3.0 GS unclear noise coming from motor

passan

Recruit
Joined
Apr 18, 2015
Messages
2
Hi,

I'm having the following issue.
I have got a 3.0 GS engine, which i tested after it's wintersleep yesterday.
During the winterdays both bellows and prop were replaced for a 4 blade instead of 3 blade.
The engine ran fine for about 20 minutes, first we took it real easy, to get a good motor temperature
and then we took it to it's maximum rpm's for around 4600. Then suddenly a rattling noise came out
of the engine compartment and we shut the engine down. Since we were at drift on a busy river,
we had to take the boat to the harbour at almost idling speed. The motor will start normally and will take
up power if you max the throttle (i know it's very stupid, but i had to test it). The only thing you hear
is a sound, that sounds like air escaping somewhere at the manifold side or a high pitched knocking sound.
The sound increases at the frequency of a piston stroke, and there's a heavy fuel smell, like one cylinder
is not firing. Is it possible that the new prop, caused the motor to take too much rpm's which blew the
head gasket ?????? I monitored the motor temeprature the whole time and saw no overheating signs.

Anyone having an idea ???


Pascal
 
Last edited:

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Start with a compression test.
Start the motor and remove the oil fill cap. Check for excess air or blowby.
While the motors running, turn the wheel left and right,does the sound increase?
 

passan

Recruit
Joined
Apr 18, 2015
Messages
2
Boat has been to a marine repair shop, since the compression test failed.
Head gasket was blown.
After resurfacing head and replacing gasket, no problem anymore.
Thanks for the input.
 
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