Problem starting boat about 60% of attempts

[littlejrs]

I have a Mercruiser 5.0L MPI Bravo engine and recently I have had problems starting my boat. The first time I had an issue, I couldn't get it to start at all and gave up as to not drain battery. I took in to the mechanic and they stated it started right up for them. I asked them to check the connections, ground, batteries and they found nothing and the problem I had did not happen for them. I picked it up and took it for a weekend trip. The first two times I started it, it fairly quickly. Then after driving it for 2 hours and then letting it sit for 1-2 hrs, I had a problem starting it. I had to push the button on the throttle and push it forward (wasn't sure the proper terminology) and it started right up. I have noticed that when going at slow speeds, it doesn't seem to run as smooth as it used to but so slightly it wouldn't be noticeable to anyone else. I was told on the trip that it was the IAC. Replaced it but problem still happening, but not every time I try to start it. So I again took it into dealer mechanic and again they state it started right up for them.

On a side note as I am not sure if it's related. I used to keep the gas tank full and put Sentry fuel treatment in it. More recently it has not been completely full and I hadn't put the fuel treatment in it in the last 1-2 yrs (so bad with time frames). The tank is now down to 16 gallons as I was trying to empty the old gas before filling with new gas and I went ahead and added fuel treatment to the remaining gas.

I am at a loss.... Believe it in either the fuel or the ignition system. Anyone have any experience with this or best recommendations of how to narrow it down?

 

[mr 88]

First off you should be giving it some gas when you start it, so by engaging the "button" and pushing the throttle forward a couple times and then hitting the key is normal.Other than that the only thing that comes to mind is to rebuild your carb as the idle circuits may be clogging up.

 

[JustJason]

First off you should be giving it some gas when you start it, so by engaging the "button" and pushing the throttle forward a couple times and then hitting the key is normal.Other than that the only thing that comes to mind is to rebuild your carb as the idle circuits may be clogging up.

I have a Mercruiser 5.0L MPI

Hmmmmm.........

 

[mr 88]

Sorry didn't see the MPI.I do wonder why though that when he does give it gas it fires up.

 

[Bondo]

On a side note as I am not sure if it's related. I used to keep the gas tank full and put Sentry fuel treatment in it. More recently it has not been completely full and I hadn't put the fuel treatment in it in the last 1-2 yrs (so bad with time frames). The tank is now down to 16 gallons as I was trying to empty the old gas before filling with new gas and I went ahead and added fuel treatment to the remaining gas.

Ayuh,..... Welcome Aboard,....... Start with the basics, pull the fuel Filter, 'n inspect the Contents of it for water, 'n crud,.....

Replace with a new one, 'n Try it,....

 

[littlejrs]

Yes mine is MPI and have never had to give it gas to start in 9yrs. Dealer said that's bad to do on my engine.

I did have the dealer replace fuel filter and screen (out of convenience) and will pick up tomorrow and take it for a ride. Also I plan to add some ethanol free gas. Crossing my fingers.

Any chance those symptoms could be a bad cap and/or rotor? I have never replaced them. Probably should and will as regular maintenance. Just curious of that could be the problem.

 

[Fun Times]

Yes mine is MPI and have never had to give it gas to start in 9yrs. Dealer said that's bad to do on my engine.

I did have the dealer replace fuel filter and screen (out of convenience) and will pick up tomorrow and take it for a ride. Also I plan to add some ethanol free gas. Crossing my fingers.

Any chance those symptoms could be a bad cap and/or rotor? I have never replaced them. Probably should and will as regular maintenance. Just curious of that could be the problem.

Yep it's time for a full tune up even if it's not the main problem.

What year is the engine?

You'll want to try cleaning the throttle body and replace the IAC muffler should your engine model have one. http://forums.iboats.com/forum/engin...something-else

 

[JoLin]

Bondo and Fun Times are giving you the right advice. A good tune-up might very well fix it. A cap and rotor that are 9 years old are long overdue for replacement. How about the spark plugs? Are they that old, too? If they are, toss them.

 

[littlejrs]

Thanks guys! I already replaced the IAC muffler and ordered a new cap and rotor. The sparks plugs are maybe 2 yrs old and haven't used boat but maybe 25 hrs in that time. I'll replace the cap and rotor since it's overdue anyway and I'll see where I am after that.

