How did I lose 10 MPH?

[Terry H]

spun prop?

 

[ebsworj]

How did I lose 10 MPH?

I took the boat out yesterday and I noticed she would only do 32-35 mph. Usually I can get here to 44mph w/ trim adjustments. Its a 120 HP OB on a 18' bowrider. 2 weeks ago i ran into a little submerged sandbar in the sound at slow speeds. The prop tips got polished but I don't see any visible bending or warping. It almost seems like the throttle cable slipped or somthing since it dosen't seem to rev up like it used to. Any ideas how to check if the throttle cable came out of adjustment? What to do?

 

[roscoe]

Re: How did I lose 10 MPH?

Speed trap got you and took your 10 mph. <br /><br />Don't be embarrassed to tell us you have a Force motor. <br />Be proud of it, it still runs don't it? <br /><br />I would say you are running weak on one cylinder.<br />So check the compression ( gauges are $29 at Sears or NAPA) , and the spark, and for gas to each cylinder. I bet you will find either no spark or low compression on one cylinder. <br /><br />What do the sparkplugs look like? Do they all look the same?<br />What year is this motor?<br />How high are the rpm going?<br />How is the holeshot?<br /><br />Could be just a head gasket or a bad coil, or it could be a lot worse.<br /><br />Let us know what the compression readings are.

 

[ebsworj]

Re: How did I lose 10 MPH?

Ok I'll check the compression... I'm somewhat scared to do that since I don't have the funds to fix a major outboard issue.<br /><br />The motor seems strong though. Holeshot is good. It has been idling a bit high lately also. <br /><br />Wouldn't i notice a lot of vibration if it was running on 3 cylinders?

 

[LubeDude]

Re: How did I lose 10 MPH?

Maybe the prop lost some of its pitch in the sand.

 

[TOHATSU GURU]

Re: How did I lose 10 MPH?

Check the double bottom of your boat for water if the engine turns out ok.

 

[AMD Rules]

Re: How did I lose 10 MPH?

Bent prop shaft?

 

[umblecumbuz]

Re: How did I lose 10 MPH?

Might sound kinda basic - but you haven't told us what revs you got before and after the bump.<br /><br />If they've dropped, that's the reason for your loss of speed.<br /><br />Have you got a rev counter? What does it tell you?

 

[jtexas]

Re: How did I lose 10 MPH?

Yeah, what about RPM's? Maybe the trim unit took some damage & won't trim out when you apply power?

 

[phatmanmike]

Re: How did I lose 10 MPH?

are you dragging a 1976 f150 behind you?

 

[ebsworj]

Re: How did I lose 10 MPH?

I wish i could tell you my RPM's! I bought a new gauge set when i got the boat (it didn't have a tach) but I haven't wired in the sender wire for the tach. I know for certain that the engine is not reving up as much as it used to. Its strange this happend in the span of a week. But it sounds likly that I may have a ******* cylinder... I have my fingers crossed for when I check my plugs this evening. What will the plug look like if its cylinder is low on compression?<br /><br />The trim works, i don't know if its damaged or not. <br /><br />No F-150... unless its invisible

 

[JB]

Re: How did I lose 10 MPH?

ebsworj.<br /><br />If you will just identify your engine I can move this thread to the proper forum

 

[ebsworj]

Re: How did I lose 10 MPH?

Sorry... It started off so inocently <br /><br />1994 Force 120

 

[JB]

Re: How did I lose 10 MPH?

To Force Troubles.