highhplowiq

256 SSI and 6.2L power

16 posts in this topic

You guys with a 256 and the 6.2L, do you feel like the power is adequate?  If I have 3/4 or better tank full of fuel and a few guests in the back the boat will flat not plane out.  I know that is a lot of undistributed weight but still I would expect it to get on plane eventually.  I can't decide if the motor is down on power and I need to start chasing issues or if that's just the nature of a big heavy boat and 320hp motor.  With even weight distribution the boat feels fine for the most part.  It's no power monster but it gets the job done.  Just looking for opinions.

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think your going to have to give MPH at full throttle and speed, and speed by GPS is possible.  hard to know what you are experiencing without numbers, you have an engine issue, or could be your expectations are wrong dont know. 

 

Are you starting with the drive all the way down and as you gain speed, trimming up?  Does the boat sit in the water, if so is the hull clean, if not clean with a bunch of growth can slow you down.  Have you checked the bilge to make sure not a ton of water is in there.  Also whens the last time you had a tune up; new plugs, cap&rotor, and wires?  Fresh fuel filter.

 

I can tell you on my 2002 265SSi with a 5.7 GXI (320hp) same hp as yours probably a little less torque, I could get to 45mph ish and around 4500-4600 RPM, with 4 people.  I would think light load your boat should hit 4500-5000rpm and 45-50mph.

 

To be honest though with these 25-26ft boats weighing what they weigh with small blocks in them, the performance factor on them is not going to be great.

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3 minutes ago, soldier4402 said:

think your going to have to give MPH at full throttle and speed, and speed by GPS is possible.  hard to know what you are experiencing without numbers, you have an engine issue, or could be your expectations are wrong dont know. 

 

Are you starting with the drive all the way down and as you gain speed, trimming up?  Does the boat sit in the water, if so is the hull clean, if not clean with a bunch of growth can slow you down.  Have you checked the bilge to make sure not a ton of water is in there.  Also whens the last time you had a tune up; new plugs, cap&rotor, and wires?  Fresh fuel filter.

 

I can tell you on my 2002 265SSi with a 5.7 GXI (320hp) same hp as yours probably a little less torque, I could get to 45mph ish and around 4500-4600 RPM, with 4 people.  I would think light load your boat should hit 4500-5000rpm and 45-50mph.

 

To be honest though with these 25-26ft boats weighing what they weigh with small blocks in them, the performance factor on them is not going to be great.

I'll do a speed check this weekend.  Boat is exceptionally clean so no issues there.  It does not stay in the water either.  I come out of the hole with trim fully down.  No water in bilge.  Boat could probably stand for a tune up, I don't think I've ever done one and I've had it since 2009.  But then again, it has always ran great, just seems under powered.  I do have all the parts on hand to do the whole fuel filter system, just need to get in there and get it done.

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I guess this point it then boils down to getting some numbers.  Trim should be probably 1/4 of the way up at full speed give or take based on touch.

At this point until we know numbers it seems like its either a tune up and or expectations. 

If you've never done a tune up chances are when you bought it at 4 years old it never have one, so probably due.  I would do plugs, cap & Rotor, wires you can inspect and if they look brown or cracked then replace, if not maybe hold on to them.  Even with wires all the parts there are probably less than 100 bucks and an hour or two worth of work.  Just replace one plug at a time.  Then when you get to the cap and rotor, take the cap off leave the wires on if you can, leave it off to the side, replace the rotor, install new cap dont over tighten screws to crack the plastic.  Then one by one do the wires, you wont mix up the firing order that way, otherwise mark everything.  then new fuel filter with a few cans of sea foam, youll probably be alright.

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Plenty of power for that boat. It should plane without issues unless you invited Billy737's friends along...

brick

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Ah, Billy737 ... I miss the guy but not his friends ... :)

Back on the topic ... @OP ... Correct weight distribution is necessary, you can't fight physics.

Did you try to trim the drive to see if that helps? Do you have trim tabs?

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Long time members here will understand. 

brick

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22 minutes ago, brick said:

Long time members here will understand. 

brick

:yb624::yb624:

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No trim tabs.  I don't think the plugs have ever been changed.  I've added it to the list.

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the spark plugs will make a big difference.  boats are not like cars.  If not changed since 2009, I don't know what your normal operating RPM's are but you can check on top of the engine, should be a sticker that tells you all the Maint. items.  bad plugs can easily cost you power and WOT RPM's 

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3 hours ago, brick said:

Plenty of power for that boat. It should plane without issues unless you invited Billy737's friends along...

brick

Miss old Billy's pictures, always made me laugh!!

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On 5/19/2017 at 10:47 AM, highhplowiq said:

I'll do a speed check this weekend.  Boat is exceptionally clean so no issues there.  It does not stay in the water either.  I come out of the hole with trim fully down.  No water in bilge.  Boat could probably stand for a tune up, I don't think I've ever done one and I've had it since 2009.  But then again, it has always ran great, just seems under powered.  I do have all the parts on hand to do the whole fuel filter system, just need to get in there and get it done.

Rev range for the 320 hp MerCruiser 6.2L MPI / 377 Mag MPI is 4800-5200 at wide open throttle. Recommend the following:

8M0061335 - MerCruiser HVS style cap and rotor kit. Will need a Torx T20 screwdriver for the dist. cap screws, and a Torx T15 for the rotor screws. 

NOTEthe distributor itself is made of plastic, so care will need to taken not to break the plastic ears off that the dist cap mounting screws thread into when removing and installing the 2 dist. cap screws.

  • NGK ITR4A-15 Laser Iridium spark plugs. They're pre-gapped to 0.060"

 

  • Place your outdrive in the Bravo 1 position for faster hole shot with less bow rise. Will need to adjust your trim send trim sender on the gimbal ring to allow the trim gauge to read correctly for your particular model and year. Your drive is almost certainly in the factory Bravo 3 position which does not allow the drive to trim in as far. Have not found any adverse handling issues with any Bravo 3 equipped Chaparral's from using with the Bravo 1 position.

 

  • Time the props; found boats typically perform better with only 1 prop directly under the cavitation plate on the drive at a time. Will need a 1/2" nut for the prop anode bolt, and a 1 7/16" nut for the rear prop nut. Torque the rear prop nut to 60 lb-ft when re-installing the prop.

Image result for mercruiser cap and rotor kit

distributor.jpg

  • T2e6YXXe4XXXXXXXXX_!!409402689.jpgBravo1position_zpse77175c2.jpg
  • Image result for shepherd bravo 1 position
  • trim-sender.jpg

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Great info ^^^

 

Took the boat out this weekend with a full tank of fuel and just me on board.  It felt peppy and came out of the hole without issues.  Seems to be running well.  It could be I just had way too much weight in the back when it wouldn't plane out.  Couldn't check RPMs because my gauge was not working.  No idea why, I'll have to chase that down next.  Thanks for all the info given here.

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