Logo
FULL SITE MENU

mercruiser 5.7 L smallblock RMP to high how to proper adjust?

P

pascalmekkelholt

Member
goodday,

i have a question, our engine had a few problems last months wont start nothing, most of the problems are solved, whe replaced most parts of the eninge, bobine, circuitbreaker, new bougies, fuelpomp etc, and cleaned the carburator total it whas a total mess inside, of the fuel it got, i live in the EU Netherlands, i fueled the boat whit E10 bio grade feul, last time i did that, i totally messed up the engine not runnning good any, now whe cleaned it all etc and just need to readjust the enginge rpm and fuel, whe thought it whas good when whe where testing on water when the engine whas on running temprature for adjustment, the RPM whas good around 800 RPM idle Warm engine, now 2 days later when i restarted the engine cold, the RPM goes to 1350 RPM idle, and it wil not drop, is it just to readjus the rpm screw or idlemixer on the carburator, or perhaps on the gas throttle cabel on the block?

greetings pascal, Netherlands
 
pascalmekkelholt said:
goodday,

i have a question, our engine had a few problems last months wont start nothing, most of the problems are solved, whe replaced most parts of the eninge, bobine, circuitbreaker, new bougies, fuelpomp etc, and cleaned the carburator total it whas a total mess inside, of the fuel it got, i live in the EU Netherlands, i fueled the boat whit E10 bio grade feul, last time i did that, i totally messed up the engine not runnning good any, now whe cleaned it all etc and just need to readjust the enginge rpm and fuel, whe thought it whas good when whe where testing on water when the engine whas on running temprature for adjustment, the RPM whas good around 800 RPM idle Warm engine, now 2 days later when i restarted the engine cold, the RPM goes to 1350 RPM idle, and it wil not drop, is it just to readjus the rpm screw or idlemixer on the carburator, or perhaps on the gas throttle cabel on the block?

greetings pascal, Netherlands
Click to expand...
The RPM shouldn't increase because of the gas.

Stop throwing money away by replacing parts that aren't bad- all of this can be diagnosed, you just need to do the diagnostics.

Take a fuel sample. If you have an electric fuel pump, test the pressure. As MakoMark posted, find a vacuum leak, but make sure the throttle is closing as far as it should, in order for the idle speed to be correct (~650-700RPM, not 800).

What was the air temperature when the RPM was at 1350 after starting? That sounds like it was in 'high idle', as it would when the temperature is very cold- check the carburetor linkage.
 
makomark said:
sounds like a vacuum leak....i would start by finding the leak and them fixing the leak
Click to expand...
I askes also a boatshop and they said exactly the same. De cause properbly is de gasket wrongly placed on the carburator and on the manifold. Going to change it and test it again. Thank you for your answer
 
Back
Top