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Re: 3116TA not reaching RPM

Update: replaced turbo on engine that was only getting to 2000 rpm and it corrected the issue completely. Thank you!
New member

Re: 3116TA not reaching RPM

Update:  Checked throttle cable travel, was OK.

Removed air cleaner assembly on engine that was only getting to 2000 RPM and found the turbo fan seized.  Cannot move it at all.  Installing new (reman Caterpillar) turbo later today.


The thought is with the new turbo, it will correct the issue and both engines should get up to the proper RPM.  Still have not cleaned the aftercoolers, but I am running SAE30 oil.  Was planning to do aftercoolers after I decommission the boat later this year with other maintenance.  Need to find a shop that can clean and pressure test them. I know CAT recommends replacing them every 6 years but my bank account is rather bone dry at this point.


A bit frustrated I had just paid H.O. Penn Newington to come down and check out the engines and their expert did not notice the turbo was seized.  When you pay $2000 for 4 hours of work you hope to have some expert help.


Will update once turbo is on.  BTW, the reman CAT turbo is the complete snail shell assembly with the turbo in it, not just the turbo itself as you would buy from Borg Warner or others.  



Regular Contributor

Re: 3116TA not reaching RPM

The engine that is only reaching 2000 rpm is most likely holding the other engine that gets to 2500 rpm back or overloading it due to low power from the engine only getting to 2000 rpm. These MUI 3116 / 3126 engines are prone to plugging the air side of the aftercooler and restricting air flow . Cat Special Application Engine Oil (SAEO) is specified for these engines which is a single viscosity oil that prevents the plugging problem. Regular cleaning of the aftercooler is also speciifed in the Operation and maintenance manual. Although this problem is normally indicated by the presence of black smoke in the exhaust it could be that the engine is unable to produce sufficient boost pressure and therefore is being fuel limited by the Fuel Ratio Control.

Suggest removal and cleaning of the aftercoolers would be a place to start provided fuel pressure is ok and air cleaner is ok.


Super Contributor

Re: 3116TA not reaching RPM

Do the throttle cables advance the governor lever all the way to the stop? This can be checked with engines off.
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Accepted Solution

3116TA not reaching RPM

Have two 3116TA engines that don’t reach 2800 rpm. One reaches 2500, the other 2000. Serial numbers are 4KG05016 and 4KG04974. Just had turbo replaced with CAT reman on one engine due to sound from turbo (the one that gets to 2500 rpm). Bottom of boat has new paint and is clean, props are factory pitch and such, boat not overloaded. No smoke at all from engine with new turbo, slight black smoke from engine that only reaches 2000 rpm. Temp and oil pressure seem normal on both. New fuel filters on both, primary and secondary. I have had a couple diesel mechanics out and they don’t know 3116 engines well enough to diagnose. Had CAT out once and that mechanic didn’t seem to think it was an issue “if temp and oil pressure ok, don’t worry about it”. I don’t want to damage the engines and have heard running less than rated rpm will damage the engines. I am in Connecticut in Westbrook. Need help, please advise. Happy to hire someone who knows the engine and is talented.