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Author Topic:   Boston Whaler Boats That Can Be Upengined
WisED posted 04-15-2010 06:50 PM ET (US)   Profile for WisED   Send Email to WisED  
My old Boston Whaler 235 CONQUEST is rated for up to 250-HP. The new 235 CONQUEST is rated for 300-HP. Can the original be upengined to the 300?
jimh posted 04-15-2010 11:37 PM ET (US)     Profile for jimh  Send Email to jimh     
What does "upengined" mean?
Dauntless 180 posted 04-16-2010 07:22 AM ET (US)     Profile for Dauntless 180  Send Email to Dauntless 180     
From what I understand BW will not change your current capacity plate
number9 posted 04-16-2010 08:26 AM ET (US)     Profile for number9  Send Email to number9     

Since your Conquest is 20' feet or more the regulations requiring BW to have maximum hp on the certification placard doesn't apply. BW and most other OB boat builders put their maximum recommended hp on the placard. There is no USCG regulations that would prevent re-powering with a 300 hp. Some state laws prohibit re-powering over the maximum for boats less than 20' but none I know of apply that on larger boats. Best to look at your state regulations to make sure.

BW might not cover a hull warranty issue if re-powered over their maximum recommend for your model year. It could be an issue with your insurance company. Since BW doesn't go back and amend the previous years recommendations you may want to contact BW and your insurance company to ask some questions.

Buckda posted 04-16-2010 09:07 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Also check local regulations where you live. I doubt you'd have a problem with local sherriff's on such a large vessel, but many communities have ordinances that specifically state to go by the HP on the placard, regardless of length.

(Note: none of this stopped me from "overpowering" my 150 HP rated 18 with 180 HP in twin engines)....

WisED posted 04-16-2010 09:43 AM ET (US)     Profile for WisED  Send Email to WisED     
Just a theoretical question. I believe that the original rating was due to the availability of the new verado. Maybe someone aound here knows... was the verado 300 available in 2005-2006? The hull is exactly the same.
WisED posted 04-16-2010 09:45 AM ET (US)     Profile for WisED  Send Email to WisED     
Jim "upengined" relates to a bigger egg beater on the transom ;)
WisED posted 04-16-2010 09:55 AM ET (US)     Profile for WisED  Send Email to WisED     
I just answered my own question! Yes it will fit just fine. The main reason engine size is limited by design is weight of the engine. The 235 is designed for 700lb max. The Verado 300 weighs exactly the same as the 225; 635 lbs. Thanks!
number9 posted 04-16-2010 10:46 AM ET (US)     Profile for number9  Send Email to number9     
The 300 wasn't but the 275 Verado was. Possible they rated in more conservatively since the boat was new to their line.

Something to keep in mind, though I did read on another site with twin 300's there was only a 1 mph drop. The current owners manual:
Mercury Marine engines will operate satisfactorily when using a major brand of unleaded gasoline meeting the following
USA and Canada - Model 275 and 300: Having a posted pump
Octane Rating of 92 (R+M)/2 Octane is required for best
performance. Having a posted pump Octane Rating of 87 (R+M)/
2 minimum is acceptable, however, performance losses may
occur. Do not use leaded gasoline.

WisED posted 04-16-2010 11:47 AM ET (US)     Profile for WisED  Send Email to WisED     
That also true for cars with high compression gas engines. Lower ocatne gas leads to automatic timing retardation to eliminate engine knock, thus a few less HP. What makes the 300 very interesting is that it offers significantly better performance but essentially the same efficiency. An upgrade to a 250 really makes no difference. According to whaler performance specs.

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