350HP Mercruiser MPI Horizon's stalls

[jchoe98]

I need some advice. i'm a newbie and purchased a 2007 amberjack 290 (in 2010) which only had about 20 hrs.
No problems starting
No problems with idling
No problems with cruising

Problems of stalling when maneuvering at low speeds...i've been lobstering and at about the 9th trap (low speed maneuvering for about 30 minutes), my starboard engine will stall. then, i just use only my port engine for about 10-15 minutes and then whallah! the startboard will start again. but if i try to restart it before the 10 minute mark, it won't restart.

I've changed the oil filter, had a change change, and have burned through the old gas and put new gas with fuel/injector cleaners.

any advice for a newbie who's very frustrated and seeking sage advice?

 

[paulswagelock]

It happens after long low speed time, but to one engine. So, the fuel itself is not the problem since the other engine is fine. I would liook into fuel delivery issues since it works again after it sits. You have the cool fuel 3 system which is water cooled to keep from vapor locking. First, I would remove the cool fuel system filter and dump it looking for water (it is also your water separator). I would examine it and the screen (micron) filter below it. With low hours they should not need replaced, but can't rule that out. Reassemble the filter assembly, and give it a sea trial. If the problem persists, I would next look at the water circulation loop to the cool fuel module. If it is restricted, you will vapor lock the engine.

 

[capecodcruiser]

Idle air control valve. I need to do mine as well for the same symptoms.

 

[Go Aweigh2452]

Paul and Cape both have excellent suggestions.

The disk under the paper filter catches the gunk and could be clogging when no load is put on the fuel pump which basically starves the engine. Another thing to check is the fuel hoses. Squeeze them and feel for sponginess or hardness as you pinch them. Could be some latent E10 issues if it was ever filled with the stuff. It can go bad rapidly in our tanks since they are open to the air unlike cars.

IAC valve could be failing too. Not a biggie to change it out or at least have a spare.

Another resource is to call a Merc and ask for the Horizon rep and hear what he/she has to say. Or call your local Merc dealer and ask to speak to the person that knows the Horizon system...

 

[jchoe98]

thank you everyone for your wise advice. I will first learn how to and change the idle control valve and see if it fixes the problem...after which, i will post a second reply to let you know if it worked. thanks again!

 

[Presentation]

thank you everyone for your wise advice. I will first learn how to and change the idle control valve and see if it fixes the problem...after which, i will post a second reply to let you know if it worked. thanks again!

It is part number 14

Change the filter #12, gasket #8 and IAC # 14. The filter goes inside the throttle body assembly. Remove the engine cover and flame arrestor, you will see it on one side of the throttle body assembly. Pull out the old filter, shove in the new filter.

Get your engine serial # off the engine cover. Go here and enter your engine serial number. Look at the drawing labeled throttle body assembly to get the correct part numbers. This is a Mercury owned website
http://www.mercurypartsexpress.com/us/

With the correct part numbers just Google the parts to find the best price. You sould find these for under $100 total.

Photo from www.boats.net

 

[flflatrate]

you should of tried when it wouldn't start to advance the throttle and start it. If it started its probably the iac. if it didn't it could be the cool fuel module getting hot. You can feel the side of the fuel module compared to the motor that is still running and see if it is allot hotter. If it is your water hoses that go into the module are clogged which I see allot.