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question about propeller racing in foul seas

Posted: Sat Aug 19, 2017 8:11 pm
by Maestro
We trailered our 28 to Green Bay (the body of water, not the city!) for a trip last week and had great weather most of the time.

One of the days, we smashed our way through 24 miles of stiff 3-4 ft waves. Throttled to 2,000 rpm which equated to about 8-9 mph in those seas. In normal conditions that rpm would give me about 14 mph.

The boat did very well, but on several occasions, the propeller rose briefly out of the water and you could hear it race. Makes angry groaning/roaring sounds. Engine rpm seemed relatively unaffected. A little tremble on the tach.

Should I find myself in this position again - is the prop racing going to destroy anything ? I certainly can't imagine its good for any part of the drivetrain but I don't see any way to avoid this when caught in a stiff chop. Reducing speed further would result in very poor steering...

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 5:43 am
by Fastjeff
..."We trailered our 28 to Green Bay (the body of water, not the city!) "

Had to laugh at that since my GPS has me running up the local river on dry land! (The pointer is off about 3/4 of an inch.) Weird to see buoys located on dry land!

If the props were breaking free, either those was some really nasty waves you were running in, or the boat was trimmed (weighted) too heavy forward. I've banged through a few nasty conditions with my old 32 footer and never experienced that. Do you have trim tabs, and were they down at all?

I doubt if any permanent damage was done to the engines (assuming they didn't over speed) or the trans. The shafts didn't break (obviously) so they're probably okay as well.

Jeff

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 8:30 am
by Maestro
I have tabs but they are not working at the moment so they are set fully retracted.

Waves were very steep, period very close together. I think that was part of it.

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 11:45 am
by TinLizzy
I have had my twin engine 28 do this many times on Lake Superior. In my mind, it is just the nature of the beast. Having a very shallow draft, makes it easier for the props to break free in the rough stuff. Tabs are a must, but they only help so much. Just keep doing the balancing act between pounding and being able to steer effectively/make head way.

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 12:51 pm
by Maestro
does running the tabs all the way down help keep the prop under?

My tabs have never worked but I've been tinkering with them this summer. It's been a slow process but I hope to have them running soon.

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 8:49 pm
by martindesign
Cavitation, it happens. Not ideal but at that speed and rpm won't hurt anything.

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 9:19 pm
by TinLizzy
Depending on sea conditions, the tabs could help out with the prop free wheeling. But the trim tabs are so much more. I would say on a typical cruise, at 25- 30 mph, I use my tabs a couple of times every few minutes. I have 5 kids, and they are always walking back and forth, and side to side, while we are under way. I use the tabs to keep the boat as level as possible side to side, and also adjust fore and aft to account for sea conditions and to fine tune for max mph while cruising.

Re: question about propeller racing in foul seas

Posted: Sun Aug 20, 2017 10:48 pm
by jralbert
In bad weather, passengers should be told to stay put, roaming not very safe. If you have strong/heavy/big following seas (not good), tabs should be off/retracted/up. Or at least in a neutral positon. If they are down, they will keep the nose down and when you ski down a fast moving roller, the bow is likely to dig in and you could flip end over end (also not good).

If you can manage to head into waves, a small amount of tab down can steady things. You'll be taking it slow and steady and you'll get home safely.

Re: question about propeller racing in foul seas

Posted: Tue Aug 22, 2017 6:58 am
by Fastjeff
Perfect answer, Joel!

Jeff

Re: question about propeller racing in foul seas

Posted: Tue Aug 22, 2017 6:50 pm
by TinLizzy
I was referring to people moving about the boat while cruising, not when it is rough. I should have clarified. I don't go out with my kids if it is rough. My main point was that I use my tabs all the time.