Hard Start 3.0L Mercruiser - Maxum Boat Owners Club

bluedeuce · 07-12-2011, 07:02 PM

Hi, I have a 2008 1800mx with a 3.0L Mercruiser. I had a problem with the engine desieling when shutting off. The dealer replaced the thermostat to correct the problem. That has fixed it, but now it is hard to start hot or cold. I must use the choke to start. When it does start, it runs ok untill I try to put it into gear, then it will stall. Any suggestions....

seapuppy · 07-12-2011, 08:15 PM

welcome to the zoo...could be a number of things....first I'd check to see if you have a vacuum leak around the carb...that's usually the culprit....then start looking to see if the choke is working properly....is this an mpi (multi port injected) engine???...
it could be just bad gas.....lots to think of..

SP

bluedeuce · 07-12-2011, 11:44 PM

It is carburated.

bluedeuce · 07-13-2011, 12:00 AM

The boat runs great when it starts, just when I go to put into gear it will stall. It runs great for fishing, skiing, wakeboarding, just going from high idle to gear it will stall. It is also hard to start when the choke is not on.

seapuppy · 07-13-2011, 02:39 AM

ok...this sounds like a vacuum leak might be a problem...but...the choke is an issue..so...in a cold start...are you pumping the throttle 3 times in neutral and setting it to 1/4 fwd throttle???

when was the last time you had a full up tune up??...

is the gas fresh and fuel filter fresh and clean??

a few things to check

SP

robhemond · 07-11-2013, 03:22 AM

My boat does exactly same thing. Done it since it was new.. was it a vacuum leak?

vffb507 · 07-25-2013, 04:13 PM

On my older (97) as long as it was wrmed up nice it owuld be fine and not stall. Don't let it warm up and it would stall for sure. Also as seapuppy said, you must pump a few times and start at part throttle.
To check for vacuum leak try listening around engine for hissing noises though.

mmwjr · 07-25-2013, 05:08 PM

Boats don't have vacuum lines. Only source of leaks would be the carb gasket between the card and intake, intake gasket to head, or within the carb. The first 2 can be checked by lightly spraying these gaskets with a fine mist of water. The ater will temporally fill the gap and the engine's idle will smooth out. No easy way to test carb other than rebuild and see if it fixed the problem.

Several things have been discussed in this tread, what is the exact symptom you are having?