255 CONQUEST Re-power

Optimizing the performance of Boston Whaler boats
Ratking20
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255 CONQUEST Re-power

Postby Ratking20 » Sun Jul 28, 2019 9:43 pm

I plan to re-power my 255 CONQUEST. It presently has a Mercury OptiMax 225-HP. To be honest [the boat’s performance is] not bad when it finally gets on plane, but it struggles at times to do so.

I may buy a Yamaha F300 which has a greater displacement than the other 300-HP engines.

Will there be a significant difference [in performance with a Yamagata F300 on a 255 CONQUEST compared to a Mercury OptiMax 225]?

[The 255 CONQUEST with the 225-HP OptiMax accelerates to] about 31-MPH right now; engine speed is 4700 to 4900-RPM.

While I do want more speed. my main concern is better planing and mid-range.

Thanks

biggiefl
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Re: 255 conquest repower help?

Postby biggiefl » Mon Jul 29, 2019 11:00 am

What is max hp for that hull?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Ratking20
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Re: 255 conquest repower help?

Postby Ratking20 » Mon Jul 29, 2019 11:57 am

[The capacity plate on the 2002 255 CONQUEST states the maximum power as] 400-HP. And [I am] trying to stay with a single engine

biggiefl
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Re: 255 conquest repower help?

Postby biggiefl » Mon Jul 29, 2019 12:28 pm

Three-quarter of the rating up from roughly half the rating and the 255 CONQUEST should be quite faster than what you have now.

ASIDE: a friend has a 23 SeaCraft that is rated for 400-HP. The 23 SeaCraft Had twin Suzuki 115-HP engines and was re-powered with a single Suzuki DF300. Now the 23SeaCraft Top boat speed is almost 10-MPH faster and the fuel economy is much better.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

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Phil T
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Re: 255 conquest repower help?

Postby Phil T » Mon Jul 29, 2019 1:38 pm

R-

Have you already reviewed the engine mounting height, prop selection and trim tabs to refine what you have to as good as it gets? Some find their setup was garbage) and changing one or more of the three items mentioned resulted in a huge improvement.

If you already did the above.....nevermind.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

Ratking20
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Re: 255 conquest repower help?

Postby Ratking20 » Mon Jul 29, 2019 3:50 pm

I have not. We are going to repower regardless. But ive read all over that people say they are underpowered with 200 to even 300 hp on this hull.

biggiefl
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Re: 255 conquest repower help?

Postby biggiefl » Tue Jul 30, 2019 10:41 am

Before you spend $20,000, get some hard numbers from someone who has re-powered—if that is what you hear. I can't see how 300-HP would be lacking in power, but I would want to make sure.

I read here all the time where people think certain combos are underpowered, and I can vouch personally that they are not. Many will say a 115 on an Outrage 18 or Banana 19 hull is too weak—trust me it is not, unless you think more than 40-MPH boat speed is weak.

A 225-HP single engine is okay on a classic Outrage 25, but I know that boat is quite slimmer than your 255 CONQUEST hull.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

jimh
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Re: 255 CONQUEST Re-power

Postby jimh » Tue Jul 30, 2019 1:15 pm

A friend just bought a very nice gently-used 2005 255 CONQUEST with twin 225-HP Yamaha F225 engines painted black with Mercury cowlings. I am practically certain it was delivered that way. The 255 CONQUEST is a big boat—wider beam and very much higher freeboard than a classic OUTRAGE 25 hull. It also has a tall fixed hardtop.

That a 255 CONQUEST can reach plane with a single 225-HP engine is good news for my friend with twins; we were wondering if that hull would be able to plane on one engine.

Q1: What is the displacement of the Yamaha 300 engine?

Q2: Is that model the one with the flywheel that needs replacement every 100-hours or so?

Also, the 255 CONQUEST with twin F225 engines at static trim was still able to keep the splash well drains out of the water. By that metric the engine weight was no problem.

Q3: What does the capacity plate actually say on your 255 CONQUEST for maximum power?

Ratking20
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Re: 255 CONQUEST Re-power

Postby Ratking20 » Tue Jul 30, 2019 2:05 pm

A1: the Yamaha F300 is 4.2 liter and has a higher displacement than any engine of its size i think. Suzuki might be up there, too.

A2: the Yamaha F350 is the engine with the flywheel problems. I know about it and will stay away from that engine. The F300 is known to be one of the best outboards ever made. That is why we are leaning towards it (over the Suzuki 350)

A3: the plate says 400-HP max. But it is weird: I contacted Boston Whaler. Because the 2002 version says 400 max. But the 2003 and newer models say 450-HP. And Boston whaler said there was no changes made to the hull. Just that they did more testing and found out it could handle more. I'm not sure what that means for my 2002. Does that mean I am stuck at 400-HP?

biggiefl
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Re: 255 CONQUEST Re-power

Postby biggiefl » Tue Jul 30, 2019 2:18 pm

Over 22-feet [actually over 20-feet; see below--jimh] there is theoretically no max power rating as far as the Coast Guard goes. Some manufacturers still specify however.

Suzuki makes a hell of an engine. I have owned seven (I believe) and none have ever been to the dealer for a repair.

I believe Yamaha has fixed the flywheel problem but not sure how that works for those who own the older model.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

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Re: 255 CONQUEST Re-power

Postby jimh » Tue Jul 30, 2019 3:28 pm

Ratking20 wrote:A2: the Yamaha F350 is the engine with the flywheel problems. I know about it and will stay away from that engine.


