30hp efi revs up dangerously

[Timestep]

I have a 2004 Mercury 30hp efi on my 1989 15' SSL Boston Whaler. In the river here, at around 2,500rpm, shut the throttle to come into moor, and the revs temporally rise to 3,500 causing great problems ! It basically does this at all other rpms if you "quickly" close the throttle. The dealer says bring it back, but it's a 250 mile trip each way. I'm electronically and mechanically literate, any ideas folks ?<br /><br />Thanks<br /><br />Dave

 

[rickdb1boat]

Re: 30hp efi revs up dangerously

Don't know, but I'd make the trip...

 

[tashasdaddy]

Re: 30hp efi revs up dangerously

make the trip it is under warranty, and what you do could void the warranty. especially if it is a big problem.

 

[Timestep]

Re: 30hp efi revs up dangerously

I could, but I'm looking for some help here ?<br /><br />Dave

 

[Silvertip]

Re: 30hp efi revs up dangerously

Idle on an EFI engine is controlled in part electrically by a throttle position sensor which works like the volume control on your radio. More throttle, more the sensor turns, ECU gives the engine more fuel. At idle, the engine may also have an idle air control motor which allows air into the intake to provide smooth idle when the throttle plate is fully closed. Either or both of those systems may have a problem. Check for a loose vacuum hose that would allow extra air into the intake. If you are mechanically and electrically challenged as you indicate, any suggested electrical checks may be out of your comfort zone especially if you don't have a service manual specific to your engine.

 

[Timestep]

Re: 30hp efi revs up dangerously

I'm "very" good at mechanics and electronics and I have the manual. I'll look for the vacum hose, any other sugestions guys ?<br /><br />Thanks<br /><br />Dave

 

[Dunaruna]

Re: 30hp efi revs up dangerously

You need to read the codes first and foremost.<br /><br />There ain't no way around it.

 

[Timestep]

Re: 30hp efi revs up dangerously

I was hoping a Mercury Technician would give some guidance. I'm committed to Mercury, can you suggest a code reader, where to buy and how much ?<br /><br />Or from the symptoms, can anyone tell me what it is ? It's only an engine after all ?<br /><br />Thanks<br /><br />Dave

 

[Dunaruna]

Re: 30hp efi revs up dangerously

Only an engine, yes, but complicated components living together and taking orders from a computer.<br /><br />Last week I diagnosed a problem with a car that kept stalling, couldn't fault the components individually (all tests o/k). The eventual problem was the battery, not enough reserve capacity, when it dropped below 12.4v the computer started doing funky stuff. My point is, gone are the days of "off the cuff" diagnostics, complicated electronics require complicated gadgets to find simple problems. <br /><br />Do you have the genuine manual? Mine (50hp) is very detailed and the diagnostic procedures are very well laid out but you need the code reader, and diagnostic tester (mercurys answer to a DVM), both of which are only available through mercury.<br /><br />Bite the bullet, take her back to the dealer.<br /><br />Sorry.

 

[orca]

Re: 30hp efi revs up dangerously

G,Day<br />Something as simple as incorrectly adjusted cables can cause problems. With the motor not running, Lift the cover and have someone operate the throttle (I presume that the motor has forward controls0, observe while the throttle is pulled back to idle, check that the throttle lever comes back hard against the idle stop.<br />Unfortunatly just about everything on these motors are computer controlled, there is very little that can be checked without the correct diagnostic tool.

 

[Dunaruna]

Re: 30hp efi revs up dangerously

BTW, ANY merc dealer should be able to look at it (under warranty), not just the one you bought the motor from.

 

[Timestep]

Re: 30hp efi revs up dangerously

"check that the throttle lever comes back hard against the idle stop."<br /><br />OK, geting somewhere, how hard is hard ?<br /><br />"correct diagnostic tool" is there a cheaper clone ?<br /><br />Dave