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patmvcr · 18-07-2019, 10:02

I couldn't find any thread about this...

I have owned my Hunter 466 (2003 model) since 2006. I'm still learning all the ins and outs of the powered aspect of a sailboat. I have the engine sort of figured out but have tended to neglect the shaft and prop aside from cleaning the barnacles off and keeping the anodes in working order.

I had the engine's injectors serviced 2 years ago (replaced 2 and cleaned the others) because the engine was running very smokey. At that time I was told to run the engine at higher RPM's to keep it happy... I had been running it at about 2500-3000 RPM thinking that was ideal. So I ran it at max throttle (3100 RPM).

I recently hauled out the boat to bottom coat and was told by the mechanic who replaced the cutlass bearing (different from the guys who serviced the engine 2 years ago) after doing his sea trial that my propeller is likely "over-pitched" as the engine (Yanmar 4JH3-TE) with a Kanzaki KM4A transmission (gear ratio 2.63) is not running at the right RPM at full throttle - should be 3900 RPM and the most I can get is about 3100 RPM. Of course he told me this AFTER we were back in the water. I explained that the prop was set at the same pitch as when I got the boat and assumed it was correct. He said that sailboat owners tend to over-pitch their props thinking they are saving fuel running at lower RPMs (as I was doing), but in fact are just wasting fuel out the exhaust (something to do with the turbo charging). I decided to look into this.

My prop is a MaxProp 3 Blade fast (V.P.). I scared up the original operator's manual and found that the PO had set the pitch at 25 degrees, which for my 18" 3 blade prop corresponds to a pitch of about 14" based on their table. I noticed from the PO's notes that he used the wrong gear ratio for the calculation (he used 2.83 rather than 2.63).

From the vicprop.com site I calculated that for my hull shape (LOA 40', beam 14' and draft excluding keel of 3') and displacement (27,000 lbs) , engine power rating of 75 HP that my 18" prop should be set at about 22" for a desired hull speed of 8.5 knots.

On the weekend I went down with my mask on to check the prop's setting and sure enough it was set at 25 degrees (RIGHT). I tried to reset the pitch... easy enough to do with that prop model if the mechanicals of the pitch adjustment collar weren't gummed up.. but could only manage to slip the collar up but not adjust anything... so I just had to leave it as is.

So my question to the audience is this: How worried should I be about this? Should I be hauling out and cleaning up the prop and adjusting it to 22 degrees, or do I just live with it until I haul again in 2 years time (haul out is about $800). And If I live with it as is for now, should I be lowering my engine RPM.. as I right now tend to run it a full throttle (3100 RPM). Am I damaging the engine running it at 3100 RPM? Note that it doesn't overheat or sound weird.

Thanks for any input..

Jammer · 18-07-2019, 14:11

Welcome to the forums.

How much do you motor?

deblen · 18-07-2019, 15:10

If your engine is reaching 3100 RPM @ wide open throttle while powering along,I don't think you are pitched too heavy-(maybe just a hair).
What GPS speed over bottom (with no current) do you reach @ 3100RPM?
" " " " " " " " " @ 2600 RPM?

24-2600RPM would be near optimum cruising RPM for you IMHO. / Len

psk125 · 18-07-2019, 17:55

It sounds like the prop has been like this since 2003 and hasn't caused any real problems. Maybe you are burning more fuel than you have to, but your fuel bill isn't going to change much from previous years, and you've obviously been able to live with that. Fix it when it is convenient the next time you haul, or have a diver do the adjustment underwater if it worries you. If the mechanic had thought it THAT important, he would have told you before you splashed.

**roverhi** · 18-07-2019, 19:01

We cruised for over 2 years and owned the boat for 10 years with an over pitched propellor, can't remember the details but we were several hundred rpm below what it should have been max rpm. We were careful not to run the engine up to the point where it began smoking. Seem to remember a 3,000 rpm redline and we never ran higher than 2500 rpm and mostly closer to 2000 rpm. The new owners of the boat put a new proper size/pitch prop on it. Boat made 3 trips to SoPac and more than 20 years with the original engine.

Don't lug the engine, throttle back a 100 or so rpm when it starts smoking and I'd probably set it back a couple hundred rpm. Wouldn't panic but wait it's convenient to repitch the prop. If you want to change the pitch soon most yards will hang a boat for you to do it for a reduced fee if it's only an hour or so.

Compass790 · 18-07-2019, 19:24

Well if it doesn't overheat & sound weird I wouldnt sweat it too much till next haulout but I don't know much about turbos.
max revs continuous are 3700 for that engine, 1 hr rating is 3800 FYI
Aren't there any tidal grids or seawall you can let it dry out at & then adjust pitch?
Our tiny Yanmar ysm8 is badly overpropped, max revs is 2400 in gear with a clean bottom & max revs is 3400 in neutral & it doesn't seem to care though I do & will fix it eventually. We just make sure we dont push it up to the point it's blowing black smoke.
Better you get advice from turbo people.

patmvcr · 18-07-2019, 23:36

OK

Thanks for the input..

First off, we do motor quite a bit.. seems we always have a headwind heading out and headwind heading home... and never have enough time to tack... so yes we motor quite a bit.

