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Tohatsu 2008 90 TLDI Strange Problem

S

skip_mff

Member
"Hi,

running a 2008 brand new Tohatsu 90 TLDI on an 18foot open boat and being coming across something weird. When running at relatively low revs, say 1400-2200 for various trolling speeds after say 15 minutes at randomly the engine appears to choke for a second or two and then resume normally. The best way to describe is would be the opposite to a surge, almost like the choke flicked on.

At cruise and flat out runs fine with no such issues. Fuel tank is vented, running to a Racor and then through an inline Lowrance fuel flow meter, but don't think either of those are causing the problem.

Boat is currently over-propped and running just shy of 5200rpm, so have a 13P on the way to replace the factory 15P, not sure if this is a contributing factor or not.

Due for the 10 hr service shortly, but wondering if anyone knows what this might be.

Skip"
 
"Nick, the Guru will probably

"Nick, the Guru will probably drop in with a suggestion but if you would, post the results of your service visit.

I'm quite interested. Considering a pair of these for a dual engine set-up but still gathering whatever first hand info I can on these. Have never seen one outside of the showroom and the closest dealer is over an hour from me - so interested in the findings and your overall opinion...."
 
"Hi Graham,

Not too optimis

"Hi Graham,

Not too optimistic on the service results as I'm based in Malta and been told that the only dealer here doesn't have the diagnostic computer! Will check out first hand if that's true or not.

So far I can comment as follows:

Starts great without issues, was impressed in fact. Very quiet at idle, though I noticed the engine does vibrate a bit two stroke style, I don't think it's anything to be worried about, it seems to rock on what feels like rubber. With the engine off if I wiggle the engine a bit, it feels like rubber dampers or something. Not sure if they can/should be tightened or if this is normal.

Barely any smoke out the back, in fact ppl think it's a four stroke. Adjustable Trolling function isn't working for me, though the loom seems all connected up but will get that checked.

Confirmed on another forum that this happens as well to someone running a 2003 90TLDI, he describes it as a falter for a split second at lower revs, which is what I have. But says engine has run flawlessly and not let him down for 6 years, and he has no fault codes on the diagnostic.

If you pop the cover, lots of plumbing of the various oil and air feeds, it's quite busy inside there, and the back center has air and oil bleeds if I remember correctly.

Have come from twin Merc 5.7L EFI V8's and not run outboards for years, last was a Johnson 50hp 2 stroke 15 years ago, can't really compare to others.

Doesn't appear to use much oil and I believe for the first 7 hrs its set to use more, so that's good as well.

Economy wise, all up weight with ppl is 1220kgs (The dry weight of the boat is 550kgs, main engine 143kgs, Auxillary 37kgs, 90kgs fuel, 40kgs water, around another 60kgs of additional weight from other fixed items; approx all up weight of 920kgs excluding people on board which would typical be around another 300kgs.)

Top speed GPS is around 29 knots trimmed up and at 5150 (32 litres per hour), cruise at 3900-4000, 19.5- 20.5 knots using 14.6 - 15.5 litres per hour with current prop set up. Used to use 50 litres per hour at 20 knots with previous boat!

Nick"
 
"The TLDI series don't req

"The TLDI series don't require a diagnostic computer. This system has a built in diagnostic mode. Through a combination of the 3 lights and the tach reading, the dealer can retrieve all necessary trouble codes without a computer. That's one of the beautiful things about these TLDI's from a service standpoint. Even the consumer can put it into diagnotics mode although you'd have to have a service manual to interpret what the lights/tach readings mean."
 
"Could be as simple as a spark

"Could be as simple as a spark plug...Could be anything. Most likely thing is a voltage loss due to extended battery cables,too small of a battery or the TPS sensor isn't set correctly."
 
"Hi Guru,

Thanks for your a

"Hi Guru,

Thanks for your advice and suggestions on what to check out. Will check the condition of the plugs on its first service, but it runs fine flat out and at cruise etc.

I don't think its the batteries as they are brand new and have 2 x 110amp batts, when I'm running the selector is set on both to charge.

However the batts are located in the center console and are extended although total length isn't more than 3.5-4m maximum but there is a join. What would be the best way to monitor/check this? My GPS head unit can display voltage but not sure if that's useful?

About the TPS sensor, is the a procedure to follow to check/set/reset it?

Thanks"
 
Its the CCA of the batteries a

Its the CCA of the batteries and the voltage loss to the engine that is probably causing your problem. Back to the dealer to determine if it actually is the problem...And they need to check the TPS. The very last thing you need to be involved in is the repair of your new outboard. It has a warranty. Utilize it and avoid the stress.
 
