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Author Topic:   Dauntless 18, 135 OptiMax
doscaballo posted 03-28-2007 09:36 AM ET (US)   Profile for doscaballo   Send Email to doscaballo  
Hi. I just took out the 1998 Dauntless 18 this last weekend after getting it back from the shop. This was the first time I have had it out on the water since purchasing it.

One thing I noticed is that the engine speed seemed really high for the boat speed I was going. I thought the tachometer might be in need of calibration. It easily went over 6,000 if I gave it full throttle. I only kept it there for a second. [The propeller has] four blades, stainless steel, but I cannot see the manufacturer's name. I checked the prop that night and by measuring, it looks like it's 13-inch diameter. A fragment of the part number has "17p" in it, so I assume it's a 17-inch pitch. I looked at WHALER.COM performance data, and they use a 15.5-inch 17-inch pitch propeller. This is making me think I am way under-propped motor for this boat. Does my boat seem under propped? If you have a similar setup, tell me what propeller you are using. Thanks in advance,


nydealer posted 03-28-2007 01:06 PM ET (US)     Profile for nydealer  Send Email to nydealer     
I think Whaler may have shipped it out with a 17P but two of the 18 Dauntless I looked at from 1099 and 2001 had 15-1/4 x 19 P Mirage three-blade. Your RPM range is 5000-5500. You don't want to get above that.
Lars Simonsen posted 03-28-2007 08:36 PM ET (US)     Profile for Lars Simonsen  Send Email to Lars Simonsen     
I have a 1998 Dauntless 18 with a 135 Optimax as well. I had a stock 17-inch pitch aluminum propeller originally, and it was definitely under-propped. I now have a 19-inch-pitch 3-blade Stilleto stainless steel. I also raised the motor up to the middle hole. I'm very pleased with the set up.

Once I raised the motor, however, I found that I had to come off plane more slowly, as my stern would sink more, and if I came off plane quickly, I could get water into the motor well. Since then, I've also put trim tabs on. Now, when I'm coming off plane, I lower the tabs and trim the motor down. This keeps the stern up, and also puts you in the position to jump back onto plane when you take off again.

doscaballo posted 03-29-2007 02:49 PM ET (US)     Profile for doscaballo  Send Email to doscaballo     
Ny and Lars,

Thanks for the reply. I think I definitely need to investigate this more.

Lars, you said you currently have a 19 pitch prop. Do you happen to know the diameter of it?

Thanks again,


Lars Simonsen posted 03-29-2007 09:05 PM ET (US)     Profile for Lars Simonsen  Send Email to Lars Simonsen     
I don't but I'll see if I can find out.


Tom W Clark posted 03-30-2007 01:14 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
The three blade Stiletto to fit a 135 OptiMax is the Advantage II. The diameter of the Stiletto Advantage II is 14-1/4".
doscaballo posted 03-30-2007 08:21 AM ET (US)     Profile for doscaballo  Send Email to doscaballo     
Thanks everyone. I called the local Boston Whaler boat dealer and he claims that similar setups have always come in with a 15.5 x 17-inch- pitch Mirage. I ordered a Solas aluminum with the same specs last night. I will have to hold off on the stainless for a while. In the meantime I hope to get my WOT RPM into specification. I will try and post some results.

Thanks again for all the help,


jimh posted 03-31-2007 03:23 PM ET (US)     Profile for jimh  Send Email to jimh     
I think most of the time the "Mirage" propeller is mentioned here the actual,propeller being discussed is the Mercury MIRAGEplus three-blade propeller.

The marked pitch on a Mercury MIRAGEplus propeller is often somewhat understated, or, in other words, a MIRAGEplus marked with a 17-inch pitch often performs like other propellers marked with a higher pitch, say 19-inch.

I have tested a MIRAGEplus propeller in several pitches, and, when comparing them to other propellers, found that they consistently performed as though their pitch were about 2-inches greater than that marked on the propeller.

Lars Simonsen posted 03-31-2007 04:47 PM ET (US)     Profile for Lars Simonsen  Send Email to Lars Simonsen     
I looked today, and my propeller is a Stiletto Advantage II 14.25 x 19P, as Tom Clark said.
lakeman posted 04-01-2007 07:01 PM ET (US)     Profile for lakeman  Send Email to lakeman     
I'm running a Mirage Stainless steel 3 blade 17 inch and I get about 53-55K RPMs depending on trim water conditions and if the Bimmi Top is up. Just about perfect for the 135 opti on my 2000 18 Dauntless.
sosmerc posted 04-02-2007 12:51 AM ET (US)     Profile for sosmerc  Send Email to sosmerc     
The Optimax 135 should be sounding an alarm and going into "Guardian Mode" if you are really turning 6000 RPM. You should be up against the rev limiter. I think maybe your tach is incorrect...possibly due to the calibration dial being in the wrong setting. The calibration screw should be set for 2 stroke/6 pulse.
Lars Simonsen posted 04-02-2007 09:29 PM ET (US)     Profile for Lars Simonsen  Send Email to Lars Simonsen     
I had a 17" pitch aluminum prop on my 18' Dauntless with 135 hp optimax when I first got the boat. It would also easily rev to 6000 rpm, and it was clear that it would keep on revving if I had pushed it. So if the 1998 optimax has an alarm/rev limiter(which I assume it does), it didn't work on mine either (not at 6000 rpm, anyway). With my new 19p prop, I can reach 5500 rpm redline, but it takes full throttle, and the motor trimmed up as far as it can go without ventilating.
sosmerc posted 04-03-2007 10:13 PM ET (US)     Profile for sosmerc  Send Email to sosmerc     
Limiter on a 1998 135 Optimax is supposed to kick in at 5800 RPM. If you stay "on the limiter" long enough, you should get a steady, beeping horn.....and eventually rpm's will be reduced to 3000. At least this is what is supposed to happen.

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