Slipping - whats wrong?

[mattias]

We have a 2005 mercruiser 350 mag with a bravo 3 drive in our 240sd. When i get up to about 2300 rpm, it looses power to the motor - whats wrong?

 

[hughespat57]

Look you have to be a bit more precise in the description and as detailed as possible if you really expect a useful answer.

"2005 Mercruiser 350 mag with a bravo 3"
- good start, but to look up manuals and parts diagrams the serial number and model off the engine tag is very useful (red tag on cover over air intake)

"Slipping - whats wrong"
- when a prop or engine coupling "slips" the boat speed drops or will not increase BUT the engine revs up, sometimes very high, because it has no "load" on it.

"When i get up to about 2300 rpm, it looses power to the motor"
- so which is it?, is it slipping? or is 2300 the maximum rpm you can get out of the engine? (this is more often called "bogs down at 2300 rpm")

 

[mattias]

Thanks - not sure if it is slipping (although the RPMs are not reving up when it happens). Its losing power when i get above 2200 RPMs (its running fine till then). I know there is a low speed fiel pump and a high speed fuel pump. Does it sound like the high pressure pump?

 

[hughespat57]

Go slow, don't jump to throwing parts at it, that can get very expensive very quickly.

How long have you had this boat?
Is this a new problem? If yes when did it last run well?

Could a lack of top RPM be caused by fuel problems? Yes
How old is the fuel in your tanks?
When was the last time you changed the fuel filters? (often two, one near the tank, and there is one near or in the pumps)
What types of pumps and filters is why the serial numbers are important, cool fuel?, cool fuel 2?, cool fuel 3?

Do you have access to a fuel pressure gauge? (sometimes local parts stores will lend/rent these)

 

[Lenny3]

Sounds like you may have a Smartcraft gauge going into guard mode limiting your RPM's. Do you have a Smartcraft Gauge?

 

[mattias]

Yes, I do have a SmartCraft guage.

We bought the boat last season. We just had the fuel filter changed as well as a new impeller installed. We put a pressure checker on the valve and got no reading on it at all?

 

[Espos4]

Yes, I do have a SmartCraft guage.

We bought the boat last season. We just had the fuel filter changed as well as a new impeller installed. We put a pressure checker on the valve and got no reading on it at all?

If the engine starts and runs but your fuel pressure test gauge shows zero psi, the gauge may be defective or it may not be hooked up properly. The pin in the schrader valve must be depressed when the test gauge is installed.

 

[scoflaw]

Sometimes the schrader valve needs to be removed

 

[mattias]

Noticed just a very little leak in the Schrader valve and with it not showing any pressure, we ordered a new one to put on also...