Uneven Wake Pattern 50HP Outboard

Any ideas on why the wake pattern from my outboard would be uneven? There is a lot of extra spray coming up on the starboard side. This engine, a 1985 Force, had been sitting while I restored the boat (that took two summers and this forum!), but it worked great when I took it off. Also, when I turn to port, it feels and sounds just like a clutch slipping in a car. The photo was my first sea trial after the restoration. This forum has been great except you guys didn't tell me something really important when I started this whole thing...the #@$%! money! Thanks for any advice, once again. jt

 

i have no idea about outboards,,,,,but i bet once you get the answer,,,,,its gonna cost ya lots of money
hehe
sorry,,,,,this thread just SCREAMED for this post hehe

 

A few questions:
When at rest, is the hull on an even keel?
" " , does she sit to her waterline correctly?
Is there a speed or depth transducer on the starboard side?
Is the VERTICAL trim tab on the motor facing directly aft or is it skewed to starboard?

From the photos it seems obvious that something on the starboard side of the hull or motor is creating its own significant wake.

 

The boat, at rest, is on an even keel. It still tracked evenly, under power, while the uneven wake was produced. There are no through hull electronics installed (so nothing protruding on the hull). The doel-fin trim tabs are mounted straight. As far as her waterline, not sure what that means... I'm trying to understand why this would occur now, when it didn't occur before I took the motor off. Why would it slip (like a slipping clutch in a car) when turned to port? Hmmm....

 

From the looks of the 1st photo...

the boat was heading straight, you aligned the bottom of the picture frame with your transom. the land in the background is tilted. Boat looks like she's listing to port and the wake seems to be thrown up from the starboard chine creating lift.

just hazarding a guess here... how does the planing/lifting strakes looking?

 

Hi wheresbob,

Yours is a bit of an unusual situation here. The asymmetrical spray pattern is quite common; there are a few possible causes.

One of the more common causes of spray problems behind an outboard is that the engine is set too low; thus, a bit of the non-streamlined casing above the antiventilation plate (to which your whale tail is affixed) extends below the transom. This sends spray flying everywhere. But it also makes for slightly sluggish performance, and makes your second problem- the "clutch slipping" feel- pretty much impossible.

That feeling you describe as being similar to driving a car with a dead clutch, is often caused by propeller ventilation. What happens here is that when you turn, the steady flow of water to the prop is disrupted- and if the prop is too close to the surface at that time, it sucks in air. Mixing air with water cuts resistance, causing the prop to spin faster, but also cuts thrust. If this is the case, it implies your engine is set too high or trimmed out too far.

It's possible that your engine is set too high, and the trim tab (that spade-shaped thing hanging above and behind the prop) isn't set right. You'd feel a significant pull on the wheel ("torque steer", to car people) at some speeds if this is the case.

What would really help is a few more photos to tell exactly how your engine is rigged. A profile view of the hull underside and motor would be great. If you can have someone hold a broom handle against the keel, extending out past the engine, that would be very helpful as it would let us see exactly how your motor is positioned relative to the keel.

 

Thanks for your reply, Matt. You'll see this shaft is too long by about 6 inches (15cm)... I learned this from the forum! However, before I did the blister repair and painted the boat, I did not have the asymmetrical wake pattern. This has occurred since I remounted the motor after it sat for a year and a half. The boat used to kick up a nice even wake...

 

Your prop looks like it has been bent & hit and this could induce some cavitation at higher revs. But if the latest images are where the motor sits, may be too deep, but I am not an outboard or any-other expert, just a keen observer...

 

Yes, I agree masalai, the prop looks worn...but why would I get an uneven wake now when it didn't occur before? The prop has not recently been hit or bent - it was like that two summers ago and everything worked well. The strong running motor was one of the reasons I decided to "fix" the boat up.

 

Not only worn but bent and leading edge with a "ding" too does not take much to stuff up the works there....
? - Go for a run, have someone hold the steering on course and have a quick look over the back to see where the spray is coming from - even a quick pic or three.... and Does the boat really need that big batwing?

 

Ha ha... It wasn't broken when I took it off the boat, so I never considered if the 'batwings' were necessary...

 

Some observations:

She's torque steering a little and ventilating the starboard chine which is tossing off a fair amount of spray. If you're getting some helm pressure associated with this, then adjust your trim tab (just above and behind the prop).

An enlargement of your prop shows a pretty torn up leading edge, have it trued or replace it.

Consider moving the engine over an inch or two to starboard.

The motor is mounted too low.

Is there more twist on the starboard side of your cavitation plate addition?

 

Off by 5-6" suggests that a long shaft motor is on a transom meant for a short shaft. That works just fine, but you'll have extra drag (thus a loss in speed and acceleration) compared to having it at the ideal height.

You may not notice it, but are you having to steer slightly to one side to keep a straight course? Could be that you need to tweak that little trim tab so that the engine itself is actually pointed straight ahead. If it's cocked a bit to one side when cruising, the flared housing where the lower unit meets the shaft would be diverting a good stream of water up to one side.

The slipping problem is gonna need a bit mroe thought, I'm about to lose my connection due to this frigging massive thunderstorm.

 

Marshmat,
Take some pictures and post on "Random...." I have forgotten what a cloud looks like hehehe

Keep safe, and be careful....

 

The plates seem to be similar; starboard not twisted more. And at higher speeds, when the uneven wake kicked up, there was some steering resistance - it pulled to starboard. It's gotta be the prop, versus the hull...there's not much going on with the hull - it's fairly flat overall... Maybe the engine is cocked to one side although it looks square here in the driveway. Hmmm.