"I will bring up those two poi

"I will bring up those two points with the dealer and hope for the best as we don't get a very professional service here but will reserve final judgement to after the visit.

The CCA of the batteries is within Tohatsu spec for the 90TLDI so based on your feedback I would have to say voltage loss over the extended cables. Is there a recommended procedure for extending cables, as the gauge looks good, so only conclusion is that it's the join.

The GPS head unit does show voltage fluctuating at times from 12.9 volts to 14.1 volts but I don't get this power loss during the fluctuation.

I will also ask him to check the TPS sensor I only hope they know what they are looking for! Malta is a small island with limited resources!!"
 
"The Tohatsu spec is correct,

"The Tohatsu spec is correct, but it does not really allow for any variance off of the rest of the system in terms of degradation. IE Voltage loss due to cable length, resistance build up in the cables or at the joining point(always pay the difference for longer cables rather than joining them). Even the batteries may be off of spec due to age or default. If the fault is in the battery system it is probable that each aspect of it in total is the culprit rather than on specific part of the system.

The TPS is easily re-set and you could do it yourself, but I would really prefer that they re-set it, at least once, themselves. They might need the practice and at least it will reinforce the idea to them to do it correctly."
 
"Thanks, will see maybe this w

"Thanks, will see maybe this winter if I can remove the factory short cables and run longer cables straight from the engine as per your advice as don't think the dealer will do this.

Everything is brand new so don't think there is degredation etc.

Curious to know a bit more about the function of the TPS sensor in terms of how this might be affecting me and what it does. Is there somewhere I can read up perhaps?"
 
TPS is the trottle position se

TPS is the trottle position sensor. It controls the butterfly valve and advancer arm. If it is set wrong it screws with the ECU and causes the engine to malfunction at different RPM's.
 
"Mechanic came round today to

"Mechanic came round today to do the first 10 hr service. Spoke to him about the issues. After changing the lower gear case oil, moved up to the plugs and found they were pretty fouled. Dont suppose trolling (fishing) for extended periods of time at lower rpm's is a good idea during the break in period.

Will see how it runs with the new plugs. Found that the button used to query the ECU on the key and also to set the trolling rpm wasnt working. The part of the look that powers the key had the plastic retaining clip broken and was taped instead! Mechanic reckons it may have been playing around that could be causing the voltage drops and seems to have damaged the switch/button on the key.

He even tried a spare ECU just in case but that wasn't the issue and the ECU wasn't 'talking' to him via the rpm guage when queried.

They will be ordering a replacement grey connector and a new key barrel/switch.

He checked the TPS and reset it and said it was working fine."
 
After it's first service i

After it's first service it the problems I had continued as the parts hadn't arrived and then I pulled the boat out mid September.

Shockingly I haven't gotten around to sorting it out but I'm certainly going to have a good look at the battery Cold Cranking Amps and also as TG suggested the extended cables.

Would you advise removing the extended cables and just run a single longer set directly from the engine up to the batteries?
 
"As an update to this the deal

"As an update to this the dealer came over with a replacement key switch, however after testing various parts of the loom, he found the key switch to be functioning but a problem down near the engine.

He eventually found that the main harness plug that comes from the control box/guages and connection to the male socket as part of the loom on the engine had a problem. For some reason the out of the 7 or 8 female pins on this plug, 4 of them were pushed down/recessed therefore not making contact.

The dealer replaced the entire loom including the separate one with the broken grey clip. The trolling function/keyswitch now works including communication with the ECU. No fault codes were stored, however he reset the TPS sensor as good measure.

We also replaced the wing nuts on the batteries that the installer had used with locknuts, as he pointed out that wing nuts have a habit of coming loose.

When the weather breaks will take her out for some sea trials and see if the problem has gone away.

Would be interested to hear TG's views on the issue, whether if these pins weren't making complete contact it could have caused problems.

After that I will look at the fuel system as I do have an inline fuel flow sensor (Lowrance EP-65) as the only external element."
 
"No contact or more likely, in

"No contact or more likely, intermittent contact would certainly be a likely problem. It sounds like the original installer forced the connectors together jamming some of them down to far. It's not a common problem on Tohatsu models, but I have seen the same problem on some Suzuki harness's from the late 90's."
 
"Update:

I stil have my str

"Update:

I stil have my strange intermittent missing problem at 1400-2000rpm, and as it's now been quite some time I've asked the dealer to get on to Tohatsu for advice.

