Volvo AD41P RPM Issue

Pocho86

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Hi

So i got called to work on this volvo penta in a boat. Im a heavy equipment mechanic by trade. This engine is very simple and is just like working on the 4 and 6 cylinder cummins i work with but I heard volvo have their tricks.

So my customers boat has 208 hours. Its a Volvo AD41P with a duo prop. Out of the water with the props engaged or disengaged the WOT is about 4300rpm, this is way too high but thats not the issue though although id like to correct this to what it says it should be 3900rpm.

So Out of the water Props On or Off the engine revs to approx 4300rpm, the actual problem is when my customer is in the water with or without a load on it, it only can achieve approx 3300rpm. Ive went thru all the obvious stuff already. The boat fires right up and has no rough idle, lack of power(bogging down) or abnormal smokiness of any sort.

What ive done so far is:
- checked the fuel lines, the fuel tanks, the water fuel separators,
- checked all the banjo fittings for any screens cause I know on some construction equipment ive worked on have them
- Ive adjusted the advance screw on injection pump to see if that would help with issue and no changes in performance.
- I soap watered almost all the connections on engine, the after cooler and everything just for the hell of it and that didnt tell me anything.
- Visually inspected turbo spinning while running. Checked for end play, none. Minimal up and down play, no signs of impellars hitting housing.

Some one else a few month back had checked his after cooler and I guess that was good and clean. He claims the boat on his first 2-3 trips out it used too rev about 3900-4000 in the water before with or without weight and now he cant get to it. He did say that he cant hear any turbo sounds when hes running it but im not sure how audible the turbo should be on this engine in this boat as well.

Any idea or suggestions? Ive read about checking the exhaust side of the turbo for some sort of corrosion

If you need any more specific information, let me know. thanks
 

Pocho86

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Volvo AD41P RPM issue

Hi

Im a heavy equipment mechanic by trade, work on alot of cat and cummins engines. Its a similiar set up but Ive hear volvo got there tricks too. Got called to work on this cause the diesel engine side. My customers boat got 208 hours on this engine. Volvo AD41P with duo props. its a Typical 26' fishing boat, dry cabin up front, controls up front with deck on back. He is having a RPM issue.

His first 2-3 trips out he claimed he use to rev approx 3800rpm in the waters but now its not. In water with props on with any amount of weight he is only getting 3300rpm. Props off or on out of water it will scream at almost 4300rpm so ive ruled out the throttle linkage system and verified that it throws the full adjustment , i need to correct this high adjustment to its factory 3900rpm eventualy.

Ive checked all the obvious stuff already, throttle linkage, the fuel lines, fittings, valves, banjos for any screens, fuel tanks, and separators. Ive adjusted the advance screw on the injection pump, no change in performance. Some one a month ago I guess checked his aftercooler, i was told there is a screen in it and its all good and clean. I visually inspected the turbo intake side impellars and up and down and end play, ok. Ive soap water everything while it was running to see if there was any sort of leaks, nothing. He had changed the air , oil and fuel filters as well to see if any of that was causing it when he started having this problem and no change as well.

I feel like its either the turbo not helping enough under load or some thing to do with his prop set up but according to him it used to rev higher and according to his sources or information the set up he has is maxed out on prop size and blade pitch.

He told me he doesn't hear the turbo but being mounted on a boat and his set up im not sure how much turbo you will hear. Is there a way to test boost out of water? Or does it have to be i the water and what should it read

Help appreciated

If you need more specific info about boat let me know.
 

Scott Danforth

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what is the boost pressure? before the CAC and after
what is fuel pressure?
 

Pocho86

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I?m not a boatist so you need to be more specific about CAC and were you want me to check the boost at? What should my readings be?
 

Scott Danforth

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CAC is charge air cooler. you stated that you are a heavy equipment mechanic. you should know that. Its day one of the required learning for both Cummins and Cat training to become certified
 

alldodge

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Not saying your wrong, but in all fairness, the only place I've ever seen CAC has been with VP. Been on the Heavy Equipment Forum for as long as here and never seen it, all call them inner coolers.

Most cases for low rpm in these motors is clogged exhaust, turbo or fuel pressure. Running the motor with no load doesn't really tell us anything note worthy. The loaded rpm is the issue as you stated.

https://www.marinepartseurope.com/en/volvo-penta-explodedview-7742700-25-9409.aspx

Max exhaust temp TAMD41P at 3800 rpm ..................... 413?C (775.3?F)

Measuring exhaust back pressure


TAMD41H/M/P:
20?30 kPa (2.9-4.3 psi) (2000?3000 mm (79-118") wp)

exhaust.jpg
 

Scott Danforth

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its in the acronym section in the beginning of the cummins and cat service training guides from the classes I have been to. Cummins had a 200 page FUA (Frequently used Acronyms) that was also referenced. there were 2700 acronyms on the list when I left. CAT had a similar spec for their acronyms. it was also covered in the service literature at West Manitowoc (smaller crane division of Manitowoc Cranes from 1993-1998) in our crane training in the engine section

CAC is the generic category. within that is also JWAC (Jacket Water After Cooler), SWAC (Sea-Water After-Cooler), AAAC (Air-to-Air After-Cooler)

at Cummins there was an acronym for every aspect of the engines as well as the business side of thing

we had 4 meanings for VOC that were used - Voice of Customer, Volatile Organic Compounds, Vehicle Operating Costs, Verification Of Conformity. in cross-functional meetings it was funny to watch peoples faces from other departments

either way, check boost at manifold (after CAC) and at the elbow feeding the CAC. these two should be within 2" of WC (water column) of each other at full boost. typical CAC core pressure drop is about 1.5" if memory serves. high restriction is a plugged core, could be from oil leaking from the turbo shaft seal

so check exhaust back pressure (testing that AllDodge provided) and fuel system restriction as well
 

Pocho86

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Moderator Advice - Do the smart thing a use the Ignore feature.
 
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Pocho86

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Thank you for the information All Dodge, i plan to check the exhaust side of the turbo for any thing tat may be an issue. I did notice some oil directly below the air filter on the fly wheel housing so not sure if may be the turbo is leaking too much oil, it definately isn't smokey. Im trying to use all my heavy equipment diagnosing skills to determine the issue but what makes it different is that to load up the engine I have to have it in the water and this boat isn't one that's docked or anchored out in the ocean. It goes in and out via trailer. Ill keep you posted. Im also speaking with a Volvo mechanic on the other island thats been working Volvos only for over 30 years and he says im on the right path but nothing immediately comes to mind with my symptoms. Im trying to figure out if this guys outdrive set up is meant for this boat and engine.
 

alldodge

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Im trying to figure out if this guys outdrive set up is meant for this boat and engine.

If the boat was working fine prior to this issue then I would lean toward something happened. If the boat has always done this or started doing it after a prop or drive change then may be the wrong ratio or prop
 

QBhoy

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Check the turbo isn?t leaking at the exhaust flange. Check the actuator. Check for signs of unburnt fuel out the exhaust and into water. Those AD and TAMD 41 are known for all of the above. Need new or overhauled injectors every 500hours or so.
 
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