Continual problems "hunting" Sole mini 26

[steve1963]

I posted this problem some time ago, and received some helpful replies. I still have the same problem, and want to see if I get any more feedback before calling in an engineer.

Basically, the problem is that, when under load, my Sole mini26 very often hunts if I try to increase the revs. The problem is intermittent, and doesn't seem to follow any recognisable pattern. The problem has existed ever since I have had the boat (several years). The engine is in good overall condition, with few hours. When hunting, the engine never actually stops, and it only happens when under load (If I put it out of gear, and give it full revs, it responds to full throttle). I am convinced that it is NOT an exhaust problem, as I have replaced all the exhaust hose, and it is in good condition. I also do not think it is a problem with air in the system, as I have bled it, and it doesn't solve the problem. I also do not think it is dirty fuel, as I installed a fuel polisher, and the fuel looks to be in good condition.

I strongly suspect that it is a problem with the govenor. Anyone know of a way to test this? Anyone had similar problems? Any other comments?

 

[Bilgediver]

If the engine is not in gear and you move the speed control slowly up to full and then back to slow does the engine follow as the lever is moved without delay?
If the engine is in neutral and you engage forward gear does the engine go into gear and run at a slow speed steadily both in forward and astern?
if the engine is idling in gear steadily and you increase the revs by 200rpm does the engine increase and run steadily?
When the engine hunts at full speed what range of speeds is it hunting between.
Is your boat fitted with a direct drive via shaft to propeller or des it have a stern drive with leg?


https://www.solediesel.com/datos_publicos/Manuales/U_FA0966_EN.pdf

 

[steve1963]

Hi Bilgedriver; to answer your questions:

If the engine is not in gear and you move the speed control slowly up to full and then back to slow does the engine follow as the lever is moved without delay?
If the engine is in neutral and you engage forward gear does the engine go into gear and run at a slow speed steadily both in forward and astern?

Yes to both, I think

if the engine is idling in gear steadily and you increase the revs by 200rpm does the engine increase and run steadily?

Yes. The engine will usually respond correctly to the throttle, but, when the problem mansifests, the engine will begin to hunt after some minutes of running at high revs.

When the engine hunts at full speed what range of speeds is it hunting between ?

It will hunt between 600/700 to-3000+ revs at full throttle

Is your boat fitted with a direct drive via shaft to propeller or does it have a stern drive with leg?

direct drive via shaft to propeller

 

[roaringgirl]

If it does it after some time at higher revs, have you considered fuel starvation?

You could check it by running the engine from a jerry can raised above the height of the engine, if this solves the problem, you know it's starvation - start checking filters, checking for air leaks and maybe look at your lift pump...

 

[Bilgediver]

If it does it after some time at higher revs, have you considered fuel starvation?

You could check it by running the engine from a jerry can raised above the height of the engine, if this solves the problem, you know it's starvation - start checking filters, checking for air leaks and maybe look at your lift pump...

Roaringgirl's suggestion is a good one. However if it is not a fuel issue then the engine is responding to a change in load which could be due to a slipping clutch, coupling or prop on shaft at higher speeds. From your earlier answers it seems the governor is fine.

 

[bristoljim]

Roaringgirl's suggestion is a good one. However if it is not a fuel issue then the engine is responding to a change in load which could be due to a slipping clutch, coupling or prop on shaft at higher speeds. From your earlier answers it seems the governor is fine.

Tank vent restricted ?? try a run with filler cap off.

Jim

 

[Topcat47]

+1 for vent problems. If it only happens after a protracted period of running at full throttle, it's likely that enough air is not being admitted to the due tank to replace the volume of fuel being used. While the engine hunts, air will still be rushing in through the vent, which would explain why it stops after a while. Running with the fuel cap off is not a good idea unless the opening is protected from water ingress. You might try it with one of those temporary fuel caps sold in petrol stations if the sea state is flat and see how it goes. They allow air to flow freely.

 

[steve1963]

Thanks to all for replies and suggestions.

My feeling is that it is unlikely to be a clutch problem: The hunting is "down" rather than "up". In other words, If I set the throttle to a position for, lets say 2200rpm, the revs drop off from here, and do not race up to greater than 2200rpm. If the clutch was slipping, wouldn't it tend to race up? Also, if it was a clutch problem, then I would expect it to get progressively worse over time, whereas although this problem is intermittent, it does not appear to be getting worse (several years now!)

Thus, my feeling is still that it is a fuel feed problem, but not quite sure where.

The fuel cap idea is interesting and easy to test

Any further feedback is more than welcome!

Steve