 

[tkarvelis]

I would do the wires too. I have a 95 5.0 LX with carbs and you issues are like mine. Test rode the boat, bought it, started in the driveway with muffs, took it to the lake and could not get it to start. Towed it over the the marina, and he started it in 5 seconds, towed back to launch would not start. I got it to start, and ran it for the day. Fought with it a second weekend, and was ready to pull the transom drain while on the lake LOL. I took it home and replaced wires, cap, rotor, and carb fuel filter. It is a whole new boat. Cap, rotor and wires were 20 years old. Runs great now. Check or change the wires. Mine were under $50 for them.

 

[littlejrs]

No Title

Ok so I replaced the cap and rotor and no difference.

I now have some more information to help diagnose the problem though. It seems now the throttle doesn't seem to be functioning normally. Let me see if I can explain it correctly... Before, when I would put it in forward gear, I would hear it 'pop' so to speak into gear. Now it is not doing that anymore in forward. It only 'pop' into gear when putting into reverse. Also, I have noticed I have to give it more throttle once in forward to get the boat moving. (I recently opened the engine hatch when doing this and noticed that the throttle cable isn't moving very much when first giving it throttle after placing into forward. Note: this does NOT happen in reverse. Actually, the boat is quite responsive in reverse and the throttle cable moves immediately when giving more throttle after placing into reverse). I am guessing this is related to my issue with the boat not starting when in neutral since it appears it is not getting enough gas. When I push the button on the throttle and give it more gas, the boat always starts. So here are my questions....

1) Is there a way to check if the throttle cable is adjusted properly and/or needs to be replaced?
2) How do I check to see if upper & lower shift cables are properly adjusted and/or needs to be replaced?
3) Is there anything else that would affect how much gas the engine is getting when in neutral?
4) I read that the one cable should be 6inches from center of hole to center of adjust piece. Mine is 7+" (see picture). Is this incorrect? Am I incorrect?
5) Do the upper & lower shift cables affect how the throttle cable functions?

That's a lot of info to ask about for now.

 

[NHGuy]

You don't normally need to adjust the throttle cable. But some lube on the engine end could help. When putting the boat in gear you move the lever "smartly" into forward til it engages. Then while the motor is still idling but now in gear, you can add throttle.
Seems like this is secondary to your main running issue though. Start with the basics, plugs, cap. rotor, wires.

 

[littlejrs]

Yes I know how to put it into gear and give it throttle. What I'm saying is that it's not responding the same now as it had been the last 9yrs I've had the boat. I could feel it shift into gear (like a popping) and was very responsive when giving more throttle to go. It's not as responsive in forward and I can't feel it shift into gear like I used to. I can still feel it and is very responsive in reverse.

Plugs, cap, rotor and wires replaced and that is NOT the issue.

 

[NHGuy]

cool,didn't see the wires. I don't know MPI, so will just observe.

 

[littlejrs]

Bump

 

[Bondo]

Ayuh,..... With a Helper,... Remove the throttle cable from the throttle body lever,.....

Advance the throttle on the controller to Wot, 'n observe/ measure it's travel,....
Measure the travel needed by the throttle body to go from idle to Wot,...
Do they match,..??

Try pullin' on the cable end, ' see if it's sloppy or loose,....

If the cable checks out,... I'm guessin' it might be a problem in the controller itself,.....

An Mpi, should start quickly in neutral, at idle, All by itself,.....

Did ya inspect the Contents of the fuel filter,..??

 

[littlejrs]

My boat does not start quick in neutral when in the water. It starts fine hooked to the muffs and hose.

 

[littlejrs]

Oops I forgot to add that Yes the fuel filter was replaced but difference in starting or performance.

 

[littlejrs]

Oh btw, it turns out water was in one of my spark plug areas from a crack in the cylinder head.

 

[nateo]

No Title

The man down under (Chris) has a good video on youtube for adjusting shift cables. Here's another doc for the more difficult one.

http://www.thehulltruth.com/boating-forum/593963-how-adjust-upper-shift-cable.html