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Author Topic:   Doel Fin
Ben posted 04-24-2002 08:23 AM ET (US)   Profile for Ben   Send Email to Ben  
I just had my water pump rebuilt and the mechanic indicated the engine was running hot. He said that the doel fins were pushing the water away from the intake. I have a 200 HP 1977 Johnson. The 2 part molded plastic parts do appear that they could push the water way from the upper intake on the lower unit - anyone esle experiance this? Is there another model of doel fin to use?

Also - Were can I purchase the B12 carb cleaner in Michigam. Meiers and the local autoparts store did not have it.


kingfish posted 04-24-2002 08:45 AM ET (US)     Profile for kingfish  Send Email to kingfish     
I've used Doel fins successfully on a number of motors and never had any trouble such as your mechanic suggests; in fact I'm not even able to visualize how they could push water away from the intakes. Could you explain in more detail how he describes the event occurring?


acseatsri posted 04-24-2002 03:59 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
I just installed a Stingray on my 18OR along with transom wedges (older OMC's are known for not having enough negative trim adjustment). Let you know how it works in a week or two. In the meantime, the fin is WAY behind and above the water intakes. Really don't see any possible way that it could affect water intake.

PS- exactly where is there an "upper" water intake? The only intakes I see are the ones the muffs slip over for running on a hose.

Dick posted 04-24-2002 10:24 PM ET (US)     Profile for Dick  Send Email to Dick     
I have been selling Doel Fins, and other styles, for more years than I want to admit.
I have never heard of any kind of a problem caused by any of them.
larlander posted 06-29-2005 01:29 PM ET (US)     Profile for larlander  Send Email to larlander     
I have a question for you since you appear to be experienced in the perfromance of the Doel Fin.
I recently mounted them on my Honda 90/17' Montauk combo.
They work fine until I reach speeds of mid-30MPH and the boat starts to list dramatically to the port side.
This is with the Honda trimed in all the way.
When I let out the trim slightly it reduces and eventually as I continue to trim out, it goes away altogether.
Is this normal and to be expected?
bsmotril posted 06-30-2005 08:51 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Those upper holes are drains for the exhuast leg, and not intakes. Your mechanic is full of it. I've had doelfins and stingrays on several boats, never a problem like this. Never heard of any others either. Because of the location of the actual intakes just above the bulge from the prop hub, there is no way a doel fin could force water away. If anything, they'll help keep water over the intakes with a high mounted motor. BillS
bsmotril posted 06-30-2005 08:53 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
What you see is normal, and is caused by the torque of the prop. Almost every single engine outboard will list to port when trimmed in all the way. The fin may amplify this effect a bit. If you adjust the trim tab on the motor for neutral steering feel at your optimum trim angle at your most used cruise speed, you can tune out the effect at the speeds you run most. But, you'll never eliminate it with the motors trimmed in unless you go with contra rotating twin motors. BillS
kingfish posted 06-30-2005 09:16 AM ET (US)     Profile for kingfish  Send Email to kingfish     

Additional to BillS, if your DoelFin is having *any* effect on the trim or performance of your boat at mid-30 MPH, you should probably move your motor up a notch or two. The idea and effectiveness of the DoelFin is to help get on plane at lower speeds, and to hold plane at lower speeds. Typically when your motor is set at the height for optimum performance, the Anti-Ventilation plate (and consequentlly the DoelFin) is above the flow of the water at high planing speeds.


bigjohn1 posted 06-30-2005 10:14 PM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Just one more reason I personally ask, look up, study, and try to independently verify just about anything a mechanic tells me these days. This thread, and the responses thusfar, should demonstrate that point to you....good luck!!
pwitort posted 07-10-2005 03:42 PM ET (US)     Profile for pwitort  Send Email to pwitort     
any suggestion on a process to adjust the trim tabs to get to the desired position most quickly?
jimh posted 07-10-2005 04:48 PM ET (US)     Profile for jimh  Send Email to jimh     
The Boston Whaler Owner's Manual has a procedure for adjusting the trim tab on the outboard motor:

Is this what you are asking about? You mention "trim tabs", and there usually is only a single trim tab to adjust on a motor.

pwitort posted 07-12-2005 02:56 PM ET (US)     Profile for pwitort  Send Email to pwitort     
Hi Jim,

just noticed that was you! thanks for the response. Yes, there is only one trim tab.

Im just about to repower and could use company breaking the motor in... tuna are here 30 miles out, crabbing is ok; AlaskaAir probably has a deal... come on down and thaw out :)


Royboy posted 07-14-2005 10:56 PM ET (US)     Profile for Royboy  Send Email to Royboy     
I recently installed a Stingray on my engine and as I understand it, the thing is barely in the water when on plane, just as the anti-cavitaion plate it's mounted to would be. I let anyone lese drive yet so I can go back and take a look, but I can hear air sucking through the small gap between my fin and the anti-cav plate. Check to see that the anti-cav plate is within an inch of the bottom of your boat. That is to say, it should be even with the lowest point of the bottom of the boat plus or minus an inch. Apparently, when on plane, there ain't much boat actually in the water.

Needless to say, ALL of the water intakes are below your anti-cav plate, (or they wouldn't be in the water when on plane)so your mechanic is blowing smoke.


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