Top Speed 200hp Mercury

[muddasick]

Why on earth am I only getting 34mph tops from my 200hp mercury engine.

Could the throttle not be completely open?

Could the engine need servicing?

I'm really concerned.

Thanks

[Franco]

WHATS YOUR RPM, IS THE PROP CORRECT FOR THE BOAT? TRIMMED CORRECTLY?

[muddasick]

I just spoke to the guy who I bought it from and he said that he did change the prop to a heavier prop.

I have to check the RPM's I didn't take notice when I had it out Saturday.

Also Franco, when ever I start it the engine I have to hit it in gear as soon as the engine kicks in otherwise the engine will shut off. In other words it doesn't idle well. When I run the engine for a while and stop the engine will idle for about a minute then shut off??? What gives??

I'm new to boating, and appreciate the help.

Thanks

ps. How do you post images in your messages??

[Skools Out]

Check your throttle cable it may need to be adjusted to fix the idle issue or just turn the idle screw on the throttle linkage.

[bigshrimpin]

Mud - what year is your Mercury? also at 34mph what does your Tach read?

Before you go use the boat anymore you need to do a few things.

1. compression test - compression on those 2.4L merc engines should be around 115 - 125PSI (compression should not vary more than 10%)

2. Fix the elecrical problem. Take off the cowling and find the black wires with a yellow stripes. The black/yellow wires allow your key switch to kill the spark to your engine. There are two that connect to the switch boxes . . . make sure that the black and yellow wires are bolted down tight.
3. Get a Merc Service Manual (Ebay) . . . but clymers is "ok" too.

4. Clean your fuel delivery system . . . rebuild fuel pumps and carbs. (Also add a fuel water seperator and even an inline fuel filter if you don't have one)
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Figure out which carbs you have: These are wh-20's
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The carbs have a stamp on them right near the top

http://www.biggerhammer.net/mercury/wh20_top.jpg

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WH carbs aren't adjustable (at least mine aren't) and require rejetting to adjust the mix.

WMH carbs are adjustable.

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Good resources: for fixit stuff
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http://www.biggerhammer.net/mercury/
http://www.boatsetup.com
http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi

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more resources for tweaking your merc:
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http://www.screamandfly.com/home/engine_tech.htm
http://forums.screamandfly.com/forums/forumdisplay.php?f=20
http://www.byuboyz.com/forums/index.php?s=2034450ad67cc12a9c5139c5b5ef0fe5&

[bigshrimpin]

http://forums.screamandfly.com/forums/attachment.php?attachmentid=29264


Also check the black and yellow wire connected to the key switch.



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Mercury/Mariner Standard Outboard Wiring Color Code



Color Where Used / Function
Black All Ground
Brown Reference Electrode MerCathode System
Orange Anode Electrode MerCathode System
Lt. Blue/White Stripe Trim UP Switch
Lt. Green/White Stripe Trim DOWN Switch
Brown/White Stripe Trim Sender to Trim Gauge
Purple/White Stripe Trim "Trailer" Switch
Gray Tachometer Signal
Black/Yellow Stripe Shorting or Stop Circuit
Pink Fuel Sender to Gauge
Red Unprotected Wire from Battery
Red/Purple Stripe Protected (Fused) Wire from Battery
Red/Purple Stripe Protected (12 Volt +) to Trim Panel Control
Purple Ignition (Switch) to 12 Volt Positive
Tan Temperature Switch to Warning Horn
Tan Temperature Sender to Temperature Gauge
Tan/Blue Stripe Temperature Switch to Warning Horn
Yellow Starter Solenoid to Starter Motor
Yellow Starter to Regulator (Charging Circuit)
Yellow/Red Stripe Start Switch to Start Solenoid to Neutral Start Switch
Yellow/Black Stripe Choke (Enrichener System)
Green with Color Stripe Switch Box to Coil - Striped and Numbered
White/Black Stripe Bias Circuit (Switch Boxes)

The ABYC Recommended Colors



Color Where Used / Function
Yellow/Red Starting Circuits
Brown/Yellow or Yellow Bilge Blowers
Dark Grey Navigation Lights & Tach Signals
Orange Accessory Feeds
Brown Pumps
Purple Instrument Feeds
Dark Blue Cabin and instrument Lights
Light Blue Oil Pressure
Tan Water Temperature
Pink Fuel Gauge Sender

[bigshrimpin]

Mud - any luck with your motta?

[Seacrets]

Mud, check the pitch stamped on your prop. I have a 150 Merc and I turn a 17" pitch SS four blade prop and I turn 32 MPH @ 4000 rpm. I also have a 3 blade 17" pitch with pretty much the same performance.
Bob