves spread pretty far apart. I made an adjustment to the bracket. It seems like its going to be a bit too high or a bit too low unless I modify the bracket. However, the motor would make an occasional gurgling sound (intake above water?) but the prop remained submerged. Most of the time the water line was somewhere between the two cavitation plates. Prop walk is also a non issue now that it isn't skimming the surface like it was last year
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Ok, I'll be the stickler here. That motor does not have anti cavitation plates. It has anti VENTILATION Plates. Prevents the prop from sucking air down along the leg. Two very different things.
That's actually a pretty interesting fact. I think the water intake is sucking in air now that it's raised up but its better than the motor going for a plunge. Prop stays in the water 99% of the time though
Take a good look at the cowling of the motor. The engineers designed them so that it would be very difficult for the engine to suck up water from an occasional wave. There are drain holes under the cowling and the carburetor intake is designed to keep water out. I would be more concerned about not getting enough cooling water and having the prop over rev when out of the water.
This is correct. Thank you for highlighting that paragraph. I was getting ready to break out a manual to snap a pic.
On my C25 with long shaft 8hp mariner, my prop is deep! I would say over a foot to the cavitation plate. The cavitation plate is actually at surface level with the mount up and tilt down. While inconvenient to throttle on the tiller, unless it's rough out (cruiser wakes for 40-50ft sea rays that are plowing) I rarely surface my prop.
A sailboat needs that prop deep. It's not a planing hull where there prop can be just below or at the surface level.
I was having issues controlling the boat in the harbor yesterday. The back end of the boat pulls hard to port when in reverse so I dropped it back down to the lowest bracket adjustment. Is there any way to reduce prop walk?
We had some good wind yesterday and looked back as we hit 30 degrees of heel. The cowling was almost halfway submerged! We rounded up and sure enough the motor fired right up!