Engine not making as much power as it should [Westerbeke W50]

[thematt]

Hey folks,


Looking for some ideas on what to check for on an otherwise good, but old, surplus engine not quite making the power it should.


The short story is, instead of repowering my Tartan 42 with a new engine, due to circumstances and engine install angle + v drive etc, when the original W50 started to die, I dropped a 'good running' surplus in.


The engine fires great and runs great, but doesn't quite seem to have as much power as it should.



It's turning a 16x10x3 blade Flexofold, which should be doable to it's rpm of 3200 with it's 41HP. However in sea Trialing at cruising weight and medium clean hull, I can only get ~2750rpm before I start to see a bit of smoke and temps creep up. backing off to 2400 rmps temps normalize at 184ish. I tested in pretty ideal, but not perfect, conditions both against and with the little current that was there. I am able to make 'just about hull speed' ±.3 kts. I only have SOG, and not through the water so I was solving for current.



This all seemed like classic over prop, but got a second option from flexfold who said my current prop is ideal.


So that said, on what should be checked that could be causing a lack of power? Am I overly concerned about nothing?



One thought I had was maybe valve clearance needs adjusting, since I have no idea when this was last done. Could that be it?



I've checked the throttle linkage has full range already.


Thanks for the help!

[rslifkin]

When it starts to smoke and the temps start to climb at 2750 is that actually the max RPM it'll get to? Or will it rev higher when pushed?

[thematt]

2750 is the Max with throttle wide open.

[FPNC]

Run a cylinder compression check.

[maine50]

What is the shaft RPM? i.e. What is the transmission ratio? I'm running a flexofold 17dia 3 blade with 12 pitch and I'm over pitched with a Beta 38 in exact same hull.(Tartan 41/43). No smoke or overheating.

[thematt]

Transmission ratio is 1.88, previous owner installed. That'd make shaft rpm ~1460 at peak.


Do you also have the 17 degree install angle on your engine? Mechanics were hesitant to install a beta and said absolutely not to yanmar at that angle.

[skipperpete]

With the original driveline and propeller you had no problems reaching maximum rpm under load and no overheating? If thats the case, logically the engine is low on power and now overpropped relative to that power loss. Are there any parasitic loads that have changed? High output alternator? Dual alternators? Hydraulic pump? If the answer is no then you have some troubleshooting to do and as you mentioned, adjusting the valves is a reasonable starting point but there’s a whole list of items that need to be checked and either verified or dismissed as causes of your black smoke and overheating…. Mixer elbow, coked up exhaust or intake ports, injector problems, and possibly a leaking head gasket… its all just a guess until you do some thoughtful testing and investigation.

[thematt]

Thanks for your feedback!


I was a novice new owner when I pruchased the boat and babied the old engine where I shouldnot have. In short: I don't know what the old behavior was and am making up for past mistakes by guessing in the dark, more or less.



I have a 'medium' output alternator. A balmar 6 series I have d tuned to 70 to 80 amps to support the v belt. The alternator was floating when testing, so there was some load, but not the full ammount.


Exhaust elbow is brand new custom made for the surplus motor swap. A compression test would be great but time consuming and costly, my old engine had issue including head gasket, while not perfect for diagnosis, this motor starts up so easily and sounds way better that I would put that low on my list.


There is on a small ammount of smoke at 2750rpm, could it be the over heating is simply an over taxed motor without the ability to spin the water pump">raw water pump at speed? Certainly a coolant flush would be helpful for this old engine.


I appreciate the sanity checks. I wouldn't want to overlook something obvious.

[Wotname]

Skipperpete nailed it with there’s a whole list of items that need to be checked and either verified or dismissed as causes of your black smoke and overheating.

You have to start with a logical and thoughtful approach rather than throwing ideas (and money) willy nilly at the engine hoping something will suddenly make it good.

The usual (and IMO, the best) approach is start with the low cost items first and then proceed one by one towards the more difficult aspects to check.

However, first I believe you have 2 different problems and you should keep them seperate in the fault analysis approach.

