How do I adjust the throttle cable to hit hard stop max

[drude]

Apologies for the newbie question but I have a history of making a mess of things!

Engine regulator arm falls short of the hard stop when control set to full. Simple teleflex morse control linking to Yanmar 1gm10.

I have located the engine side connector and assume I need to shorten the cable by adjusting something here. But how do i do this?

Photo attached.

Many thanks for any pointers

Allister

 

[Minerva]

What RPM does the engine get in its current position? Have you looked at your engines power curve to ascertain what is the optimal cruising RPM for your boat / engine combination?

I don't think I have ever maxed the engine on a boat I've owned.

 

[drude]

Currently getting 2800 which pushes 25 foot yacht at 5kts on a good day. I understand continuous cruising revs but it would be nice to have the option of getting out of trouble with more power if needed.

 

[LittleSister]

You probably just need to adjust the length of the cable by means of the nut and sleeve you'll find on one end (probably the engine end) of the cable outer.

That assumes
a) you have you have sufficient travel on the engine control cable to move the lever from the low speed engine stop to the high speed stop. (In the unlikely event you haven't, make sure the cable is properly fitted to the control lever at the operating (non-engine) end); and
b) if you slacken or remove the cable and push the engine lever to its full extent the revs increases above 2,800. (If not, a lack of power or incorrect prop may be the problem.).

Note that the engine control is not a throttle - it doesn't adjust the amount of fuel (or air), it sets the engine revs. The centrifugal governor in the engine then automatically varies the amount of fuel supplied to the engine to reach and maintain the engine revs you have set in the face of whatever load (or lack of load) there is on the engine.

 

[Tranona]

Currently getting 2800 which pushes 25 foot yacht at 5kts on a good day. I understand continuous cruising revs but it would be nice to have the option of getting out of trouble with more power if needed.

Disconnect the cable from the lever on the engine to make sure it will go to the maximum and note where the position is. Reconnect and open the control lever in the cockpit to see if the lever goes to the same position. If the cable outer is clamped correctly in its bracket and the connector reaches the lever when it is in the closed position as it it is in the photo it should open the lever fully.

However low maximum revs is not directly connected to the position of the control lever. Revs are determined by the load placed on the engine by the propeller and if you can't get the rated 3400-3600 rpm then it is more likely because your prop is either fouled or is the wrong size. correct prop size is critical with a 1GM because of the meagre power available and the different gearbox reduction ratios available.

So details of the boat, and the gearbox ratio fitted - the choice is 2.2:1, 2.6:1 and 3.1:1. The first 2 are most common on modern sailing boats.

5 knots is good going with a 1GM at 2800 on a 25' boat (depending on its displacement) and if as I suspect the prop has too steep pitch you could probably up that by at least half a knot by accessing the extra couple of ponies available between 2800 and 3400.

If you post details of the boat and the gearbox ratio from the plate on top of the box there are computer programmes that will calculate a propeller size and expected speeds.

 

[saxonpirate]

Currently getting 2800 which pushes 25 foot yacht at 5kts on a good day. I understand continuous cruising revs but it would be nice to have the option of getting out of trouble with more power if needed.

2800 rpm should easily enough to push a 25' boat at hull speed. I think I'd be taking a look at the prop if I were you. That's what I'd be checking first anyway.

As for adjusting the throttle.. yes you can do that via the adjustment nipple on the end of the cable normally. What I would do though to check the amount of travel is just disconnect the cable and push the lever by hand to see if there is anything extra there. Remembering of course that the governor will only allow a certain maximum no matter what you do..

 

[LittleSister]

Have you looked at your engines power curve to ascertain what is the optimal cruising RPM for your boat / engine combination?

The engine's power curve will not tell you that. (If only life were that simple!)