Good decision.

Ratking20 wrote:A3: the [2002 boat] plate says 400-HP max....I contacted Boston Whaler....the 2003 and newer models say 450-HP...


Boston Whaler has changed the rated maximum horsepower for a hull in various years before. I think the change, usually to more horsepower, may be related to exactly what engines are available from Mercury. In the case of the 255 CONQUEST and c.2003 as an epoch change, I believe the circumstances were as follows:

  • Mercury had no four-stroke-power-cycle outboard engines in the 200-HP or higher range; their biggest FOURSTROKE back then was probably a 40-HP
  • the OptiMax was getting a bad reputation for reliability; customers were clamoring for four-stroke-power-cycle engines
  • Mercury made a deal with Yamaha to buy 4,000 225-HP Yamaha F225 engines, paint them black, and re-badge them as Mercury engines, in order to be able to offer customers of larger boats the option of a big four-stroke-power-cycle engine or even big twin engines

With the deal in place for the 4,000-units of 225-HP engine, a change in the rating of a big boat like a 255 CONQUEST to have a 450-HP limit instead of a 400-HP limit may be understood by the exigencies of that era. If Mercury has a warehouse full of 225-HP engines, you need some boat transoms that can use them.

Ratking20 wrote:Does that mean I am stuck at 400-HP?


I believe that Boston Whaler will NOT provide you with a new capacity place for your 2002 model 255 CONQUEST that says 450-HP.

As mentioned above, the USCG does not really inspect or enforce horsepower limits on boats longer than 20-feet, as that is the federal regulation. For more advice about this topic, see my article in REFERENCE.

Maximum Rated Horsepower
http://continuouswave.com/whaler/reference/ratedHP.html

Ratking20
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Re: 255 CONQUEST Re-power

Postby Ratking20 » Tue Jul 30, 2019 5:50 pm

Interesting. I did not know that about HP ratings. Does that mean i can not get in trouble in any way? With my Insurance company? If i go over 400—I probably will not.

I do like the Suzuki 350. My dad likes the Yamaha better. It’s his money. --I laugh aloud--

As for the Yamaha 350, my Yamaha dealer said it is probably coming off the market. The fix for the flywheel problem was that Yamaha would swap the part every 100 or so hours free of charge. Pain in the butt. Not for me.

In looking at numbers with my [255 CONQUEST] hull and a VERADO 300, can I assume similar results with the Yamaha F300?

What difference can I expect with the higher displacement of the Yamaha F300?

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Re: 255 CONQUEST Re-power

Postby jimh » Tue Jul 30, 2019 8:50 pm

The VERADO FOURSTROKE 300 is a beast engine. The Yamaha will be pressed hard to match it.

Ratking20
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Re: 255 CONQUEST Re-power

Postby Ratking20 » Tue Jul 30, 2019 8:55 pm

I only ask [about the equivalence of the VERADO 300 and the Yamaha F300 engines] because there are performance reports available for the VERADO 300 and a a few other Mercury engines on [255 CONQUEST] hull. [These Boston Whaler performance test results are the] only real world numbers i can find.

flymo
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Re: 255 CONQUEST Re-power

Postby flymo » Wed Jul 31, 2019 6:53 am

Yes, the performance of the Yamaha F300 will likely be similar to that of the Verado 300. It's the classic battle: larger displacement or forced induction. And people will be debating it forever. But both seem to work pretty well.

biggiefl
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Re: 255 CONQUEST Re-power

Postby biggiefl » Wed Jul 31, 2019 11:13 am

You will be in a close ballpark with the BW performance with the Verado. If you are fine with that, then go with the F300. If you think it could use more, talk to Dad about a Suzuki.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Ratking20
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Re: 255 CONQUEST Re-power

Postby Ratking20 » Wed Jul 31, 2019 12:59 pm

Thanks. My dad’s choice is the F300. My choice is the Suzuki DF350.

Of course [I am] younger and want more speed. But the main focus should be getting the boat on plane quickly.

With either the F300 or DF350 engine I will [expect to] see a [reduction in time to get on plane] from what we have now.

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Re: 255 CONQUEST Re-power

Postby biggiefl » Wed Jul 31, 2019 1:53 pm

With a 25' boat, speed is not that much fun. With a 25' boat my main concern would be economy which may improve along with the speed in your situation.

Fun is a 15' Whaler with a 90hp. Doing 50-MPH or faster in a 15' is borderline insane.

Fun is also a 16' Donzi as you can easily get into the 60's.

You are young; start saving your money, as you can never have just one boat.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

Ratking20
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Re: 255 CONQUEST Re-power

Postby Ratking20 » Wed Jul 31, 2019 2:47 pm

I also have a jet ski and a 13-footer with 40hp. You are right. One is never enough.

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Acassidy
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Re: 255 CONQUEST Re-power

Postby Acassidy » Thu Aug 01, 2019 5:14 pm

I know it is not the same boat but look at this 23' Outrage with Suzuki 300. That speed looks fun to me. I see more Suzuki 300s on the water in Galveston Bay than Yamaha 300s. This might be to the cost of repower.

https://www.youtube.com/watch?v=Y57MZeF2eJI&t=219s
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Ratking20
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Re: 255 CONQUEST Re-power

Postby Ratking20 » Thu Aug 01, 2019 10:33 pm

Looks cool. I don't need to go fast. Fast enough. And getting on plane fast is what is needed.