Tohatsu 40hp question......

[james082273]

I have a 2004 model 3-cyl 40hp tiller that I bought new off of an internet site in Louisiana almost 2 years ago. It has a couple of annoying problems that are probably related.<br /><br />The first is the idle. Out of gear it is as smooth as glass, in gear with a little load on the prop it is very good as well. Once the boat starts moving though and there is very little resistance I start to get this very annoying "chattering" sound and the engine shakes pretty noticably. It's has done this since new. I wouldn't care it's just that 90% of my fishing is trolling .<br /><br />The other problem is this thing seems to eat spark plugs. I'll be cruising along and it will start to missing and poping. Change the plugs and its fine for another few days or so. The plugs that I take out actually always look okay, not fouled at all. Very strange.<br /><br />I have always run fresh fuel and good oil. I even checked the resistance through the power packs and they are consistent.<br /><br />I'm thinking a high float level or maybe something weak in the ignition other then that I'm clueless.<br /><br />Any ideas? Thanks in advance!

 

[TOHATSU GURU]

Re: Tohatsu 40hp question......

It could be almost anything, but it is probably a carb setting or dirty carbs.

 

[james082273]

Re: Tohatsu 40hp question......

Okay thanks. I actually posted this a little over a year ago hoping someone had any fresh ideas or experiences. <br /><br />I guess I just got a fluke. What gets me is what ever is wrong with it was straight from the factory. I hope it's a sync or float level problem. I'll tear into the carbs this winter and see if that helps.

 

[nevd]

Re: Tohatsu 40hp question......

One easy check to make is to measure the dimensions between the throttle shafts and the pivots on the vertical link which controls the opening of all the carburettors. If these dimensions are not equal (say to better than .5 mm), carburettors which are synchronised at one throttle opening will not be synchronised at another opening. Clearance on the carburettor mounting holes is probably enough to solve any problems.<br /><br />This has been a problem on some 3 cylinder Tohatsu motors and in some cases the errors mean the vertical link must be twisted to decrease its lenght between two carburettors.

 

[james082273]

Re: Tohatsu 40hp question......

Thank you! I'll check that out first.

 

[TOHATSU GURU]

Re: Tohatsu 40hp question......

With a two year warranty on the engine it might have been a good idea to take it by a dealer. Also, there is no record of that linkage ever being incorrect from the factory...At least, no dealer has filed a warranty claim or reported a case of it. I'm not saying that it could not happen, but there's just not a record of it on a new engine.

 

[james082273]

Re: Tohatsu 40hp question......

I should still have some time left, I'll have it 2 years in December. <br /><br />Since I bought it online I didn't want to mess with a local dealer since I didn't think it was all that serious but I think I'm coming around.

 

[TOHATSU GURU]

Re: Tohatsu 40hp question......

Always take advantage of the warranty. It dosen't matter where the engine was purchased. I assume you purchased it from Houma, but your local dealer gets paid by Tohatsu for warranty work...paid well. They should welcome the chance to earn your business for the future.

 

[Me and my 90A]

Re: Tohatsu 40hp question......

Jon, that chattering, almost like a hourse voice is due to synchronization. I had the same thing with my 90 for years. I recently took the carbs and they were clean as a whistle. Taking them off and cleaning didn't help, but what did help was studying the low speed (idle) system design on them and realizing how important the synchronization is. First thing I learned was that the when adjusting the carb links, you need to visually make sure that the carb "butterflies" are completely in sync with each other. Their position when closed effects the 'pilot air jet' (tiny holes for air intake into the pilot system) and once opened a degree or two, they completely reroute the air flow into the pilot system. If not completely identicle, then they are not in sync. Once this is done, the next step is to adjust the pilot screws. The book explains the procedure, but I didn't get the desired effect until I went almost a 1/2 turn past the book specs, so, I would not use the specs as a difinative but only a reference. If adjusting the pilot screws, be very careful not to over-tighten them when seating as they will mash and may damage the seats.