Those curves know nothing about the load you are putting on the engine at those revs. You are unlikely to ever be using (other than momentarily when accelerating), the maximum power available from the engine at any particular revs, and so the fuel consumption figures indicated will not apply. The optimum revs for fuel consumption per hp won't necessarily apply at lower loads and hence engine power output, though it is likely to be in a similar ball park, but the difference in fuel efficiency at different revs will anyway be pretty much negligible for fuel economy purposes.

The faster you go, the greater the load (through friction and wave resistance), and that is a far, far more important factor than the particular revs (or even the particular engine) on fuel consumption. (Or to look at it another way, the more hp you need, the more fuel you will use.) So, broadly speaking, the slower you go, the more 'economic' it will be.

The efficiency of the prop at different prop speeds and differing loads (e.g head or tail winds, waves, etc.) at each of those speeds will be another factor in 'efficiency'. Again, not factored into the the engine manufacturer's graphs.

In real life, one will tend to cruise with the engine around medium-ish revs, any slower is too tedious, and any faster is too noisy, vibratory and thirsty.

 

[LittleSister]

However low maximum revs is not directly connected to the position of the control lever. Revs are determined by the load placed on the engine by the propeller and if you can't get the rated 3400-3600 rpm then it is more likely because your prop is either fouled or is the wrong size. correct prop size is critical with a 1GM because of the meagre power available and the different gearbox reduction ratios available.

I disagree. The position of the engine control lever does directly set the revs. That's exactly what it does, and that is all that it does. The automatic governor will provide as much or as little fuel as is required to maintain the revs the control lever has set.

The engine will only fail to reach the selected revs if the load exceeds the power available at those revs, due to unusual circumstances e.g. very heavy fouling, very powerful headwind, engine fault or incorrect propellor selection.

If the load is somehow reduced so that it falls below the power potentially available from the engine at those revs, the gearbox is put in neutral, or the propellor falls off, it won't actually rev any faster! The automatic governor will simply reduce the fuel supplied to the engine.

Try it and see!

 

[Tranona]

Read it again. he was asking why he only gets 2800rpm. I was referring to the actual maximum he is getting, which is 800rpm lower than the maximum permitted by the governor. So the lever is calling for 3600 but is only getting 2800. HIS maximum is therefore not directly connected to the position of the control lever. Then I explained what might be causing that, just as you have done. We are not at odds, just expressing in a different way.

 

[drude]

Thanks for the replies. Is it common practice then to restrict the regulator arm to cruising rpm ?

 

[Tranona]

Thanks for the replies. Is it common practice then to restrict the regulator arm to cruising rpm ?

No. The maximum rpm is set by the governor and under no load will be restricted to 3600rpm - but not producing any meaningful power. if the engine is running properly and you are not achieving rated maximum then almost certainly as I suggested earlier it is because the propeller is fouled or it is too "big" - that is either too large diameter or too steep pitch or both. Has it always been like this or has it changed?

When an engine is installed the installer looks at the data on the boat - essentially, length to estimate hull speed potential and displacement then calculates the optimum propeller to achieve hull speed with the maximum power available from the engine and the shaft speed determined by the reduction ratio.

A Sadler 25 for example with a waterline length of just under 20' and displacement of 4000lbs has a hull speed of just under 6 knots and requires 9hp to achieve this. The most common modern engine fitted to the boat is a 1GM with a 2.65:1 reduction and a 13*10 propeller. To achieve this speed the engine will run close to maximum rpm. Cruising speed is normally at 75% maximum revs (2700) and 5 knots. If you look at the propeller power curve of the engine it is producing approx 6hp.

If your check on the lever shows that the cable is pulling it to its full extent then you need to look at your propeller. As an approximation 1" change in pitch or diameter changes engine revs and therefore power available by 300rpm. You are 800rpm short of maximum.

Hope this makes sense

 

[Bilgediver]

It could be that you need to make the adjustment attempt cockpit end. . The throttle lever may have a choice of hole positions where the cable connects to the lever. If there is another hole in the arm at a greater radius than currently connected you may get the desired result.

 

[Refueler]

Its funny actually .... the 2GM I have in my 38 - max fwd / astern is all there .... but neutral is so vague ....

