You should also try to rev the engine with it out of gear. If it has the same problem of reaching full RPM then fuel and air delivery are nearly to only possible culprits.
A bad or weak governor spring would be indicated by an engine that has a tendency to over speed or hunt. Pulling the throttle faster applies pressure to open the fuel rack and provide more fuel. More fuel create more RPM and the governor the creates a feedback force that resists the fuel rack. The governor tries to slow the engine whereas the throttle tries to speed it up. Without the governor the engine will tend to race, have high RPM, limited throttle control, and is lively to overspreed. When you get to 2100 RPM do you get heave black smoke? If you do the engine is getting plenty of fuel but not enough air. Have you checked or simply removed the air cleaner? When was the last time the backlash was checked on the lifters. I can walk you through it if you don't know. If you're not getting black smoke, are you getting any change in smoke? Are you getting a correlating loss of power or stumbling? Or is it just not going faster? Was it not able to push the boat at normal full speed. Are you confident in the accuracy of the RPM gage. You can get a laser tach from Amazon for less than $20 to confirm the RPM. As the high pressure fuel pump and fuel injectors age they have springs that get weak. Weak pump springs will allow the tappets to "float" and not achieve a full intake stroke of fuel....causing a low fuel condition resulting in lower RPM. If the injectors are dirty or have weak springs they won't achieve full fuel pressure before injection and may even leak a small amount into the cylinder before TDC. This is probably good more likely to cause detonation (ping or knock), not exacly low RPM but none the less is sub optimum operation. Have you checked the oil for fuel dilution? The fuel lift pump is driven off a cam and if the diaphragm cracks or tears it will leak fuel into the crank case. This may also let crankcase pressure into the high pressure fuel pump...reducing fuel delivery and RPM. Pull the dip stick, drop some oil on a paper towel. Smell it for diesel smell. Wait and observe for a halo. Especially if you have red diesel the halo is seen as the clearish red halo around the black oil spot. If all of that checks. Then you need to get a little more invasive. A compression check is in order. I can walk you through it and provide parts(tools). It is definitely doable as DIY but you got some investigation to do first. Let me know. Reach out with a PM and we can talk. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD Jun 26, 2022 09:39:09 Robert Abbott via CnC-List <cnc-list@cnc-list.com>: > > Went to take the boat out Friday for a short sail .....motoring out heading > into a12 knt breeze....started to increase the RPM's and found the engine > wouldn't rev about 2,100 RPM's ....marine diesel's are not supposed to be > that complicated but they are to me. I wouldn't know where to start to > trouble shoot....getting a mechanic to deal with it this week. I spoke to > him and told him the situation and he thinks it is a fuel problem....engine > not getting enough fuel....my fuel tank and fuel should be clean as I had the > bottom of it replaced 2 years ago and the 2 fuel filters replaced. He thinks > one or both of the filters are restricting the fuel flow.....I hope he is > right but I don't think so. > > Possibly many are causes....restricted fuel injectors, fuel pump, etc. > ....the engine has never been serviced in the 16 years I have had the boat > > Any insight or guidance to help greatly appreciated. > > Rob Abbott > AZURA > C&C 32 - #277 > Halifax, N.S. >
