2012 Tohatsu MD50/35 jet rough idle

[kenaialweld]

I have a 2012 Tohatsu TLDI MD35 jet that I recently bought. Its has about 4 hrs run time on it right now. When I had it out yesterday I noticed while on idle it seemed to have a misfire or something, kinda like a quick hiccup. It ran fine at higher rpms and speeds, just did it on idle. Now as a disclaimer I am using 87 octane gas as I didnt realize they recommend 89 or higher. I will be using premium the next time out.

I did read a thread on here from a while back from someone that was having similar issues with their 50hp tohatsu, which is the same powerhead I have. I guess they replace the injector seals on it and all was good. Any thoughts? I did call the dealer and of course the generic answer was to just bring it in and they would reset the TPS sensor to start.

 

[pvanv]

Re: 2012 Tohatsu MD50/35 jet rough idle

You are under warranty. Use it. The dealer can run through the diagnostics to see what may be recorded at the ECU. Yes, cleaner fuel is better, but it should run OK on clean 87 octane. Many premium fuels are cleaner, so while higher octane in and of itself is not a requirement, keep in ming that most US 87 octane fuel is pretty poor.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

I will be bringing it in next week. Its a bummer though when we have such a short window to use a boat up here to have a brand new setup sitting in the shop. The darn ice just when out of most of the rivers and lakes just within the last couple of weeks.

 

[TOHATSU GURU]

Re: 2012 Tohatsu MD50/35 jet rough idle

What size battery are you using?

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

I will have to check when I get home. It was whatever the shop sold me as a package deal. I didnt check how many CCA it had, but it was just a standard looking 12v interstate battery.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

550 CCA 12v Interstate Marine/RV battery.

 

[TOHATSU GURU]

Re: 2012 Tohatsu MD50/35 jet rough idle

Your battery is too small. It does not have enough amps to energize the ignition system correctly. Shoot for 1000 CCA's and settle for anything over an 825 battery....Your dealer should not have let the engine leave with that small of a battery.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

Thanks for the advice, will be buying a new battery tonight and will try it out on monday. Out of curiosity though what would running a lower CCA battery cause for issues other than potential starting problems?

 

[TOHATSU GURU]

Re: 2012 Tohatsu MD50/35 jet rough idle

The engine's ignition system requires a minimum amount of CCA's to correctly start the the ignition sequence. A small battery will work the starter fine and will usually allow the engine to start, but since the system never gets the minimum juice it needs to work it just limps along. Your TPS will loose it's setting and your engine will run like crap. So, new battery and a TPS re-set and you should be fine.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

Well this is a tough one. It is not easy to find a marine battery with anything over 800 CCAs. Most of the shops here have large enough batteries, but they are huge (size wise) truck batteries. I think having such a huge battery in a little 17' jon with a 50hp is kinda nuts. I also dont like the idea of needing post adapters, just seems like an extra connection to go bad. I will do what I have to do though so the motor runs correctly. The battery shop guys didnt think I knew what I was talking about until I showed them the Tohatsu website where it shows the requirements. The owner appreciated me stumping him on this one, after 40 yrs in the business it doesnt happen to him much anymore.

 

[pvanv]

Re: 2012 Tohatsu MD50/35 jet rough idle

There should be a group-27 with 1000 MCA available in your area. That will probably be about 800-850 CCA, which should work OK, and should have the marine-style stud terminals.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

I did find one of those. It has 800 CCA/1000 MCA. I guess I can give that one a shot. It was considerably smaller than the group 31 that was the alternative.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

Well its off to the shop. I haven't had it in the water for a month, had a lot going on, but used it yesterday and it is still missing. It sounds a lot like the motor another poster here took a video of last year.

Will see how long this takes, summers are short here and the shops are busy.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

Well the guys looked at it and said there was nothing wrong. I have my doubts as my friends MD 50/35 of the same year purrs like a kitten. They told me they checked the compression, spark, checked for codes, and called Tohatsu to run it by them. They said the guy a Tohatsu said to run it at 900 rpms at idle instead of 700 rpms that it was set at when I brought it in. I guess I will just run it and hope for the best. I just dont like to be on glacial rivers with my family and be worrying that the motor is going to crap out, especially with only 7 hrs on it.

 

[pvanv]

Re: 2012 Tohatsu MD50/35 jet rough idle

Now that you have the new battery and the shop has reset the TPS, you may well be fine.

 

[Sea Rider]

Re: 2012 Tohatsu MD50/35 jet rough idle

+ Go for the higher octane fuel on your next outing, has better cleaning products, engine will run better.

Happy Boating

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

Whats interesting to me is that they told me the motor was still making the same sounds and little stutter. They told me some just do that because they run so lean. I find that explanation to be a bit bogus, as I have never owned a motor that sputtered when it was running right. Again, I will just have to run it and see how it does.

 

[kenaialweld]

Re: 2012 Tohatsu MD50/35 jet rough idle

And now to top it all off when I picked it up my gas tank was missing. After going back and forth with the shop manager that I did indeed purchase one when I bought the boat 3 months ago, and did have it in the boat, he gave me a new tank. He did say that they would eat the cost of the tank, but he couldnt do anything about the 5 gallons of premium gas that was in it. What a nightmare of a shop to deal with.