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2000 Dauntless 22' Cavitation in turns
Sassa Whaler	#1  Posted on 06/05/16 - 5:30 AM
Member Posts: 14 Comments: 0 Joined: 04/25/16	My Dauntless 22' with a Mercury 200 is giving me some fits with cavitating in sharper turns. I usually cruise around 3800 RPm's at about 26 Knts. I have a Merc High Five 21P prop that came with the boat. All indications are that the boat is propped correctly, netting about 5,500 rpm at WOT loaded. I have no jack plate or anything and the motor is mounted at the factory recommended mounting holes. The river here has quite a few sharpish turns and it breaks loose and cavitates all the time. It is really bad if I try to do a quick 180 even at slow speeds. Trimming down before the turns does not seem to help much. I have had good luck on previous boats with cavitation/ stabilizer plates. Anyone using these with any success? Any other suggestions? I am finding not to be a big fan of the Merc High 5 prop and may change that. Great hole shot, but horrible in reverse in this boat. Any suggestions much appreciated. Edited by Joe Kriz on 06/05/16 - 11:04 AM
butchdavis	#2  Posted on 06/05/16 - 7:13 AM
Member Posts: 826 Comments: 0 Joined: 11/22/11	There seems to be no perfect prop for any boat. If you want hole shot you sacrifice speed, etc, etc. Generally, most Boston Whaler owners find the factory engine mounting position is not high enough for optimum performance. Some experimentation may be required to find the "just right" mounting height. Another critically important factor is engine trim. With a high five prop you can probably leap on plane regardless of trim setting, but most of us have to trim the engine fully down to achieve "best" hole shot. For best top speed and/or maximum fuel economy I must trim the engine up until the boat just begins to porpoise then trim down very gradually until porpoising stops. The problem is that when running along at speed and attempting very sharp turns with the engine trimmed for optimum cruising operation a sharp turn can cause "blow out". The easy solution is to trim the engine down a bit before making a very sharp turn. When towing toys or skiers this can be very annoying, so when engaged in towing just trim down enough to make your turns and leave the engine there. Butch
Joe Kriz	#3  Posted on 06/05/16 - 12:00 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11430 Comments: 452 Joined: 03/18/05	Sassa Whaler wrote: I have no jack plate or anything and the motor is mounted at the factory recommended mounting holes. What is the factory mounting hole position for your boat/motor? http://www.whalercentral.com/articles...cle_id=106 Did you purchase this boat new? Is this the original motor or is this a replacement?
Sassa Whaler	#4  Posted on 06/06/16 - 5:53 AM
Member Posts: 14 Comments: 0 Joined: 04/25/16	I am the third owner. The motor is original that came with boat in 2000. Boat was set up and purchased at Marine Max in South Florida. The motor has not been moved to my knowledge. Yes I have plenty of hole shot regardless my trim. The issue is that even if I trim way down prior to the sharp turns I still get blowout. At one point last weekend I had the motor trimmed fully down and was still getting blowout in sharp turns even at non-planing speeds. I will check out the link provided (thanks) to ensure the motor has not been adjusted. Just was not sure if folks were having luck with these optional items that may help this. I am not a speed burner. Normally cruise at 3800 rpm at about 26 knots. Just having the blowout running the river is a big pain. Thanks for all the help! James
Sassa Whaler	#5  Posted on 06/06/16 - 6:03 AM
Member Posts: 14 Comments: 0 Joined: 04/25/16	Just looked. It is a Mercury 5 hole mount. The motor is mounted in the middle hole or Two Holes Up per the link provided.
Phil T	#6  Posted on 06/06/16 - 8:49 AM
Administrator Personal Page Personal Album Project Albums Posts: 6985 Comments: 6 Joined: 03/26/05	Lower the engine 1 hole and re-test. FWIW, the Hi-Five (5 blade prop) is not a typical prop for a Boston Whaler and was a replacement prop. Are the PVS plugs in or filled? In 2000, the selling dealer would supply the prop, most often an economy aluminum prop. Boston Whaler now includes a Mercury Enertia prop with the motor.
Sassa Whaler	#7  Posted on 06/06/16 - 11:58 AM
Member Posts: 14 Comments: 0 Joined: 04/25/16	Phil T, thanks for the reply. Yes, the high five was put on by the previous owner. I am considering going to a 3 or 4 blade prop. My concern with dropping the motor down to hole #1 is that the Merc lower unit has that double cavitation plate/ splash plate. As it stands now, if I do not trim the motor properly, the cav plate "digs in" causing spray at the stern and very tuff steering. However I may try that and just trim up even further. I fear this the higher trim level to prevent the "dig in" with result in the same cavitation problem. No hurt in trying tho. Guess that is why I was asking about the use of hyrofoils to obtain the stern lift, stability in turns and anti-cav properties.
Phil T	#8  Posted on 06/06/16 - 2:40 PM
Administrator Personal Page Personal Album Project Albums Posts: 6985 Comments: 6 Joined: 03/26/05	I would guess the previous owner changed props to improve acceleration and/or increase minimum planing speed and/or to pull skiers or a tube. All outboard motors need to be trimmed. At speed a motor that is not trimmed out enough will lead to increased effort to steer. At mid range speed the anti-cavitation plate should be at the surface of the running water and throw any prop spray flat. Almost all motors are mounted too low. Any boat running at 25 mph with a correctly propped and rigged engine will ventilate when doing a sharp turn. I would guess a 4 or 5 blade will ventilate more than a 3 blade prop. My Outrage 17 and Montauk 17 ventilated when doing high speed hairpin turns. A hydrofoil or tabs or dole fins are might "help" but they are compensating for a problem in the rigging or prop. Keep in mind the Dauntless is a very beamy, shallow deadrise and heavy for it's LOA. I would not expect it to have the performance characteristics of an Outrage model. Personally, I would look at leaving the motor alone and changing the prop (stainless not aluminum). You will trade off lower planing speed, acceleration for turning ability. Verify in your manual that your engine WOT is 5500 and not 5750 like some Opti 200's. From a historical conversation I read the original performance report for your boat/motor from Boston Whaler reported 47 mph at 5750 running a 15 1/2 x 17P Mirage Plus propeller. This was with the boat practically empty.
Sassa Whaler	#9  Posted on 06/06/16 - 2:50 PM
Member Posts: 14 Comments: 0 Joined: 04/25/16	Great info Phil T. Next outing I will let the wife drive and check the cav plate in the water. I understand the Dauntless is not a turning machine, just making sure everything is correct. Will update and let you know. Thanks all for the advise.