Bad TPS, transmission or mechanical transmission linkage?

**Ski-me** · 07-16-2013, 12:40 PM

Check your fluid level in your transmission. Just a shot anyways.

I've been going through similar things with my sister-in-law's Cobalt Inboard boat too. She has about 200 hours on it (1999) so pretty low use. I can idle in gear, and then hit the throttle....boat takes off then, slips out of gear, engine revs up and then clunk! Back into gear. Like it's missing or something. It did it periodically. I checked the fluid and it was halfway on the dipstick. Topped it off and didn't notice it.

A few days later, it did it again. I check the fluid and her records.....it appeared the transmission had never been serviced. I sucked it all out, added Mobil 1 Synthetic and it's all good now.

1+ quarts needed at $10 each, hand pump ($11). So, for $31 I changed the fluid and it's better now.

Just a thought anyways....

Now her engine won't start after being warm, resting and restarting. Just not reliable!

**djr47** · 07-17-2013, 09:51 AM

Thanks Jeff,

Will definitely by checking fluid levels in tranny this weekend.

Has anyone ever had issues with the throttle position sensor? I really think this is the issue based on what I've read on some other posts on here.

**djr47** · 07-24-2013, 05:10 PM

Fluid levels were fine in the transmission. Engine will run but will not go into gear. The engine will just rev in neutral if I gave it any gas in forward or reverse. Boat is with the dealer now, hopefully have it back by this weekend with a solution.

**djr47** · 07-30-2013, 09:17 AM

Got the boat back from the dealer last weekend. We had blown a couplet in the transmission some how. Boat runs now but of course as soon as we got it back from the dealer the boat started throwing check engine codes...

Very frustrating as the dealer took it out twice after they had fixed it and said everything was running perfectly. Haul it back 4 hours to our cottage and get a check engine code immediately after taking it out. I'm looking at buying my own code reader to figure out the problem.

**JimN** · 07-30-2013, 09:37 AM

Originally posted by djr47 View Post

First time posting on here but have used team talk extensively looking for quick fixes with great success! Thank you for the great advice on here from contributing users!

My family has a 2005 X-star (MCX 350) that has been a total lemon. Bought it used 5 years ago with low hours (120) and have not had a season where it didn't have an issue. Dealer is 4 hours away so it is quite frustrating especially with our short season in Ontario. Love the boat when it works but has been a total pain! Been to the the dealer once already this summer with a break down and we now have encountered another problem last weekend.

We have had a continual issue where sometimes when the boat is put into neutral we will get check engine. The boat will then not respond when put into gear in netural or reverse after check engine code is flashed. We usually then turn the boat on and off and the code will disappear and the boat will work fine. We asked the dealer to look at this earlier this summer when it was there for another break down issue which was fixed. Of course when they took the boat out for a test drive it would not flash check engine when put in neutral from gear so the problem was never solved.

Last weekend after getting a check engine in neutral I turned the boat off and on and started pulling a rider. Pulled for rider for about a minute followed by a fall. Pulled up again and the boat lost all power about 15 seconds into acceleration followed by the engine revving very high. The boat had obviously slipped out of gear. I put the engine in nuetral and it stayed running. Turned the boat off and on and tried to go into gear and the engine would just rev. Tried a few times on and off and putting in gear with no success. All gauges were fine, temp, pressure and volt.

I have been snooping around on here and feel like it is the TPS sensor. We were originally only having issues while in neutral shifting into foward or reverse but now the boat won't even go into gear at all. Has the sensor now completely failed? I will be trying to find the lever on the tranny to switch it into gear this weekend manually to rule out any transmission problems (I'm skeptical of this as it was just at the dealer and they checked the levels and they were fine).

If anyone could weigh in on this issue it would be much appreciated! I'm sick of having a dead boat! Just want to wakeboard!

Thanks

Codes aren't found by "feeling" anything- scan it.

Have you checked the impeller and oil cooler?

**JimN** · 07-30-2013, 09:40 AM

Originally posted by Ski-me View Post

Check your fluid level in your transmission. Just a shot anyways.

I've been going through similar things with my sister-in-law's Cobalt Inboard boat too. She has about 200 hours on it (1999) so pretty low use. I can idle in gear, and then hit the throttle....boat takes off then, slips out of gear, engine revs up and then clunk! Back into gear. Like it's missing or something. It did it periodically. I checked the fluid and it was halfway on the dipstick. Topped it off and didn't notice it.

A few days later, it did it again. I check the fluid and her records.....it appeared the transmission had never been serviced. I sucked it all out, added Mobil 1 Synthetic and it's all good now.

1+ quarts needed at $10 each, hand pump ($11). So, for $31 I changed the fluid and it's better now.

Just a thought anyways....

Now her engine won't start after being warm, resting and restarting. Just not reliable!

How long does it need to rest before not starting? Next time, open the throttle a bit and see if it starts- if it does, check the ECT for high resistance (more than about 1K Ohms). If you see high resistance, replace it. Whether it has the Mercruiser or Volvo-Penta, it works the same way as the Indmar.

