Throttle issue with my Tohatsu M60B

[jstaz]

I took my boat for the maiden voyage and started having throttle issues. We went WOT from the landing to the mouth of the bay so about 15 mins. All of a sudden the RPMs sky rocketed and I throttled down. Then while trying to idle it died. I figured it was ventilation. Sound correct?

I then had a little trouble getting it started again. I finally did and we were under way under WOT again. Same thing happened.

We turned around to get home but as we went I noticed that I was not able to get all the power out of my engine as before. Originally we were cruising at about 5400 RPM hitting 30 MPH or so. As we went I noticed that we couldn't go over 3400 RPM or the engine would quit. The RPMs would slowly start decreasing RPM without me touching the throttle. by the time we got to the landing again I tried to get WOT but even with my throttle full open I could only get 3200 RPM. I took the cowling off and everything looks tight and good to go other than the drain screw on the carb is leaking. Would that have something to do with my trouble?

I got the boat home and flushed the engine and it will idle and get in gear forward and reverse. Unlike while in the water, where I had to quickly lower the throttle lever on the top of the throttle case and push the throttle forward to get in gear and keep the engine running.

Please help with terminology and my problem. Thank you in advance.

Joe

 

[pvanv]

Re: Throttle issue with my Tohatsu M60B

Joe,

Check your owner's manual, page 72. That explains the safety warning systems. Your motor has 2 RPM-limiting features; one for over-RPM (such as ventilation or wrong/bad prop) and another for overheat.

You may have over-revved, which then limits the RPM. That could be due to a bad rubber hub in the prop, or if the prop pulled out of the water and ventilated. The engine will typically run rough if hitting the RPM limit, since the spark gets staggered to prevent over speeding. That will also give you wet plugs, which can make restarting a little difficult.

Also, the motor may be detecting an overheat. When it sees overheat, it limits to about 3500 RPM, +/- 400 RPM, until the condition clears. It should also turn on the buzzer. Is there a good stream of water from the telltale port? If not, check to be sure the telltale is clear of any obstructions or salt buildup. You can do that while the motor is running, by pushing a stiff wire into the check port to free any debris, which will then be pushed out by the water stream. If you still don't have cooling water flow, or if it has been a couple of years since the water pump was serviced, it's a good idea to install a water pump kit. I would recommend a complete kit with the cup and wear plate, instead of just the impeller. Part # 3F3652311M List Price (MSRP): $92.18, available at any dealer, including me.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

I have a really good stream of water coming from the pump. However, the symptoms of the overheating sounds to fit the bill. What else can I do to find out more about this problem? The guy I bought the boat from said he had the water pump replaced this year. Could there be something else that I could replace or look at?

For the rubber hub can I just take off the prop and tell if the hub is bad or do I need to bring in the motor to a mechanic?

Thank you very much for your help. I am new at all this and I thank you for helping me learn more.

 

[TOHATSU GURU]

Re: Throttle issue with my Tohatsu M60B

Pumps being good or bad can be just a matter of degree. It might be pumping just a little less than called for. To check a hub just remove the outer hardware, make a mark with a permanent marker across the prop assembly, put the hardware back on and run the crap out of the engine. When you come back check and see if the mark has separated. No separation means its fine.

 

[pvanv]

Re: Throttle issue with my Tohatsu M60B

I have a really good stream of water coming from the pump. However, the symptoms of the overheating sounds to fit the bill. What else can I do to find out more about this problem? The guy I bought the boat from said he had the water pump replaced this year. Could there be something else that I could replace or look at?

Does the buzzer sound? If so, you are definitely getting an overheat detection.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

No buzzers were going off at all. I was told by some guys I work with that I may have water in my fuel lines. Does that sound plausable? Could that create the same symptoms I am having?

GURU... Thank you for the hub info. I'll try that tomorrow.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

If I had lost a cylinder and only been running on 2 would that cause my throttle to be full open but only run around 3000 RPM?

If so, How could I fix that? Would that also have given me the symptoms I have?

Thank you in advance for all your help fellas.

 

[TOHATSU GURU]

Re: Throttle issue with my Tohatsu M60B

That would be a dead cylinder and the engine would not develop full RPM...That could be from a lack of compression or lack of spark or lack of fuel on that cylinder. You would fix it by taking the engine into a mechanic that knows how to rebuild an engine.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

Thank you for your help. I changed the spark plugs and hope that will fix the problem. I am having a mechanic look at it now so I hope it would cost much.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

well i brought my motor into the shop to get it looked at. The mechanic that looked at it said that all three cards were really gummed up and had a lot of calcium build up. So the parts that he needs to buy to fix this is a crab kit for each carb he told me. $189 for parts, and $360 for labor so total $641 was what I was quoted. The math didn't add up.

He believes that may be the reason my motor ran the way it did.

Questions... Does that sound correct? Is this all a good price for the south Alabama area? Is it difficult to do myself with little to no knowledge about carbs? Does he know what he is talking about? I hate to second guess him because I know he has been doing this for a while. However, I don't know much about these things yet and I am not familiar with this mechanic yet and his knowledge/motives. Is he trying to suck me in for spending more money?

Your help is needed and appreciated.

 

[TOHATSU GURU]

Re: Throttle issue with my Tohatsu M60B

Possible...Labor might be a hair high though or maybe he is including a little extra A & T time. Did they do tests for fire and compression?

