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700 lb Gas, 1000 lb People = Won't Plane!


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Recently bought a 2007 Sig 290. Two Volvo 260hp engines. Super clean and well maintained. I thought I would love it.

I'm kinda new to boating, having owned a 19-ft Bayliner many tears ago. But disappointment settled in when I gassed up and loaded several people on board. At full power the boat would not get on plane (props full down, trim full down). Plowed thru the water for well over minute and I was about to give up when it slowly started to get up on the water. Once on plane everything was fine. But what the heck? This thing should get itself going with no problem, right?

Is this to be expected? Please tell me I have a problem that can be fixed. I appreciate any suggestions.

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State the rpms of EACH engine. I would NOT TRUST the boats tachometer gauges until checked out.    Water temperature of engines . Also a HAND HELD    GPS MPH reading.  What size are the engines ? what series ?  Where do you buy the gas ? Marina  ?  People ahead of you may have put on the wrong or had the props TUNED  incorrectly

  Engines have had ALL  ignition  & fuel system old enough parts replaced in the last 50 hours ?   Could be cleared up with a FULL Maintenance  job.  It does happen. 

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Is there any drive lower gear case corrosion at the intersection between the front of the prop hub ring and the drive itself? missing metal there allows exhaust gasses to sneak out and ventilate the prop resulting in greatly reduced thrust. Also, what is max achieved RPM? Could have a prop bushing slipping but I doubt it as it would have likely given up all together by now.  W

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I had the same boat with twin v6 225 hp and with full gas water and 4 adults..(2 fatties) it planed fairly quick.

Try taking the boat out yourself and see how it runs.

I actually agree with clops....scary.

You may want to have your props tuned.

As you are a new owner a full maintenance will give you a baseline.

Good luck, this will get fixed and you will enjoy the boat.

.

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On 10/14/2020 at 5:38 PM, Wingsy said:

At full power the boat would not get on plane (props full down, trim full down). Plowed thru the water for well over minute and I was about to give up when it slowly started to get up on the water. Once on plane everything was fine.

Try a different approach: set the drive to various positions between 50-75% down, where 50% is the floating boat level. Keep the tabs all the way down as you had them. A boat needs forward thrust and speed to plane, and the drives all the way down try to lift the stern at the cost of forward thrust and speed. Let the tabs do the lifting. The faster the boat goes the more lift tabs will generate. Once on plane with a reasonable load and under normal conditions, set the drives to be more less parallel to the boat's forward motion. Keep adjusting up and down till you hear the engine running smoother and the RPM getting higher aka a sweet spot.

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I forgot the most important thing.

How level is the boat when everybody is in it ? have someone .............OUTSIDE............. the boat look at the boat and guide you to ORDER PEOPLE TO SHIFT AROUND to level the boat .

Too much weight bow or stern will cause that problem to get on plane.....Fast enough.......... USCG used to use 10 people. EACH ONE was 135 pound weight.   

My 2002 186 SSI with 5.0L V8 Could not lift up 6 + 200 pound seniors with the heaviest on the bench seats in 3 to 4 foot waves with the 50 mph prop on.  I put on a no Blow Out prop and a floored WOT start was a couple of seconds to a fast plane.   The PROP is super important with heavy loads.   I do not have any lifting plates..  I do jump into the water & change props for the load in the boat.  5 minutes at most with a Alpha . Single prop. drive. 

Dual props are a help.  But a single prop drive has UNLIMITED  Diameter , PITCH, CUPPING and rake available.

A twin engine boat should only have single props. 

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Any chance the boat is full of water? How did the boat run when you tested it before buying? Can it get on plane easily when lightly loaded?  Engine RPM  and speed data is needed.  This boat with twin 5.0 ‘s should be able to plane easily. 

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3 hours ago, cyclops2 said:

I forgot the most important thing.

How level is the boat when everybody is in it ? have someone .............OUTSIDE............. the boat look at the boat and guide you to ORDER PEOPLE TO SHIFT AROUND to level the boat .

Too much weight bow or stern will cause that problem to get on plane.....Fast enough.......... USCG used to use 10 people. EACH ONE was 135 pound weight.   

My 2002 186 SSI with 5.0L V8 Could not lift up 6 + 200 pound seniors with the heaviest on the bench seats in 3 to 4 foot waves with the 50 mph prop on.  I put on a no Blow Out prop and a floored WOT start was a couple of seconds to a fast plane.   The PROP is super important with heavy loads.   I do not have any lifting plates..  I do jump into the water & change props for the load in the boat.  5 minutes at most with a Alpha . Single prop. drive. 

Dual props are a help.  But a single prop drive has UNLIMITED  Diameter , PITCH, CUPPING and rake available.

A twin engine boat should only have single props. 

3-4 foot waves on a 18 foot boat and your trying to get on plane? Seems crazy. Not to mention they were seniors? 

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 I had a similar problem with my 2006 chap 276 w dual f-4 props and a single volvo 5.7 gxi... turned it I needed the injectors cleaned...  cost: 350 total. I could never get the RMs past 3800..  after cleaning, it revs to 5k and actually  had the boat up to 41.6mph the other day

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So there are at least 2 EXCELLENT  prop retailers to help you get the best props for a sluggish planning loaded boat.

Hill Marine or  Propgods.  call both for selection and  pricing.  Check out both of their TESTING of different props without buying everyone you want to test.

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Start out at a slower speed until you pick up a little speed then go full throttle. Full throttle at a dead stop buries the stern and lifts the bow and you will never plane. Most important is load distribution. Unless you want to spend money on new props. 

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I can positively state  That a prop built for thrust AND  grip / no slip.........  WILL keep my 2002 186 SSI  with a 5.0 V 8  PERFECTLY LEVEL from a  floored dead stop. There is NO  NO bow lift . 

The boat just starts level & stays that way to top speed.    Changing the trim angle DOES NOTHING to the level running  at any speed.

Most of us never learn about how important the correct prop is.

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