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Old    Detox (bass10after)      Join Date: Feb 2010       04-15-2013, 9:46 PM Reply   
Got my boat last year with 340 hrs. Its at 390 now. Its a 99 mastercraft 230vrs with indmar ltr engine. (gm 5.7 liter same as malibu's monsoon 340) On the first start up when its cold it will start then die. Then i re-start it and it runs but idles rough and will die when put into gear(usually backing off trailer). If I start it and let it run for a couple min then put in gear it will stay running but will act like its going to die. After its warm putting the boat in gear has no effect on anything but does sometimes have a slight hesitation when applying throttle to take off. Last year had it checked at the local malibu dealer and they weren't able to find anything wrong. The compression is at factory specs for brand new engine, the plugs were changed, fuel pressure was checked and also is to spec, I changed the IAC valve as part of the elimination process, ran fuel system treatment through it as well. I'm not much of an engine guy but i'm capable of changing things if you guys have any suggestions. I don't know if i just have a cold blooded engine (is that even possible these days?) or an underlying problem but any input would be appreciated..
Old    9Drozd            04-15-2013, 10:48 PM Reply   
When just idling, listening to the motor, is it knocking pretty bad or running normally? If it is, check to make sure whoever winterized/dewinterized your boat, didn't disconnect the knock sensor wire.

Last edited by 9Drozd; 04-15-2013 at 10:53 PM.
Old    Detox (bass10after)      Join Date: Feb 2010       04-16-2013, 6:52 AM Reply   
Doesn't seem to be knocking at all..
Old    Robby Elliott (Elliottsx80)      Join Date: Feb 2012       04-16-2013, 6:56 AM Reply   
check for a vacuum leak. will be one of the rubber lines coming off the intake somewhere. i see that more than anything on boats. vacuum hoses get dry rotted and brittle and leak
Old    nEwJ_HoSeR (tinytdubb)      Join Date: Jul 2007       04-16-2013, 12:39 PM Reply   
Have you changed your fuel filter water/separator? Simple fix and a dirty one usually gives those exact symptoms.
Old     (madcityskier)      Join Date: Jun 2012       04-16-2013, 5:51 PM Reply   
X2 on the fuel filter. At that age injectors may also be an issue. Filter is most likely IMHO.
Old    Detox (bass10after)      Join Date: Feb 2010       04-16-2013, 8:56 PM Reply   
I'm not sure where the fuel water separator would be located on the ltr? I've been told the fuel filter is actually located inside the fuel tank with the actual fuel pump... But if it was the filter wouldn't the fuel pressure be low?
Old    Detox (bass10after)      Join Date: Feb 2010       04-16-2013, 9:12 PM Reply   
I also remember that the engine had a lean code when the mechanic had it on the scan tool but he didn't recognize what would cause that... I forget what the exact code is now its been a long year...
Old    Cory D (cadunkle)      Join Date: Jul 2009       04-17-2013, 6:36 AM Reply   
Quote:
Originally Posted by 9Drozd View Post
When just idling, listening to the motor, is it knocking pretty bad or running normally? If it is, check to make sure whoever winterized/dewinterized your boat, didn't disconnect the knock sensor wire.
I would be amazed if you could get an engine to knock at idle with no load. I don't think you understand what a knock sensor is.
Old    9Drozd            04-17-2013, 7:26 PM Reply   
Quote:
I would be amazed if you could get an engine to knock at idle with no load. I don't think you understand what a knock sensor is.
With good fuel, no. Having been sitting over the winter months with a little bit of water mixed in, yes if its un plugged. Please enlighten me then, because as far as my understanding and experience goes with knock sensors, it's there to to detect detonation and adjust the timing due to an improper fuel to air mixture. Being that its located on the side of the block in a drainage port, chances are it may have gotten touched during the winterization/dewinterization process. And yes they do go bad as well, hence the lean code and hesitation. Which is why I threw that suggestion out there. It's real easy to check and mark off the list of possible problems. Being that its an older boat with pretty basic efi, they do tend to knock here and there when idling if you really listen for it.
Old    Chris Dirty (Dmac420sj)      Join Date: Mar 2012       04-17-2013, 7:30 PM Reply   
Word!^^^^
Old    Cory D (cadunkle)      Join Date: Jul 2009       04-18-2013, 7:29 AM Reply   
You could lock out your timing at 32* in these low compression marine engines and they wouldn't knock or ping at idle with no load. Flat out not gonna happen. Not even with 6 month old gas. Water in the fuel would not result in knock/ping/predetonation. It would result in poor running or stalling but will not cause detonation. If you're concerned with timing issues, check the initial timing and ensure it is advancing properly to where it should be.
Old    Detox (bass10after)      Join Date: Feb 2010       04-18-2013, 8:52 AM Reply   
thanks for all the help guys. don't get to into it with each other, this isn't an mb vs tige thread hahaha ... would a bad map sensor or tps sensor cause any of these symptoms too? i haven't had a chance to get the boat from storage a do much else to it except check some of the hoses as mentioned and noticed the map sensor was pretty lose so i tightened it down. My hope would be that it was causing a vacuum leak but since its my boat and not somebody else with better luck i'm sure it probably wont be that simple
Old    9Drozd            04-18-2013, 12:05 PM Reply   
You're right, if you put 32 degrees of total timing in it, it should not ping or detonate assuming you have a mechanical distributor advancing the timing as the RPMs increase with absolutely no computer interference. With the efi systems on the gm marine engines, the distributor is set at 6-10 degrees of initial timing and that's all the timing that the distributor will ever have. The ECM advances the other 22-26 degrees for the total timing. The knock sensor tells the ECM to retard or advance timing all across the RPM range based on it sensing pinging or knocking regardless if its audible to the human ear or not. So yes, at idle you may occasionally hear slight engine knock due to the ECM advancing the initial timing. This can also happen with 6 month old gas that has lost some of its octane and or with a bit of water mixed in. Regardless if the knock sensor is the underlying cause of the OP's issue, when called out, i'm going to justify myself.
Old     (HighVoltage)      Join Date: Aug 2010       04-18-2013, 1:32 PM Reply   
You can try running a higher octane fuel in there too.
Old     (WheelerWake)      Join Date: Mar 2013       04-18-2013, 5:15 PM Reply   
Quote:
Originally Posted by bass10after View Post
would a bad map sensor or tps sensor cause any of these symptoms too?
Yes to both of those...
Old    Cory D (cadunkle)      Join Date: Jul 2009       04-19-2013, 10:51 AM Reply   
Locked out timing at 32* mean 32* initial, and 32* at any RPM. Even like that this low compression marine engine will not detonate at idle with no load. If your numbers are correct and the ECM will try to get 36* timing at idle, it still would not detonate. There's no load and we're talking about a relatively low compression marine engine. Simply not gonna detonate at idle with no load.