The engine doesn't smoke now after the injectors were sorted out.. but i wonder if that was the root of the problem running it at low RPM and over pitched. Maybe we will just keep it a couple of hundred RPM below the max and will adjust the prop next haul out.

**GordMay** · 19-07-2019, 02:28

Greetings and welcome aboard the CF, patmvcr.
The 4JH3-TE seems to be rated 3700 continuous / 3800 maximum RPM ➥ https://www.simplicity-marine.com/pdf/Yanmar/JH.pdf
See also ➥ http://www.cruisersforum.com/forums/...ms-158075.html

Compass790 · 19-07-2019, 19:11

Quote:

Originally Posted by patmvcr

OK

Thanks for the input..

First off, we do motor quite a bit.. seems we always have a headwind heading out and headwind heading home... and never have enough time to tack... so yes we motor quite a bit.

The engine doesn't smoke now after the injectors were sorted out.. but i wonder if that was the root of the problem running it at low RPM and over pitched. Maybe we will just keep it a couple of hundred RPM below the max and will adjust the prop next haul out.

How many hours on the engine? Maybe the injectors just got dirty or worn with time, they don't last forever. Best thing you can do to help injectors AFAIK is feed them clean dry fuel. But yes you need feedback from another 4jh3-te owner
Leaving it to next haulout doesn't sound too bad to me but some engine manufacturers wont honour the warranty if you are over-propped. Good idea to be a couple of hundred rpm below max as you said you would do probably. If the coolant temp & oil pressure & temp is ok you can't be overloading it too badly.
The problem for us being overpropped is we cant get to max hp in the rev range so we get drastically slowed in a headwind & sea but I'm guessing you still have adequate power with that size engine.

kenbo · 19-07-2019, 19:55

When you're over propped watching the coolant temperature is not the best indication of high engine temps, exhaust gas temperature is what matters. If your tach is calibrated and accurate, you're 600 to 700 rpm to low. Each inch of pitch is about 200-225 rpm so empirically you need to reduce your pitch by 3".

Does over propping an engine shorten it's life, yes. Will you have problems within the 2 years before haulout, that's your call.

Compass790 · 19-07-2019, 21:09

Just noticed in post #1 OP is confusing degrees with inches of pitch. When vic prop calc says your pitch should be 22" thats not 22 degrees . It means in one rotation of the prop it drives the boat forward 22" ( assuming no slippage). Is your max prop marked in degrees or inches of pitch? I'd assume inches of pitch.
No argument with kenbo saying EGT is better load indicator but doubt OP has one. Also note the boat has been going since 2003 overpropped so it's unlikely to die in the next 2 years

CassidyNZ · 19-07-2019, 21:52

To the OP, FYI, I have just been closely involved with a repower in which the same engine you have (may be a later derivative, it’s a 16 valve, brand new) was fitted to a boat by the local authorised Yanmar agent. The boat is a Roberts 43 running on a Borg Warner Velvet Drive transmission, I don’t recall the ratios. But all that is actually irrelevant.

What I wanted to say is that agents who installed the engine had to conform to Yanmar’s requirements when the installation was commissioned.

Their requirement was the engine reached 3200rpm, wide open throttle and an exhaust back pressure of less than 2.8. After repitching the prop the boat achieved both and was signed off and the warranty issued.

So anyone saying that the engine must reach more than that should check with a Yanmar.

Wotname · 20-07-2019, 00:47

Quote:

Originally Posted by CassidyNZ

To the OP, FYI, I have just been closely involved with a repower in which the same engine you have (may be a later derivative, it’s a 16 valve, brand new) was fitted to a boat by the local authorised Yanmar agent. The boat is a Roberts 43 running on a Borg Warner Velvet Drive transmission, I don’t recall the ratios. But all that is actually irrelevant.

What I wanted to say is that agents who installed the engine had to conform to Yanmar’s requirements when the installation was commissioned.

Their requirement was the engine reached 3200rpm, wide open throttle and an exhaust back pressure of less than 2.8. After repitching the prop the boat achieved both and was signed off and the warranty issued.

So anyone saying that the engine must reach more than that should check with a Yanmar.

Curious!
Was the rpm of 3200 a minimum or maximum? I'm assuming it was a minimum as it seems unlikely that Yanmar would want to prevent one from reaching max continuous rated rpm if one so chose to do so.

kenbo · 20-07-2019, 02:16

Quote:

Originally Posted by CassidyNZ

To the OP, FYI, I have just been closely involved with a repower in which the same engine you have (may be a later derivative, it’s a 16 valve, brand new) was fitted to a boat by the local authorised Yanmar agent. The boat is a Roberts 43 running on a Borg Warner Velvet Drive transmission, I don’t recall the ratios. But all that is actually irrelevant.

What I wanted to say is that agents who installed the engine had to conform to Yanmar’s requirements when the installation was commissioned.

Their requirement was the engine reached 3200rpm, wide open throttle and an exhaust back pressure of less than 2.8. After repitching the prop the boat achieved both and was signed off and the warranty issued.

So anyone saying that the engine must reach more than that should check with a Yanmar.

Not doubting your story at all but a fact that you're missing is that the OP's engine is 4JH3. This engine has the highest Target rpm in the JH series, 3800. The next in the series, the 4JH4, the target is 3200. The devil is in the details.