 

[pvanv]

Re: Throttle issue with my Tohatsu M60B

Assuming he will be charging for 4 hours at $90 an hour, that sounds OK, if he is figuring in time for testing both before and after repairs. Shop labor rates vary from below $75 to over $100 an hour.

As Elvin suggested, confirm that they did in fact test/diagnose ignition and compression as well.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

This guy did not test anything. All he did (that he told me) was take the carbs off and look at them. He has done nothing further. I told him to hold off on any repairs. I have since done more calling around and found a Tohatsu dealer that will do labor for less and stated that they may not even need a kit but just to clean the carbs real good. They stated labor estimate is an hour per carb. Should I have them do an ignition test/diagnostic before and after? I just replaced the spark plugs and it has not been run since that so I know they will work.

What is A & T time?

The ignition and compression was done when I first got it and they stated everything was great. Compression was 120 and the third was 125 or 130? i can't remember the exact number. It is in the paperwork though.

This check was completed by a different mechanic than who currently has my boat. The reason is because the place that did the check in the beginning does not work on Tohatsu motors.

 

[pvanv]

Re: Throttle issue with my Tohatsu M60B

In our shop, we always start with diagnostics before starting repairs, unless the problem is something super-obvious. Otherwise, what criteria would they use for doing a repair? Sometimes a carb kit is not needed -- depends on how bad the rubber bits are. The kit for this motor does all 3 carbs, so is a bit pricey... but if one needs a kit, it's likely that the other 2 do as well.

A & T time is Analysis/Adjusting and Testing time.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

Well the carbs were cleaned and put back together. took the boat out and had the same issues.

Fired up and idled well. Ran at 3200 RPM great. Soon as I tried to go WOT I hit 5200 RPM at after about 30 seconds the power would cut back and die. I woulf fire it up again. the same thing happened. After that the engine would not get over 3200 RPM. I called a tech. and was told to try to hit the choke when the power started to die down. I did that and it killed the motor when i held it down for a few seconds. It would die down but come back up to speed if I just tapped the choke. The primer bulb stayed hard the entire time. The gas tank vent was open. The motor is firing on all cylinders. The tech. states he doesnt think it is fuel related. He believes it may be a wire harness issue like maybe it is not grounded well enough. It sounds completely fuel system related to me but like y'all know I am new at all this and don't know much. What do you think? Any help?

The manual states 4900-5600 RPM is operating WOT.

 

[jstaz]

Re: Throttle issue with my Tohatsu M60B

Just an update...
I have taken the motor into a mechanic who is Tohastu certified and they have told me this...

The oil injection had stopped working and no oil was being mixed in. Because of that now I have been quoted $1500 in repairs. All 3 pistons need to be replaced, all 3 cylinders need to be honed, and 2-3 barrings need to be replaced. I have been advised that due to the age and model that depending on what else may break down through time it could cost a lot more money or you may not be able to find parts for it. i.e. the crankcase. I have little money so I am trying to be smart about things. Should I replace the motor with a newer one or fix the one I have and risk not finding parts in the future for repairs?

I am weighing all options. I have found a 2002 90 HP Mercury that will fit on my boat. He is asking $2275 including controls. He will take my Tohatsu for parts but will only give me $200 for it. I am thinking I may be able to sell him my 9.9HP Evinrude too to help off set the cost.

Advice anyone? Any would be helpful.

Anyone looking for a 1994 Tohatsu 60 HP M60B for parts or fix it and use it?

 

[pvanv]

Re: Throttle issue with my Tohatsu M60B

That's a VERY reliable oiling system. What failed? Are you sure of the diagnosis? If it did fail, lack of oil should not have caused your original symptom of over-revving.

However, mixing in the wrong oil, and having it gel and stop up the oiling system could have caused reduced oiling, ending up with scrubbed pistons, which would indeed slow down the motor as it was self-destructing the pistons.

I would double and triple check everything to find the root cause of the issue before doing any repairs on a possibly 18 year-old motor. The crank bearings are not individually replaceable (though the wrist pin bearings are), so if they are bad, you need another crank assembly, which probably makes that motor uneconomical to repair.

 

[jcjcat]

Re: Throttle issue with my Tohatsu M60B

I would say that the mechanics didn't do the right operations !
If i were in charge, I would :
- first start a run, and while the motor seems ok, stop it and remove the spark plugs. Are they identical, or is one fouled ?
- same as above, but WOT, and same tests and questions
then
1 - remove and check the spark plugs, identical ? color ? traces of broken parts having moved into the compression chambers ?
2 - check the compressions - you can do it yourself, with a rope around the flywheel, you can easily sense if they are more or less identical ! If one is evidently loose, there is a groove in the cylinder bore, or a broken piston
3 - abnormal noise when the motor is running ?
4 - air bubble(s) into the oil pump transparent hose - this means that the oil could have been interrupted if the oil filter were opened - then add 5% of oil into the gasoline and go for a run test
5 - if the same symptoms were still present on the sea, immediately check the secondary side resistance of the 3 ignition coils, with an ohmeter - preferably after having removed the ignition wire from the coil. There could be an internal open circuit inside appearing after a while, the internal secondary wire is very thin, like a hair, and if it breaks, there is an electrical arc inside the coil ...
6 - replace the CDI ignition unit - could become defective when hot

Good luck !

 

[pvanv]

Re: Throttle issue with my Tohatsu M60B

I assume you had a reason for replying to a year-old post?

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