As it's not something that happens all the time it's hard to replicate on the spot....aside from the battery extension issue that TG mentioned, I wonder if I have a slightly faulty injector or something similar.

This weekend for the first time the engine missed for 1-2 seconds at high rpm 4,400 which hasn't happened before.

Work carried out so far in relation to this issue
TPS sensor reset several times
ECU queried for fault codes, no faults logged
Main engine harnesses from console to engine replaced
Visual Inspection carried out by dealer at the console (connections) and engine side.

I'm not sure if one of the many sensors on the engine could have an intermittent fault or as I mentioned an injector. But will keep this post updated.

TG, fancy a holiday to Malta, Europe?!!"
 
"I don't think your tiny i

"I don't think your tiny island could support the weight of my over inflated ego


I'll ask around and see if anyone else has had one of these show up. One out of a hundred of the early A models would sometimes get a voltage spike from the rectifier. But, I have never heard of a B model that did it as part of a normal running condition."
 
"Thanks TG, it's a strange

"Thanks TG, it's a strange problem indeed!

Should I be stressing more about the battery extension issue and perhaps insist that they run one length from the engine to the bus bar in the console? You were focusing alot on this and it still hasn't been addressed by the dealer as he didn't seem to think it was an issue with the boat still being only 12 months old."
 
"I would be worried long term

"I would be worried long term about the cables, but as you are not getting any malfunction codes that's less of a "worry now" deal. Tohatsu thinks you may indeed have an issue related to the propeller. They would like you to run a 12 or 11 pitch, instead of the 13 and see if that cures it. Theory is that the engine is periodically loading up and just happens to burp ,at that RPM, until it clears it out."
 
"Hi TG, when I tried a Solas A

"Hi TG, when I tried a Solas Amita 3 - 13.75x13P I was hitting the limiter even with full fuel and 3-4 people on board.

Last summer I ran for 2 months with a Solas Alcup 4 blader 13.25x13P and it did burped with that, but the performance numbers weren't that great. (but I didn't hit the limiter unless on my own)

As I had sold my factory 15P, I tested the Amita 13P, and whilst I got fantastic acceleration, my mid range cruise wasn't good and it was too easy to hit the limiter, as mentioned above.

14P seems to be the ideal pitch for me but as that's only available from Mercury (Blackmax) I settled for now on the Solas Amita 3 15P. (13.5x15)

With this prop, full fuel, water and 3 people I can turn around 5275rpm fully trimmed. If I run a 50% fuel load like last time and 2 people I can hit 5400rpm for around 30.5 - 31.0 knots.

A 12 or even 11 would have me worse off than the 13P and always on the limiter? As you know the WOT is 5150-5850 and I've been trying to aim for somewhere in between with a typical load of 100% fuel and 2-3 people as that's how I normally run the boat, whilst still leaving room if I carry less fuel and am on my own, not to bounce off the limiter."
 
I would stop switching between

I would stop switching between prop styles and concentrate on just a pitch change within one style itself. Pitch selection is always done by trial and error within a given style of propeller. Your complicating it by jumping to those different styles.
 
"Agreed which is why I have st

"Agreed which is why I have stayed with the Amita 3 range from Solas which are available locally.

As mentioned above I have tried the 13P and now running the 15P, same model etc.

I still haven't really understood the loading up issue related to a prop....is there anywhere that I can read up on this."
 
Loading up is related to runni

Loading up is related to running an engine at too low of an RPM in relation to the timing setting on the engine. See "Lugging an engine" in a web search.
 
"I'll try doing some testi

"I'll try doing some testing with the boat lighter, less fuel and people and see if it still happens.

I only have an 18.5 foot boat (waterline length)and perhaps the hull speed of the boat is just there at close to six knots (using a quick sqrt of hull waterlength in feet x 1.34).

Still seems strange that a modern ECU controlled 90hp engine can't cope with that and is bogging down and 'burping'."
 
An ECU can only handle so much

An ECU can only handle so much of a RPM/Timing missmatch and keep in mind that this is theory...Your problem may still be something different.
 
"Hi, I have 90 tldi , I switch

"Hi, I have 90 tldi , I switch key to open 3 red lights ffp pumps then start engine , tacho goes to 7000rpm on guage. Looking up trouble shooting and it seems to indicates ffp"
 
Re: "Update: I stil have my str

skip_mff said:
"Update:

I stil have my strange intermittent missing problem at 1400-2000rpm, and as it's now been quite some time I've asked the dealer to get on to Tohatsu for advice. ]

Hi, does any one know if this problem was solved for Skip and what the solution was?
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