1. Lack of power
2. Potential overheating.

While they might be caused by the same fault, it would be more usual to find that they are seperate faults. The cooling system should be able to remove all of the heat when the engine is running at full power. If it is isn't, then there is fault in the cooling system, not in the engine.

1. Probably caused by lack of fuel (injection issues) or lack of compression (valves / rings) but it could be air (i.e. exhaust restriction causing too much exhaust back pressure). Check the valve lash, inspect all of the exhaust system for obstruction, have the injectors tested, compression test, exhaust back pressure checked, have injection pump tested.

2. Clean the heat exchanger, check thermostat, rebuild raw water pump, coolant flush.

[thematt]

Thanks a ton folks. Certainly have given me ideas and I have more info to fill in:

For the coolant system:

Heat exhanger is clean and tubes inspected the best I am able, raw water pump was just rebuilt. Thermostat and coolant I would considered suspect / need cleaning including raw water loop pre engine (v drive).

Your list for the engine fuel system will be my guide. The exhaust system will be easy to check. No idea when the water mufler was last checked. The hoses are newish (5-10 years).

[skipperpete]

Originally Posted by thematt

Thanks a ton folks. Certainly have given me ideas and I have more info to fill in:

For the coolant system:

Heat exhanger is clean and tubes inspected the best I am able, raw water pump was just rebuilt. Thermostat and coolant I would considered suspect / need cleaning including raw water loop pre engine (v drive).

Your list for the engine fuel system will be my guide. The exhaust system will be easy to check. No idea when the water mufler was last checked. The hoses are newish (5-10 years).

Oh, I forgot to mention the Tacho, I guess that its probably the same head but is the SOURCE still the same. If it picks up the AC pulse from the replacement engine alternator there’s a vague possibility that the tacho needs a re calibration if the characteristics of that alternator have changed, ie pulley ratio. Could it be as simple as a low reading tacho? Unlikely , but worth considering.

[Wotname]

One data point - the max engine temperature should not exceed the fully open thermostat temperature or if it does, it should only exceed it by a few degrees at the most.

Pull the thermostat and measure it's fully open point. If it is close to its designed temperature, use this number as a guide to determine if the cooling system is working properly.

[rslifkin]

Originally Posted by Wotname

One data point - the max engine temperature should not exceed the fully open thermostat temperature or if it does, it should only exceed it by a few degrees at the most.

Pull the thermostat and measure it's fully open point. If it is close to its designed temperature, use this number as a guide to determine if the cooling system is working properly.

Agreed, normal temp range is up to the thermostat fully open temp. However, the spec temp is usually the temp where it starts to open. Fully open is 15-20 degrees hotter. So for a 180 thermostat, anything up to 200 would be normal.

[thematt]

The tech manual calls for 'Theromostat setting = 180F'. I was under the impression that anything above this means engine isn't being adequatly cooled. I always backed off before reaching 200, let alone high temp alarm state.


You're saying 200 might be normal at WOT??! Hell guys, it's knowledge gaps like these that kill me. If this is the case then coolings may not be an issue.


Alternator is different, but I measure rpm with IR sensor on the crank pully, and confirmed with a cool piece of kit called tiny tach.

[Wotname]

Originally Posted by rslifkin

Agreed, normal temp range is up to the thermostat fully open temp. However, the spec temp is usually the temp where it starts to open. Fully open is 15-20 degrees hotter. So for a 180 thermostat, anything up to 200 would be normal.

Yes, I wasn't clear enough. When I said it's 'design' temperature, I meant somewhat hotter than the marked opening temperature.

Originally Posted by thematt

The tech manual calls for 'Theromostat setting = 180F'. I was under the impression that anything above this means engine isn't being adequatly cooled. I always backed off before reaching 200, let alone high temp alarm state.


You're saying 200 might be normal at WOT??! Hell guys, it's knowledge gaps like these that kill me. If this is the case then coolings may not be an issue.
......

Which is why I suggested to pull the thermostat and actually measure it - heat in water and measure the temperature of the water when the thermostat is fully open. That should be max temperature for your engine cooling circuit.

As an aside, the oil circuit provides much of the cooling and usually reaches it max temperature after 30 or more minutes for any given load setting. Measure at the oil filter with an IR temp gun.