170 DAUNTLESS Propeller

Optimizing the performance of Boston Whaler boats
waynec
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170 DAUNTLESS Propeller

Postby waynec » Thu Jun 01, 2017 7:23 am

I'm new to Boston Whalers so I'm looking for a little information. I recently purchased a used 2013 Dauntless 170 with a 90 HP Mercury with a four-blade propeller. Did the 2013 170 DAUNTLESS come from the factory with a four-blade propeller? Wide open [the engine can accelerate to] 5200 RPM with a [boat] speed in the low 30-MPH range. Does all this sound right? Or, should I think about a different propeller?. The boat gets on plane quickly without any effort.

Jefecinco
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Re: 3 blade or 4 blade prop

Postby Jefecinco » Thu Jun 01, 2017 10:21 am

Your Dauntless is powered very near the low end for decent performance. Based on that, the propeller installed is probably fairly close to optimum. However there are too many factors in play to provide a well considered response..

The propeller gurus will need a lot more information such as the exact propeller size and manufacturer, the rated maximum engine RPM operating range, the mounting height of the engine on the transom, the engine model, and how you use the boat.
Butch

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Phil T
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Re: 3 blade or 4 blade prop

Postby Phil T » Thu Jun 01, 2017 10:51 am

Boston Whaler does not supply 4 bladed props to any of its models.

The 2013 Dauntless 170 came from the factory with a 3 bladed Mercury Laser II 13 1/4 x 19. The performance report is attached.

I would guess the prior owner re-propped for tubing or carrying a full load.

2013Dauntless170perf2.jpg
2013Dauntless170perf2.jpg (54.77 KiB) Viewed 6033 times
1992 Outrage 17
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waynec
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Re: 3 blade or 4 blade prop

Postby waynec » Thu Jun 01, 2017 12:31 pm

Phil
Thank you for the information what you said makes a lot of sense. I may try to change the prop out to the 3 blade and see the difference. The only problem it's an expensive test. New SS prop is about $400

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Re: 3 blade or 4 blade prop

Postby jimh » Thu Jun 01, 2017 1:40 pm

It is hard to identify a Mercury 90-HP FOURSTROKE engine by name, because at least four substantially different engines have been identified by that same name.

Does the cowling on the engine have a domed top, having somewhat of a resemblance to a lady's professional hair salon drier from the 1960's?

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Phil T
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Re: 3 blade or 4 blade prop

Postby Phil T » Thu Jun 01, 2017 2:08 pm

Wayne -

Shop online for the best prices, they vary widely. Dealers have the highest markup.

Dan's has a good reputation, selection and price.
http://dansdiscountprops.com/index.cfm#boat-propellers
1992 Outrage 17
2019 E-TEC 90
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waynec
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Re: 3 blade or 4 blade prop

Postby waynec » Thu Jun 01, 2017 3:01 pm

jimh wrote:It is hard to identify a Mercury 90-HP FOURSTROKE engine by name, because at least four substantially different engines have been identified by that same name.

Does the cowling on the engine have a domed top, having somewhat of a resemblance to a lady's professional hair salon drier from the 1960's?

I would say it does. Slightly

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Re: 3 blade or 4 blade prop

Postby jimh » Thu Jun 01, 2017 4:22 pm

Here is some clarification on what an engine that is called a Mercury 90-HP FOURSTROKE could be:

--the 90-HP FOURSTROKE based on the 1.596-liter Yamaha-made block with carburetors and no SmartCraft with 2.33:1 ratio, sold until c.2005

--the 90-HP FOURSTROKE based on the 1.596-liter Yamaha-made engine with fuel injection but no SmartCraft with 2.33:1 ratio, sold only briefly in c.2005

--the 90-HP FOURSTROKE based on the 1.7-liter non-supercharged VERADO block without DTS, (AKA the VERADITO) with 2.33:1 ratio, appeared c.2006

--the 90-HP FOURSTROKE based on a 2.1-liter block with smaller gear case with 2.07:1 ratio, appeared c.2014

--the 90-HP FOURSTROKE COMMAND THRUST based on a 2.1-liter block with larger gear case with 2.38:1 ratio, appeared c.2014

You probably have the Mercury 90-HP FOURSTROKE also known as the Veradito, or little Verado, because it used the same displacement four-cylinder in-line engine block as the small VERADO engines, but no forced induction from a supercharger. Its cowling has a little dome on top.

A boat from 2013 is right on the dividing line. Mercury was using the VERADO block based engines to make a 90-HP model for about eight years, then they developed another line of no-forced-induction engines that used much greater displacement. These engine were revealed in June 2014. Since your boat is a model-year 2013, it was most likely built before those larger displacement engines came out. So you've probably got the Veradito engine.

You should have the owner's manual for the engine, and in that literature you should be able to find the specifications about engine displacement. That will confirm the particular variant of the 90 FOURSTROKE you have. You will also find the gear ratio and the recommended full-throttle engine speed range. Since that Veradito engine is no longer made, it is hard to find that data on-line, so if you have it, please contribute it to the discussion so we can better understand the performance you are getting now. Going by the Boston Whaler test data, you can assume the gear ratio is 2.33 and the maximum engine speed is 6,000-RPM. In the test data the engine is shown to be making 6,000-RPM at full throttle. But reading it in the manual for the engine on your boat would confirm those inferences.

If your boat only gets to 5,200-RPM, you may not be taking full advantage of the engine. Often on a high-RPM engine with four-stroke-power-cycle, the engine keeps making more horsepower as engine RPM increases. To get all the power you can, you often have to select the propeller to let the engine accelerate right to its RPM limit.