tohatsu mfs 30B won't make power

[aircoastie]

I've been reading lots of posts about Tohatsu outboards that won't make power and most of them discuss cleanout of carbureted models... my 30 is EFI...

I've gone through all of the fuel lines I can get at and made sure they're clear, changed the spark plugs and added "gunk out" to the gas and ran about 4 gallons of it through the engine and it still doesn't make power anywhere near what it did when new... this is my first outboard, so I'm doing my best to learn how to keep it running well, but I'm falling short so far...

- the engine starts perfect
- it does surge at idle
- I bought the engine four yrs ago new & it was real powerful out of the hole & at top end... now it's sluggish out of the hole and it struggles to get my flat bottom plywood skiff on plane with anyone besides me in the boat.
- factory prop (at least I keep that running well!)

I've talked about it with other "boat people" and have got several suggestions:

- new gas tank line
- replace high pressure filter
- use additive for each fill up
- use higher octane gas (I was told the 87 octane was fine)...
- air filter?

I still use the boat to fish and cruise islands, but it would be nice to get my power and top speed back... Any thoughts? Thanks.

 

[TOHATSU GURU]

Re: tohatsu mfs 30B won't make power

Take it into a dealer, let them hook it up to the software and run the tests. It's either your fuel system or something that the software can pick up. Chances are it is dirty injectors, but without actually testing it's all just a guess.

 

[aircoastie]

Re: tohatsu mfs 30B won't make power

Thanks... I was hoping it was something I could pinpoint... computers!

 

[TOHATSU GURU]

Re: tohatsu mfs 30B won't make power

You can buy the software and computer harness, but it's not worth it for the individual.

 

[pvanv]

Re: tohatsu mfs 30B won't make power

Right. In addition to the Factory service manual, you would order Part# 3AC729200M $325.00 (DIAGNOSTIC KIT - 25B/30B EFI 4-STROKE), install the software on your own laptop computer, connect the harness to the motor, and then you would need to learn how to interpret the information displayed on the laptop. More cost-effective to have a dealer work on it.

 

[Pedorro Ediondo]

Re: tohatsu mfs 30B won't make power

I've been reading lots of posts about Tohatsu outboards that won't make power and most of them discuss cleanout of carbureted models... my 30 is EFI...

I've gone through all of the fuel lines I can get at and made sure they're clear, changed the spark plugs and added "gunk out" to the gas and ran about 4 gallons of it through the engine and it still doesn't make power anywhere near what it did when new... this is my first outboard, so I'm doing my best to learn how to keep it running well, but I'm falling short so far...

- the engine starts perfect
- it does surge at idle
- I bought the engine four yrs ago new & it was real powerful out of the hole & at top end... now it's sluggish out of the hole and it struggles to get my flat bottom plywood skiff on plane with anyone besides me in the boat.
- factory prop (at least I keep that running well!)

I've talked about it with other "boat people" and have got several suggestions:

- new gas tank line
- replace high pressure filter
- use additive for each fill up
- use higher octane gas (I was told the 87 octane was fine)...
- air filter?

I still use the boat to fish and cruise islands, but it would be nice to get my power and top speed back... Any thoughts? Thanks.

We have the same motor branded by Mercury as their 30 EFI and just had the identical problem, Merc has a service bulletin out about the problem. They recommend installing a jumper between the negative battery cable ground and the port ground on the front of the motor. The battery cable grounds to the motor block through the starter frame and starter bolts, and the ECU grounds at the front of the engine. Corrosion introduces resistance, the ECU gets messed up, and the engine starts to surge at idle, misfire under load, and stall out. We noticed a voltage between the remote control and the engine block, about 2 V AC at a frequency of 40 to 100 Hz varying with engine speed. Removing all the bolts, cleaning and anti-seize, and torquing the bolts made the problem go away. Computers aren't that difficult, you just have to be extra-careful about electrical connections. Sure beats taking a carb off an Evinrude, cleaning it out, putting it back on, and having to take it back again.

 

[Pedorro Ediondo]

Re: tohatsu mfs 30B won't make power

Oh, I forgot the partly clogged injector that also caused problem, especially surging. Running cleaner won't remove solid obstructions. Only the top injector was plugged, only the bottom holes--2 of 6 holes were plugged. Probably from the motor sitting too much. Diagnosed by running the engine at about 2000 rpm removing one injector connector at a time and noting how much the rpms dropped. Replaced injector, $70, ran great.