Romany 162 Posted March 21, 2017 Share Posted March 21, 2017 on behalf of a friend down south... has a Jeanneau Gin Fizz (38' cruising fin keel, skeg hung rudder with a fixed 3 blade prop). No idea what size prop off the cuff. Normal start regime is to let it warm up and kick it in the guts to 2400rpm just because. Yesterday will not go beyond 1500rpm (unloaded) after warm up. Motoring from Nelson to Mapua it would not go beyond 1500 rpm. Cruising revs are 1500rpm underway but normally when asked - will push on to higher rpm and dig a bigger hole in the ocean.... Got to Mapua, tied up to the wharf for a cup of tea and a sleep, later in day started again but now would not run beyond 1000rpm. Injector pump rebuilt approx.1 year ago. Nothing else has changed - except the inevitable fouling. Oil pressure seems ok, fuel bowl clear of water, no warning lights, new diesel fill just recently. Boat gets used regularly. What could the issue be? Quote Link to post Share on other sites
Black Panther 1,589 Posted March 21, 2017 Share Posted March 21, 2017 I was going to say check the air filter, very similar to KM's thinking. Quote Link to post Share on other sites
wheels 543 Posted March 21, 2017 Share Posted March 21, 2017 Do I understand correctly that this is 1500RPM and now 1000 RPM in Neutral??Fuel flow or lack of tends to be the most common for such a symptom. Even if the filter bowl is clear does not mean the filter element itself is not blocked. That would be my first check.Blocked air filter will cause black smoke which is the tell tale sign of air starvation.Also check that the throttle cable is connected properly and moving the throttle lever on the inj pump all the way.Also, NEVER let the engine idle out of gear to warm up. Start engine, give it a minute to bring up Oil pressure and some warmth. I usually use the time of letting a mooring line go or lifting an anchor and then get the thing into gear and start motoring. Don't rev the guts out till you reach a decent engine temp. Usually by the time you motor out of the Marina, she should be sweet to go. If you let a Diesel warm under no load, you will cause it to smoke and go through Oil. 1 Quote Link to post Share on other sites
ballystick 72 Posted March 21, 2017 Share Posted March 21, 2017 How about a blocked exhaust? Also, thinking about petrol engines, is the timing advancing with possible seized or jammed advance mechanism if Perkins have that system. Quote Link to post Share on other sites
Kevin McCready 83 Posted March 21, 2017 Share Posted March 21, 2017 wheels advice is good. Before I knew better and before I knew of the dangers of carbonised engines, I took my boat to a well known Auckland marine engine company who failed to even look for carbonised engine. They ripped me off too in presenting an invoice which was a huge margin above their quote. Happy to provide details. email me if you're interested. Take out brackets, spaces etc {kevin 1] mccready) at[] gmail [[]]com] Quote Link to post Share on other sites
erice 732 Posted March 21, 2017 Share Posted March 21, 2017 intake air block should be first to check as it's so easy just take off the manifold if still can't rev, next check is fuel flow bleed the system esp. to make sure no air is in the injection lines maybe try and bypass all filters by hanging a cup of clean fuel above engine and gravity line to injection pump input if not air flow OR fuel flow restriction could be no compression on a first 1 cyl and now 2......... how's the coolant level now, has it been very low recently? has the engine recently overheated? can you get engine compression tested? my old 2cyl diesel would run ..........but not rev on only 1 firing cyl DPO had let a coolant leak overheat engine and spin out a crankshaft bearing killing compression in that pot https://www.youtube.com/edit?o=U&video_id=7ZO8ftgm6sM importing a new engine and self fitting was cheaper - faster - smarter? than rebuilding the old and helped the sale of the boat when a faster vessel appeared Quote Link to post Share on other sites
Island Time 1,235 Posted March 21, 2017 Share Posted March 21, 2017 Take off the air filter. Test. Change fuel filters, test. Then start looking at other more complex issues. This is the order I'd look in Fuel pump Injectors Compression Intake then exhaust manifolds Carbon build up ( head off) Etc etc Quote Link to post Share on other sites
marinheiro 352 Posted March 21, 2017 Share Posted March 21, 2017 After changing fuel filters and checking the screen in the fuel lift pump there is one further filter to check - the CAV rotary injector pumps generally have a little nylon "sock" filter on their inlet, remove the feedline from the secondary filter(s) and it can be removed for cleaning. Had this issue on my 6.354 Perkins, spent a month chasing my tail until a mechanic told me about the filter. 1 Quote Link to post Share on other sites
wheels 543 Posted March 21, 2017 Share Posted March 21, 2017 And that also reminds me, the Mechanical lift pump also has a fine mesh filter and I have had that block once also. Quote Link to post Share on other sites
Romany 162 Posted March 21, 2017 Author Share Posted March 21, 2017 Do I understand correctly that this is 1500RPM and now 1000 RPM in Neutral?? Yes Wheels that is what I believe I was told. He was speaking in an Auckland version of South Islandish though, so I could be mistaken. Quote Link to post Share on other sites
wheels 543 Posted March 22, 2017 Share Posted March 22, 2017 Sounds very much like Fuel or a throttle issue. So as already said, check those filters and the one in the lift pump and the rotary pump.If all checks OK, then as I said earlier, check the throttle cable and connections.Failing all the above, then something in the injector pump where there is a thing called the Fuel rack. This is what adjusts the amount of Fuel delivered to the injectors. The throttle is connected to the Fuel rack and also the Governor is connected to the Fuel rack. Simply, a Diesel increases/decreases the amount of fuel delivered in each squirt to regulate it's speed. Simple as that. The internals are fairly basic, but MOST CERTAINLY NOT, something any novice should attempt to pull apart. All the other scenarios, like compression, Injectors, restricted air etc and so on, all come with tell tale smoke signals. Fuel is the only thing that can cause an issue and maintain a clean Exhaust output at the same time. 1 Quote Link to post Share on other sites
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