Break in for Tohatsu MFS60

Snakedoctor · 16 July 2023, 06:46

Hi All,
1st time poster as I generally lurk around the forum trying to gain as much info as i can. Just purchased a brand new Tohatsu MFS60 Long shaft (EFI) from a Tohatsu dealer in the Netherlands and have run it for a maximum of 1 hr along similar guidelines per the manual but not same. For the 2nd hour run in, I could not get the engine to rev beyond 4000 rpm. Per the manual, the engine is rated for a max of 6000 rpm. I tried WOT but the engine seems to restricted to 4000 rpms. Is this by design? Do I need to run the engine exactly per the manual for the power to be unrestricted by the engine or should I request the dealer to look at the engine as I m not sure if this is safety feature bult into a modern engine as my last was a 23 yr old. Yamaha Thank you

chipko · 16 July 2023, 08:56

Hi and welcome.

Whilst not familiar with that exact engine I don’t think any motors restrict revs during the running in period. Many do however restrict revs when not in gear. In gear, full revs should be available whether running in or not and the over rev limiter will kick in around 6000-6300rpm typically.

If it won’t rev past 4000rpm, assuming no mechanical issues, the most likely cause may be it’s over propped for the boat size/loading. What boat is it on and do you know the propeller pitch.

Snakedoctor · 16 July 2023, 10:33

Quote:

Originally Posted by chipko

Hi and welcome.

Whilst not familiar with that exact engine I don’t think any motors restrict revs during the running in period. Many do however restrict revs when not in gear. In gear, full revs should be available whether running in or not and the over rev limiter will kick in around 6000-6300rpm typically.

If it won’t rev past 4000rpm, assuming no mechanical issues, the most likely cause may be it’s over propped for the boat size/loading. What boat is it on and do you know the propeller pitch.

Hi Chipko, Thank you for the welcome and reply. No idea about the prop. It came delivered standard with the boat which is a 450 kg fiberglass tender with a flat bottom so my thinking was with that weight to power ratio it should plane easily but what stuck out was the rpm range. I reach out to the dealer to ask these details. My other boat is a rib with a 22 year old Yamaha 40hp (4 stroke with Carbs) and that literally takes off at 2500 rpm and planes and I am / was under the assumption that newer engines have built safely. The manual states that “ full power is available after 10hrs of run in” which I presumed meant the engines software actually counts down 10hrs before derestrcting power. Not sure if I am overthinking this or its just the English from a Japanese manufacturer

Fenlander · 16 July 2023, 10:57

Like Chipko I don't know this outboard but I have looked at the user manual online. I note it says to keep to 3000rpm/half throttle until after 2hrs have been covered, then three quarter throttle and one minute bursts of full throttle in every ten mins during the 2-3hr period. You should not be trying for 4000rpm until after 3hrs.

I think all the references in the running in table are to your operating at the stated speeds not the outboard having any control over this.

I see the limp-home rev restriction is 3000rpm if a fault is found so if you are reaching 4000rpm then I don't think you have any faults as such.

So like Chipko I think this sounds a bit like the outboard being incorrectly over-propped hence not pulling higher revs... and of course if you really are only just over 1hr on the engine then you have more running in to do before you return to trying these higher speeds... the engine could still be a bit tight??

69cmw · 16 July 2023, 11:10

I bought a new BMW bike recently and you can’t get full revs until it’s been back to the dealer for its 600 mile running in service, it’s hits a limiter around 8000 rpm rather than the 12000 rpm it does after the service 🤷*♂️

Snakedoctor · 16 July 2023, 11:30

Quote:

Originally Posted by Fenlander

Like Chipko I don't know this outboard but I have looked at the user manual online. I note it says to keep to 3000rpm/half throttle until after 2hrs have been covered, then three quarter throttle and one minute bursts of full throttle in every ten mins during the 2-3hr period. You should not be trying for 4000rpm until after 3hrs.

I think all the references in the running in table are to your operating at the stated speeds not the outboard having any control over this.

I see the limp-home rev restriction is 3000rpm if a fault is found so if you are reaching 4000rpm then I don't think you have any faults as such.

So like Chipko I think this sounds a bit like the outboard being incorrectly over-propped hence not pulling higher revs... and of course if you really are only just over 1hr on the engine then you have more running in to do before you return to trying these higher speeds... the engine could still be a bit tight??

Thanks Fenlander. It could most probably be the prop as i did not consider it before or it could be limited as the next poster states. I ll reach out to the dealer. Greatly appreciate your reply. Thank you

Snakedoctor · 16 July 2023, 11:31

I ll ask Tohatsu directly. Thanks.

chipko · 16 July 2023, 11:50

It’ll not be electronically limited during running in, despite the BMW reference.

Doesn’t sound like a fault either as the low speed ESG, as Fenlander stated, is set at 3000rpm and the high speed ESG kicks in at 6200rpm. A warning buzzer/light would also be on if low speed ESG is triggered. My money would still be on prop size.

Hope you get it sorted, they are nice motors.

PS: For info we run a 13” or 14” (13 for towing) pitch prop on our similar sized Mariner 60 on a 600kg 5m rib.

Fenlander · 16 July 2023, 13:04

The OP doesn't say what the exact boat type is but from his comment that its 450kg fibreglass with a flat bottom it sounds a bit of a heavy draggy thing that should have been pitched below the standard.

Snakedoctor · 16 July 2023, 13:08

Quote:

Originally Posted by chipko

It’ll not be electronically limited during running in, despite the BMW reference.

Doesn’t sound like a fault either as the low speed ESG, as Fenlander stated, is set at 3000rpm and the high speed ESG kicks in at 6200rpm. A warning buzzer/light would also be on if low speed ESG is triggered. My money would still be on prop size.

Hope you get it sorted, they are nice motors.

PS: For info we run a 13” or 14” (13 for towing) pitch prop on our similar sized Mariner 60 on a 600kg 5m rib.

Just went and and started up the motor and revved it in free. The motor revs to the maximum (8000 rpm) so you are right if it were limited it would cut out at 4000 rpm. I am now doubting if I revved the motor all the way while in gear as I had a non Tohatsu RC installed for aesthetic vanity and it goes all the way down ( from 12 0clock position to almost 7 o’clock position ) whereas with the Yamaha factory RC its 12 at idle and 3 at max. I ll have to check this out tomorrow as its blowing a hoolie today.

Snakedoctor · 16 July 2023, 16:03

Update - could not wait so went out and pushed the throttle all the way down. The boat took a while before it came out of the hole and planed and once on plane the rpms and speed went up. I did this for a short burst of about 2 minutes twice and as its gusting at 70kph and with the hood up it was not safe. Perhaps the prop can be optimized to get better performance but as Fenlander stated it’s a bit of a barge and not a rib. Thank you all for the suggestions