Beyond that I highly doubt Indmar set up the timing table to shoot for 36* of timing at 700 RPM. This can be seen by letting the engine idle normally and putting a timing light on it. I'd bet dollars to donuts you're not gonna see more than 14*, and I doubt even that much. On most fuel injection systems ignition timing is set by RPM and manifold vacuum. i.e. As RPM increases the timing will be advanced. It will be advanced more if engine load is light (high vacuum) and less if engine load is high (low vacuum), or less in either case if detonation is detected.

Personally I won't own anything fuel injected. I need my stuff to be reliable, just plain work. It's probably some sensor, electronic component, or wiring. I don't know though, but I do know your engine will not detonate at idle with no load even with the ECM trying to advance the timing to whatever its limit is, regardless of if the gas is 6 months old.

Bottom line is that the OP's problem is not detonation related.
Old    Larry Engelbert (EngineNut)      Join Date: Nov 2010       04-21-2013, 6:58 AM Reply   
The LTR has a distributorless ignition ... the timing is not adjustable. That engine has two temp senders, one for the gauge on the dash and one for the ECM. It is possible that you could get the correct reading at the dashboard and the signal going to the ECM could be wrong. The one going to the ECM is used to adjust the fuel when the engine is cold. I would get the engine hooked up to a scan tool and see what temp the ECM thinks the engine is at.
Old    Eric (Fixable)      Join Date: Oct 2012       04-21-2013, 7:13 AM Reply   
Quote:
Originally Posted by EngineNut View Post
The LTR has a distributorless ignition ... the timing is not adjustable. That engine has two temp senders, one for the gauge on the dash and one for the ECM. It is possible that you could get the correct reading at the dashboard and the signal going to the ECM could be wrong. The one going to the ECM is used to adjust the fuel when the engine is cold. I would get the engine hooked up to a scan tool and see what temp the ECM thinks the engine is at.
This is exactly what I was thinking when I read the original post. I am not 100% familier with that engine in '99, but it most likely has an Intake Air Temp sensor as well. When those sensors go bad, they will usually read "full hot", or at the high end of their sensing range. This will make the ECU lean out the fuel mixture.

Your symptoms sound exactly like an engine that thinks its warm, when it is not. One of those sensors is dead or failing.
Old    Dave W (njskier)      Join Date: Jul 2005       04-21-2013, 6:41 PM Reply   
Just a few basic low cost things to start with.

Change the fuel filter if it is more than 2 years old (should be changed every 2 years)
Change your spark plugs. Look at the old ones to see if any looked fouled/wet/black with carbon. 90% of the time a rough idle/stalling problem is a bad plug. Run it again and see if the problem is gone.

Your engine has 4 coil packs that are sometimes a common problem. Look for carbon tracking between the posts on the coils (where the plug wires snap on) If you see any black lines connecting one post to another the coil pack needs to be replaced. Carbon tracking causes the spark to jump from one coil tower to another basically causing an engine miss.

My friend has an '01 MC with the same engine and his coil packs needed to be replaced. Hopefully yours are ok because they are not cheap. Good luck.

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