Page 1 of 1

Yamaha F250 or F300 for a 23 Conquest

Posted: Thu Jul 05, 2018 9:59 am
by Ryansim12
Happy Fourth Everyone. I have an 2001 23 Conquest with original twin Mercury 135-HP engines. I may move to a single Yamaha and am debating between the F250 or the F300. My biggest concern is the weight difference. Any thoughts or experiences to help me with my decision?


Re: Yamaha 250 or 300 for a 23 Conquest

Posted: Thu Jul 05, 2018 10:59 am
by msirof2001
The new Yamaha F250 and F300 weigh the same, between 560 to 570-lbs. Probably the same or less than the twin Mercury engines. My 1995 21 OUTRAGE it was rated 150 to 300-HP. Given the larger size, if it were my decision, I would lean towards the F300. I have twin 300-HP engines on my Everglades and love them.

Re: Yamaha 250 or 300 for a 23 Conquest

Posted: Thu Jul 05, 2018 11:47 am
by Ryansim12
msirof2001 wrote:...if it were my decision, I would lean towards the 300...

Thanks. I am leaning toward that, too. I just want to make sure Im not missing something. Good to know about the weights. Thanks.

Re: Back in the club

Posted: Sat Jul 07, 2018 12:36 pm
by Mambo Minnow
That boat was USCG rated at max 250 HP. If you power with 300 you may have trouble getting insured with your carrier.

{This comment was originally posted to another thread, where is made no sense. I believe the comment was intended for this thread and I have moved it here.--jimh]

Re: Yamaha F250 or F300 for a 23 Conquest

Posted: Sun Jul 08, 2018 2:54 am
by msirof2001
[Isn't the boat under discussion in this thread the same boat as discussed] in the second post of another thread [discussing a different boat, the 235 CONQUEST and the same boat as discussed in this thread, a 23 CONQUEST] at

[In the other thread linked above the first comments refer to] a 235 Conquest with a weight without engines of 3,730-lbs and a 300-HP rating. The second post [in the other thread refers to] a Conquest 23 with a dry weight, without engines of 3,650-lbs. I believe the second post was [in reference to the 23 CONQUEST which is] the earlier model and more like [the boat under discussion in this thread].

I didn't see a maximum horsepower rating in this thread, and mambo minnow's 250-HP may have indeed been the maximum rating. (No--see below for the actual rating of a c.2001 23 CONQUEST boat being 300-HP maximium--jimh]

My [eight] thoughts:

--My 1995 OUTRAGE 21 was rated for a maximum 300-HP and the weight without engines was 2,500-lbs. The 1993 to 1997 OUTRAGE 24 weight without engines was 3,300-lbs and had a max HP rating of 400. There is an 80-lbs difference between the older Conquest 23 and the newer Conquest 235. I feel this is immaterial.

--The weight of both Conquest boats exceed the two aforementioned OUTRAGE models. I have a friend with a like-sized Robalo with a Yamaha 225, I have been out to sea many times with him, and I found the boat to be grossly underpowered.

--I have [read] many debates here at continuousWave (and elsewhere) whether insurance companies say you can or cannot re-power above the rated horsepower. People have asserted that you can, but I would recommend checking with the insurance companies beforehand.

--If there are headwinds, I would argue highlighting the similarities between the earlier Conquest 23 and the later Conquest 235 and that the latter was rated to 300-HP (insinuating that maybe the earlier Conquest 23 may have been under-rated with respect to max power).

--For people who have re-powered above the max power rating to chime in in this thread will be great.

--[The proposal engines are] not comparable to sticking a 7-Marine 625-HP on the stern.

--If this were my decision, and given the thousands of hours I put on my OUTRAGE 21 in the ocean, I wouldn't think twice about adding the Yamaha 300. In fact, I would even consider a pair of Yamaha F200XB's.

--Definitely do the research with the insurance companies.

Re: Yamaha F250 or F300 for a 23 Conquest

Posted: Sun Jul 08, 2018 9:05 am
by jimh
Rather than rely on anecdotal comments or inferences, the maximum horsepower rating of a 2001 23 CONQUEST as listed in the Boston Whaler catalogue was 300-HP. Re-powering a c.2001 23 CONQUEST with a 300-HP engine is entirely within the original ratings from the manufacturer, and there should not be an dispute about this, again, based on the catalogue listing.

Re: Yamaha F250 or F300 for a 23 Conquest

Posted: Mon Jul 09, 2018 8:45 am
by Ryansim12
Thanks everyone-- this will be my first re-power and I just want to make sure I was not missing something. I am thankful for the ability to tap into the knowledge here. I look forward to contributing to this great group

Re: Yamaha F250 or F300 for a 23 Conquest

Posted: Sat Jul 14, 2018 4:59 pm
by Mambo Minnow
A clarification. The original power for 1997-2001 Conquest 23 was for a single 250HP or twin 150HP, so in that aspect it could be powered for 300HP.
There simply did not exist 300HP motors, back then as a single with perhaps the notable exception of the Yamaha HPDI but that motor had a terrible reputation.

In fact, if you had a single 250HP motor, BW put lead in the keel to compensate so by today's 4 stroke standards, you would likely be safe repowering with a single 300HP four stroke engine.