only 18 knots at full throttle.

T

tigerhack

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i get 18 knots at full throttle well the boat i heard is 4550 pounds there was 4 person on board and the boat plain off at about 15 knots, what can i do to get more speed ? (mercrusier 5.7 litre 350 hp , prop 15x17).
 
tashasdaddy

tashasdaddy

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Re: only 18 knots at full throttle.

you have a major problem somewhere. is this boat new to you? i have a 99 23foot deckboat with that weight and power. runs out at 40mph. have you checked compression, could be the hull is holding water in the foam. did you try triming the outdrive?????
 
Silvertip

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Re: only 18 knots at full throttle.

When was the engine last tuned? May be running on half its cylinders? Fuel tank contaminated with water or fuel that has gone bad. Carb may be due for rebuild. Dirty hull and as was mentioned, lugging around a boat load of water soaked foam doesn't help. You have gauges! What do they indiate? Water temp, oil pressure, volts, and tach (at wide open throttle).
 
Don S

Don S

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Re: only 18 knots at full throttle.

For one thing, you have an automotive distributor in your boat. Not sure about the carburator you have, the fuel system or anything. What was this engine when you put it in the boat? Is any of it marine?????

Your Pictures from the other thread
 
Don S

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Re: only 18 knots at full throttle.

Since you aren't getting full speed, I would assume you aren't getting full WOT (Wide Open Throttle) rpm specified for your engine, which should be between 4600 and 4800.
Here are a list of causes to go along with the already known issues.

List of possible causes of low WOT.

Engine Won't Reach Operating RPM. Check

  • Fuel condition. Type and Octane possibly old fuel
  • Propeller pitch or diameter, damaged blades
  • Restricted fuel pickup tube or anti siphon valve Fuel System Test
  • Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
  • Marine growth on hull and outdrive
  • Wrong gear ratio in outdrive
  • Restricted carburetor air intake (clogged flame arrestor)
  • Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
  • Poor cylinder compression Compression Test
  • Carburetor defective, or wrong type.
  • Fuel pump pressure and vacuum
  • Boat overloaded, improperly loaded, or improperly trimmed.
  • Engine Overheating
  • Engine timing and ignition system operation (Full tuneup done recently)
  • Remote control cables and linkage for proper travel to open throttle plates fully.
  • Tachometer accuracy.
 
Capt. Mike

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Re: only 18 knots at full throttle.

It sounds like someone changed the prop and put the wrong one on there. or you have dinged up your prop
 
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tigerhack

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Re: only 18 knots at full throttle.

i also notice the right riser run more warmer than the left one is that an issue ?
 
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tigerhack

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Re: only 18 knots at full throttle.

Silvertip said:
When was the engine last tuned? May be running on half its cylinders? Fuel tank contaminated with water or fuel that has gone bad. Carb may be due for rebuild. Dirty hull and as was mentioned, lugging around a boat load of water soaked foam doesn't help. You have gauges! What do they indiate? Water temp, oil pressure, volts, and tach (at wide open throttle).
Click to expand...

oil pressure 45 psi , engine temp 125 volts 13, tach just installed idle at 800 i will test wot later this evening. while the boat is in water.
 
180shabah

180shabah

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Re: only 18 knots at full throttle.

Your idle speed is too high - you need to bring it down around 650.


And there are some issues with the above pic.

Screw shoved in the end of the vac line on left side of carb?????

El Cheapo inline fuel filter....are the fuel lines marine rated???

Vac line to nowhere - from front of carb, just right of the fuel inlet. Is this even a marine carb????

Spring from the throttle linkage to a wire wrapped around the coolant hose. Why is it even there????
 

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Don S

Don S

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Re: only 18 knots at full throttle.

No, that is not a marine carb, you can see the automotive bowl vent just under the flame arrestor under that little metal cover. It works well with the automotive distributor.
Wrong advance, wrong fuel, no wonder it won't run right.
Plus, it's dangerous.
 
T

tigerhack

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Re: only 18 knots at full throttle.

Don i didnt know that is what i get with the engine,i have the old carbarator from the old engine lying around ,i will look for it .
 
Don S

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Re: only 18 knots at full throttle.

I think Capt Jason's signature line works here.

"just because you found it that way... doesn't mean it's supposed to be that way. "
 
T

tigerhack

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Re: only 18 knots at full throttle.

It sounds like its better to buy a new engine then, it seems like this boat is a half automobile ,like some of the speed like on dry land, and i have to change all them parts ...how hard is it to bracket on 2 outboard engines ?
 
T

tigerhack

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Re: only 18 knots at full throttle.

Don S said:
I think Capt Jason's signature line works here.

"just because you found it that way... doesn't mean it's supposed to be that way. "
Click to expand...

i have found the old carbarator getting it rebuild , do you know how to route the vacuum from off the distributor (of course i am going to get a new distributor ) but i want to know the complete Vacuum route from the carbarator to the distributor.any specs on it would be good and what psi gas pump should i use .
 
Bondo

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Re: only 18 knots at full throttle.

Ayuh,......

Marine Distributers Don't use Vacuum....... So there are No vacuum lines......

The Fuel Pump should provide 4/ 6psi to the Carb.......
 
T

tigerhack

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Re: only 18 knots at full throttle.

Bond-o said:
Ayuh,......

Marine Distributers Don't use Vacuum....... So there are No vacuum lines......

The Fuel Pump should provide 4/ 6psi to the Carb.......
Click to expand...

so what is used to advance the distributer ?
 
Bondo

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Re: only 18 knots at full throttle.

Haut Medoc said:
Internal centrifugal weights.....;)
Click to expand...

Ayuh,......

Actually,... Your 1992 should have the T-Bolt IV system which is electronically controled.......
 
T

tigerhack

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Re: only 18 knots at full throttle.

Bond-o said:
Ayuh,......

Actually,... Your 1992 should have the T-Bolt IV system which is electronically controled.......
Click to expand...
Bond all of those was flooded by the greaT HURRICANE IVAN so i was left with nothing apart from the iv amplifier.
 
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