Any Yanmar 4LHA - STP (or most mechanical diesel) Gurus out there?

wofforduk

wofforduk

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Hi All

After a great and successful season boating under diesel power, I have a bit of a question, that id like to confirm!

I posted back in July about the engine i have used - have a look - hope this link works

First off - I know ill be asked these questions so ill say now, that the engine is happy. Its not blowing black some, noises ect.

My small niggle is that (once warm) it wont rev up past 2.8k in neutral. I bought this from a commercial boat, so I presume they have restricted this for longevity ect. under full load she achieves around 2.6-2.7 rpm so I dont think its a prop issue.

My reason for asking is because looking at the prop horsepower graph, if the previous mechanic has restricted her to 2.8, i would be loosing around 100hp. Im not someone to go around at 100% throttle all the time, but it would be nice to get the most out of it when needed.

So I presume this is a case of let her warm up, and gently unwind the max fuel screw until I reach 3.4k in neutral?

Will be buying a separate tacho to confirm the speed, as ever wary of the in dash one.!!

perfcv230.jpg


Shows the curve and why Id like to push it just a little bit. Video of the boat going is here to show its condition - 28knts WOT at the mo, i recon i could get 35knts with the extra 100hp!


Cheers
Will
 
The fuel screw alone won't up the revs the engine will be rev limited elsewhere maybe as simple as the throttle stop screw screwed in but possibly had the pump governor tweaked by a fuel shop
Pumps are a bit of a 'dark art' so probably best to find a pump expert who is familiar with the model of pump
I have the 4lh manual at home but I'm away till next week I'll have a look when I'm home see if it offers any clues if no one else has answered the question
 
Thanks Ken, ill keep looking. IM under the assumption the Governor in the pump will be pre set and not adjustable? its a bit of a tricky one haha!
 
The governor may be adjustable but it will be a specialist job.
If iirc the 4lh has two adjusting screws on the top of the pump one sets max throttle travel the other idle position it may be as simple as adjusting the screw that sets max deflection on the throttle lever
It may be worth googling the pump model no & seeing if there is any info online
 
Your throttle lever sets RPM the governor then adjusts the fuel delivery to achieve that RPM
.
As you have the situation that you can set the RPM to 2,900 in gear but only achieve 2,700 2,800 that means the engine will be getting getting full fuel, producing maximum power at that RPM but not quite getting to the throttle RPM.

You can increase the fuel setting but that usually means black smoke. In fact in old days that adjustment was actually known as the smoke stop. By overfueling a diesel you can get 20 to 30 % extra BHP but at the cost of considerable smoke. When I demonstrated this on the dyno I made sure there was no wash hanging out locally beforehand.

I would leave it alone.
 
I knew I'd get someone to say leave it, and yes, if it ain't broke not fix it. But I didn't know this would be limited when I bought her, and if I wanted a 120hp engine in the first place it probably would have saved me a lot of money! :D

Hence my reason for thinking about tuning her up back to what she should be. I'm not after getting more out than what it's designed to do.

Cheers will
 
So I presume this is a case of let her warm up, and gently unwind the max fuel screw until I reach 3.4k in neutral?
Click to expand...

Sure you can do this.

You will get 3.4k in neutral.

In gear you will get exactly the RPM you had before. 2.6 to 2.7k

If you want those extra horses you need to alter the prop reducing either the diameter or the pitch. This will come at the expense of higher fuel consumption.
 
Well, it's been a busy day here at Mets, but i did have a main agent for Yanmar on my stand so thought id ask him. They restricted this engine just by the max fuel setting, something which he personally has done, for commercial application. After hearing what I have said to him, he confirmed my gearing was spot on, and yes, just undo the fuel bolt till I reached 3.3k in neutral, and it will be back to normal :) from the horses mouth hey ;) just need to get the boat back in water and give it a go :)

Cheers
Will
 
Not a bad idea, and could probably do it in a testing tank rather than in water! I'll get in winding hopefully at the weekend. No reason really why not to use the power I bought I guess!! :)

Cheers
Will
 
I just had a chance to look at the manual & it is as the dealer says one of the adjusting bolts at the top of the pump it basically limits how far the leaver can move
it also looks like you can adjust the internal centrifugal governor but id try the limit stops first

if you pm me your email address I may be able to email you the manual for further reference if I cant send the complete manual i'll send you the relevant pages that refer to the pump

ken
 
wofforduk said:
Well, it's been a busy day here at Mets, but i did have a main agent for Yanmar on my stand so thought id ask him. They restricted this engine just by the max fuel setting, something which he personally has done, for commercial application. After hearing what I have said to him, he confirmed my gearing was spot on, and yes, just undo the fuel bolt till I reached 3.3k in neutral, and it will be back to normal :) from the horses mouth hey ;) just need to get the boat back in water and give it a go :)

Cheers
Will
Click to expand...

Well you have it from the man on the stand.

However I strongly suspect that in gear it will behave as before and max out at 2.6 2.7 k.

On every injector pump and governor I have ever worked on and there has been a few adjusting the maximum fuel stop would have no effect on max RPM.
 
wofforduk said:
Not a bad idea, and could probably do it in a testing tank rather than in water! I'll get in winding hopefully at the weekend. No reason really why not to use the power I bought I guess!! :)

Cheers
Will
Click to expand...

Will

You are cruzin for a bruzin the guy on the Barrus stand was completely wrong.

Rob is on the correct track, however you must perform high idle test in the water not in a tank whatever that means exactly.

Number 1 Yanmar tachometer's are notorious for over reading by anything up to 200 rpm, use optical tacho and calibrate, dill switch setting of 127 comes to mind for this engine.

High idle you must make 3,686 +- 25 rpm out on the droop with tacho calibrated.

This engine needs to be propped to achieve between 3,425/3,525 clean.

Brilliant engine however has the life of a disposable cigarette lighter if you get it wrong.

US Yanmar distributors get it, the distributor you spoke to obviously does not.

PM me and I will send you the document.
 
TQA said:
Well you have it from the man on the stand.

However I strongly suspect that in gear it will behave as before and max out at 2.6 2.7 k.

On every injector pump and governor I have ever worked on and there has been a few adjusting the maximum fuel stop would have no effect on max RPM.
Click to expand...

I have just reread what I posted and it is of course WRONG. I must have been too tired to think straight.

What I meant to say was that you have been told to adjust the maximum RPM stop on the governor. So will rev higher IF it has the power to drive the prop at a higher speed.

Power is controlled by the fuel delivery to the injectors. I do not believe you have changed that so you will still be reaching the same 2.6 to 2.7 k.
 
Okay so sorry to pull an old old thread, but more for information with anyone else with same issues - i have found a bit of info. Over last weekend I have tested the boat in a lake doing the pre season checks and bought a laser tacho that is accurate to .1 RPM up to 10000 or something silly so yeah, its accurate. the engine Tacho guage is WELL OFF.... I set the engine to tacho of 1.5k, the laser was saying the engine was at 2k... thats 500rpm off! As i didnt have any help i didnt manage to take it to WOT and see what it was doing, but happy knowing that the engine is giving what its meant to, and wont start touching it! Just wonder if theres a calibration pot on the tacho so its showing correctly... one way to find out!


Bring on some warm days! :)
 
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