**Ski-me** · 07-30-2013, 10:53 AM

Originally posted by JimN View Post

How long does it need to rest before not starting? Next time, open the throttle a bit and see if it starts- if it does, check the ECT for high resistance (more than about 1K Ohms). If you see high resistance, replace it. Whether it has the Mercruiser or Volvo-Penta, it works the same way as the Indmar.

Thanks Jim. The boat is in Idaho and I'm back in Colorado now. I'm hoping she will bring it into the MC or Cobalt dealer in the next week or so.

Rest time was anywhere from 30 min to 1 hour. I did try several methods.....give a little gas, give it no gas, give it a lot of gas.....still just didn't want to start all the way. It stumbled, runs rough, hear a backfire, and then stalls out. Lasts from 5-10 seconds before stalling again. Almost like a vapor lock, heat soak type of issue. If they find someting, I'll report back.

Thanks!

**JimN** · 07-30-2013, 02:55 PM

Originally posted by Ski-me View Post

Thanks Jim. The boat is in Idaho and I'm back in Colorado now. I'm hoping she will bring it into the MC or Cobalt dealer in the next week or so.

Rest time was anywhere from 30 min to 1 hour. I did try several methods.....give a little gas, give it no gas, give it a lot of gas.....still just didn't want to start all the way. It stumbled, runs rough, hear a backfire, and then stalls out. Lasts from 5-10 seconds before stalling again. Almost like a vapor lock, heat soak type of issue. If they find someting, I'll report back.

Thanks!

Have someone run it and let it recreate the problem. Once the problem presents, open the engine cover and see if it starts sooner than before. If the blower is used, heat soak isn't much of a problem.

**Ski-me** · 07-30-2013, 03:34 PM

Originally posted by JimN View Post

Have someone run it and let it recreate the problem. Once the problem presents, open the engine cover and see if it starts sooner than before. If the blower is used, heat soak isn't much of a problem.

Sorry about the treadjack djr.....

Jim, I've told her to video it on her phone when it happens again. Then at least a mechanic can actually hear what it's doing.

When it occured, I openned the engine cover to watch it continue to not start. All of these problems are still occuring while the engine cover is wide open.....blower also being used prior to starting as well.

**JimN** · 07-30-2013, 03:45 PM

Originally posted by Ski-me View Post

Sorry about the treadjack djr.....

Jim, I've told her to video it on her phone when it happens again. Then at least a mechanic can actually hear what it's doing.

When it occured, I openned the engine cover to watch it continue to not start. All of these problems are still occuring while the engine cover is wide open.....blower also being used prior to starting as well.

Carb, or EFI? If carb, it definitely could be vapor lock- can you verify that gas is going into the intake? With TBI, this is as easy as it it had a carb. If you see no gas being delivered, make sure the pump is activating when the key is turned to ON.

Has any work been done on the engine, other than oil changes and minor stuff like that?

**Ski-me** · 07-30-2013, 04:26 PM

Originally posted by JimN View Post

Carb, or EFI? If carb, it definitely could be vapor lock- can you verify that gas is going into the intake? With TBI, this is as easy as it it had a carb. If you see no gas being delivered, make sure the pump is activating when the key is turned to ON.

Has any work been done on the engine, other than oil changes and minor stuff like that?

It's a EFI, Mercury Scorpion 330HP engine. I think that's sequential injection, not TBI if I recall.

I'll check with her on the fuel pump turning on with key before start-up.

Nothing major on engine other than a few minor tune-up parts (plug, cap, rotor, fuel filter). However he did install a new alternator and possibly a new grounding wire......however, it was still behaving this way prior to his repairs.

**JimN** · 07-30-2013, 04:38 PM

Originally posted by Ski-me View Post

It's a EFI, Mercury Scorpion 330HP engine. I think that's sequential injection, not TBI if I recall.

I'll check with her on the fuel pump turning on with key before start-up.

Nothing major on engine other than a few minor tune-up parts (plug, cap, rotor, fuel filter). However he did install a new alternator and possibly a new grounding wire......however, it was still behaving this way prior to his repairs.

Someone needs to verify fuel pressure and quality, as well as spark, when it won't start. I have seen ground wires that were loose/broken and when the engine compartment temperature was high, the wires relaxed, breaking contact with the block and when it cooled, it was fine. Could be a connector that's doing the same thing.

**Ski-me** · 07-30-2013, 04:43 PM

Thanks Jim for the help. I just wish the boat was in front of me to get this thing resolved. I helped her pick the boat out so I feel slightly responsible that it's not performing 100%.

**JimN** · 07-30-2013, 07:22 PM

Originally posted by Ski-me View Post

Thanks Jim for the help. I just wish the boat was in front of me to get this thing resolved. I helped her pick the boat out so I feel slightly responsible that it's not performing 100%.

I don't know why you would feel responsible for the problems- Cobalt is a very good boat although I'm not as familiar with Mercruiser as I was.

You could call the Mercruiser tech support department, too- they'll want the engine and transmission serial numbers (inboard, right?), or engine, gimbal, outdrive serial numbers if it's a stern drive.

Bad TPS, transmission or mechanical transmission linkage?

Bad TPS, transmission or mechanical transmission linkage?

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