The box 'clonks' as if the gear has disengaged - but it seems that it hasn't .... you then move it a touch more and it goes other way ... Doesn't matter which way you go ... astern to neutral ... ahead to neutral ...

The lever has no marking to reference it to ... at present it is not vertical after last docking ... its about 30 deg to stern ...

It can make docking interesting ...

 

[Bilgediver]

Its funny actually .... the 2GM I have in my 38 - max fwd / astern is all there .... but neutral is so vague ....

The box 'clonks' as if the gear has disengaged - but it seems that it hasn't .... you then move it a touch more and it goes other way ... Doesn't matter which way you go ... astern to neutral ... ahead to neutral ...

The lever has no marking to reference it to ... at present it is not vertical after last docking ... its about 30 deg to stern ...

It can make docking interesting ...

It gets even more interesting if the throttle has a neutral switch in the start circuit.

 

[Refueler]

Today after few jobs - tried gear lever while alongside ....

Neutral seems to be with lever about 25 degrees angled aft ... NOT straight vertical.

There is a small push button in lever centre to disengage .... it pops out at that 25 degree position ... so seems to be what is neutral point ...

 

[Bilgediver]

Today after few jobs - tried gear lever while alongside ....

Neutral seems to be with lever about 25 degrees angled aft ... NOT straight vertical.

There is a small push button in lever centre to disengage .... it pops out at that 25 degree position ... so seems to be what is neutral point ...

Maybe need to do some tinkering at the gearbox end to get middle for diddle...Or neutral

 

[penfold]

Today after few jobs - tried gear lever while alongside ....

Neutral seems to be with lever about 25 degrees angled aft ... NOT straight vertical.

There is a small push button in lever centre to disengage .... it pops out at that 25 degree position ... so seems to be what is neutral point ...

The lever should have a detent at neutral; some levers appear to have them at the point of gear engagement also but that may be the gearbox rather than the lever unit. The detent mechanism(a sprung ball bearing engaging in notches etc) may well be clogged with dried grease and/or corrosion. The lever may have been set at a funny angle if having it upright meant full throttle wasn't possible due to the cockpit moulding getting in the way.

 

[Tranona]

Today after few jobs - tried gear lever while alongside ....

Neutral seems to be with lever about 25 degrees angled aft ... NOT straight vertical.

There is a small push button in lever centre to disengage .... it pops out at that 25 degree position ... so seems to be what is neutral point ...

The lever is on a spline on the shaft so has probably been put on 25 degrees out of vertical.

 

[Refueler]

The lever is on a spline on the shaft so has probably been put on 25 degrees out of vertical.

Thats fine and I was aware .... but my point in posting was that selecting neutral is 'vague' ....

My single lever on Superanne - most definite 'feel' as it goes in / out of gear .... but the 38's is too vague and easy to go past neutral ...

When previous owner motored the boat with us to fuel dock - it was seen then - he had trouble finding neutral.

Its another silly job that will be sorted over winter.

 

[scottie]

You are perhaps trying to sort several problems at the same time
the lever as said is on a spline and as such the control doesn’t care where in the 360’ it’s placed or even what way the control is oriented
when Morse destruction tested the original TX the spline in the handle was initial point of failure and their test completed with one of their own i don’t recall the final outcome of the test other than it was more than adequate
The control has an internal detent which should align with the neutral detent if fitted in the box but as I recall is pretty vague as I remember this can me set up and adjusted with throttle or speed adjustment cable disconnected
the speed cable should be adjusted to ensure that the full travel at the engine connection is available but will need to allow for the additional travel when going from neutral to in gear caused by the arc of the cable end this requires a lost motion device usually a spring to allow the engine to stay at idle before gear is engaged
it is worth getting hold of the fitting instructions for the control to see exactly and read in conjunction with engine instructions
check if the cable has been replaced an not fitted correctly and if the spline in the handle is worn and this is only place it doesn’t slip