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Hammer2o

MOST - 2004 298 SS top speed

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As stated in the title, I have a 2004 298 SS with a pair of 300hp Mercruiser 350 Mag MPI Horizon's. Every review I read has the boat at mid 50's to low 60's. My friend has a 2007 with a pair of 320 hp mercruiser, I was on that boat with 9 people doing over 60 mph.

 

Boating magazine hit 57.8 mph with 280 hp volvo's. http://www.boatingmag.com/monterey-298-shock-therapy

 

I have Bravo 3 drives and stainless steel 24P props.

At WOT and trimmed, it's at 4,400 rpm's.

The top speed is 46 MPH on GPS.

 

Why would I be off over 10 mph with 40 more horsepower.

 

Thank you for your help.

Jim

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If I can EVER remember to take my handheld GPS out I will make a top speed run yet this fall and let you know. You have me curious too. Honestly we rarely ever run over 40 (per the speedo) on Lake of the Ozarks, it's just far too busy and rough when we're down on the weekends. Usually have the tabs down, trim in and letting it eat at about 30!

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Hello Hammer2o

 

I have attached a performance report for you.

 

It would be a good idea to have your engines checked by a certified Mercury technician. It could be something simple. Also, make sure the tach's are synchronized and you are getting a true reading on a GPS for speed in case it is a gauge issue.

298SS Merc 350MAG B3 16Jun06.pdf

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MOST,

Page 1 shows 350 MAG 300 HP motors, page 2 shows 320hp under Boat Specifications and 300hp under Engine specifications.

 

Do you know which one is correct?

 

Jim

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MOST,

Page 1 shows 350 MAG 300 HP motors, page 2 shows 320hp under Boat Specifications and 300hp under Engine specifications.

 

Do you know which one is correct?

 

Jim

Hi Jim,

 

On page 2 the section called Boat Specifications, T-320 is the max horsepower rated for the boat model.

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The document shows 28P props, my survey shows 24P props, could that be causing the lack of RPM's?

 

Jim

 

Hi Jim,

Not neccesarily. Prop selection is also based on the gear ratio of your outdrive, what you use your boat for and the alitude that you boat in. It would be a good idea to get the advice of a certified Mercruiser tech and also make sure the tach's are synchronized. Also confirm that you are getting a true mph reading on a GPS for your speed in case it is a gauge issue.

 

There is a prop selector on the Mercury website as well: www.mercurymarine.com

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With the bimini top up, just me in the boat, 1/2 tank of fuel, some wind swirling...I got 54.5 mph on GPS. I have the 2005 with Twin 350 Mags. Tach's indicated just over 5000 RPM.

 

I would imagine with the bimini top off and some tweeking on the trim, no wind, etc. 57-58 would be possible. It will run 52 VERY strong without pinning it! Getting that extra 5 mph takes a lot of effort. As I said above, I haven't had the boat over 40 most of the summer! It was fun to go out and open it up on some "normal" water.

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With the bimini top up, just me in the boat, 1/2 tank of fuel, some wind swirling...I got 54.5 mph on GPS. I have the 2005 with Twin 350 Mags. Tach's indicated just over 5000 RPM.

 

I would imagine with the bimini top off and some tweeking on the trim, no wind, etc. 57-58 would be possible. It will run 52 VERY strong without pinning it! Getting that extra 5 mph takes a lot of effort. As I said above, I haven't had the boat over 40 most of the summer! It was fun to go out and open it up on some "normal" water.

 

 

Thanks Sunrise!

Do you know what props you have on the boat?

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Hi Jim,

Not neccesarily. Prop selection is also based on the gear ratio of your outdrive, what you use your boat for and the alitude that you boat in. It would be a good idea to get the advice of a certified Mercruiser tech and also make sure the tach's are synchronized. Also confirm that you are getting a true mph reading on a GPS for your speed in case it is a gauge issue.

 

There is a prop selector on the Mercury website as well: www.mercurymarine.com

 

 

Thank you for the reply.

The speed was from a GPS, I had a survey done on the boat when I purchased it recently, he had diagnostic software hooked up to the engines, at full throttle the tachs indicated 4,400 RPMs and the software showed 4,400 on one motor and 4,410 on the other.

I guess I have to find a tech to try and figure the prop situation out.

Jim

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Thank you for the reply.

The speed was from a GPS, I had a survey done on the boat when I purchased it recently, he had diagnostic software hooked up to the engines, at full throttle the tachs indicated 4,400 RPMs and the software showed 4,400 on one motor and 4,410 on the other.

I guess I have to find a tech to try and figure the prop situation out.

Jim

 

 

What stock props would come from the factory when the boat was purchased new in my area (Long Island, NY)?

 

 

Thanks

Jim

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