Does anyone know why my boat isnt picking up speed?

[sthao7]

I have 1987 marlin with a 3.0L omc cobra motor and dont know why it takes soo long for it to pick up speed. after a few of miles of driving, then it'll start picking up speed. can anyone help or know whats the problem?

 

[Bondo]

Re: Does anyone know why my boat isnt picking up speed?

Dirty Fuel Filters,..??..??...

 

[180shabah]

Re: Does anyone know why my boat isnt picking up speed?

Need more info

What is your current WOT RPM?
Exactly how long is it taking to go from X RPM to Y RPM?
Is you engine healthy, Have you done a compression test?
Fuel filters already mentioned.
Is the Gas itself good?


ALSO, There is no need to start a new thread if you don't get an answer as fast as you would like.

 

[Windykid]

Re: Does anyone know why my boat isnt picking up speed?

Has it had a tune up?

 

[sthao7]

Re: Does anyone know why my boat isnt picking up speed?

Has it had a tune up?

I just bought the boat a week ago. i asume no it hasnt had a tune up.

 

[sthao7]

Re: Does anyone know why my boat isnt picking up speed?

Need more info

What is your current WOT RPM?
Exactly how long is it taking to go from X RPM to Y RPM?
Is you engine healthy, Have you done a compression test?
Fuel filters already mentioned.
Is the Gas itself good?


ALSO, There is no need to start a new thread if you don't get an answer as fast as you would like.

it takes about 10 minutes to get from 2000rpm to 3500 rpm. i havent done a compression test. the fuel filter seems clean to me.

 

[Windykid]

Re: Does anyone know why my boat isnt picking up speed?

Start with a compression test to see where the motor is at. Post findings.

Check the condition of the plugs and let us know.

 

[180shabah]

Re: Does anyone know why my boat isnt picking up speed?

I am assuming (I know.....) that your boat is not on plane at 2K and is at 3.5K, so it is struggling to ontop of the water. There are alot of possibilities, after you have done a compression test and full tune up I would look at the gear ratio in the drive and then the pitch and number of blades on your prop. It may just be a case of being overpropped, who knows what the PO may have done.

 

[sthao7]

Re: Does anyone know why my boat isnt picking up speed?

xcf

 

[sthao7]

Re: Does anyone know why my boat isnt picking up speed?

I am assuming (I know.....) that your boat is not on plane at 2K and is at 3.5K, so it is struggling to ontop of the water. There are alot of possibilities, after you have done a compression test and full tune up I would look at the gear ratio in the drive and then the pitch and number of blades on your prop. It may just be a case of being overpropped, who knows what the PO may have done.

I just recently replaced the prop and the person said that my old prop was for more of a slow speed boat like a patio. i forgot how much pitch was it but i changed it to a 13.2"x19" pitch. could that be the problem? do u happen to know the gear ratio it should be on?

 

[Don S]

Re: Does anyone know why my boat isnt picking up speed?

Is this your first boat? Are you using the trim properly?

 

[sthao7]

Re: Does anyone know why my boat isnt picking up speed?

Is this your first boat? Are you using the trim properly?

yes this is my first boat. im not sure if im using the trim properly. the trim is all the way up.

 

[Don S]

Re: Does anyone know why my boat isnt picking up speed?

the trim is all the way up.

Hopefully you mean on the trim gauge, and not tilted all the way up?
You need the prop in the water

 

[Don S]

Re: Does anyone know why my boat isnt picking up speed?

Here is a link to a Mercruiser owners manual. On page 32 is a section on trim and tilt and how to use it. Plus some other information in the manual you may find helpful.
http://www.boatfix.com/merc/Owner/gas/86017101.pdf

For best speed and planing ability, using the trim is something that is done constantly to keep the boat in best trim.

 

[180shabah]

Re: Does anyone know why my boat isnt picking up speed?

yes this is my first boat. im not sure if im using the trim properly. the trim is all the way up.

OK, when starting out your trim should be all the way DOWN

With a 4cyl, the gear ratio in your drive should be in the neighboehood of 2:1 and would probably make your 19" prop a good starting point.

Try readjusting the trim and see what happens.

 

[sthao7]

Re: Does anyone know why my boat isnt picking up speed?

Hopefully you mean on the trim gauge, and not tilted all the way up?
You need the prop in the water

yes thats what i meant. how do you use the trim properly? newbie

 

[180shabah]

Re: Does anyone know why my boat isnt picking up speed?

There is your problem

 

[180shabah]

Re: Does anyone know why my boat isnt picking up speed?

Is this your first boat? Are you using the trim properly?

I guess this is why Don is the professional, we are trying to fix it, and it isn't even broke.

 

[Windykid]

Re: Does anyone know why my boat isnt picking up speed?

Here you go, this may help!

http://forums.iboats.com/showthread.php?t=191939&highlight=proper+trim

 

[WAVENBYE2]

Re: Does anyone know why my boat isnt picking up speed?

I am also a newbie , I also had to learn how to use my trim & tilt properly last season.Listen to these guys they really know what they are talking about, down load all the manuals you can they give you , I would still be lost big time if it weren't for this site...I'm still a newbie, but a learning newbie
QUOTE : If i wasn't frustrated , I would feel like nothing was accomplished !!
Knowledge is only half the battle !!