A Bugg's tale of Yamahas and hand grenades

[Spaniard_King]

Same as what goes in your Yammies mate

[Sandman]

Gary time to talk Bret into getting back to Honda . Bit of bad luck there Bret hope it turns around .

[Moonlighter]

Now your pushing my memory but we did a re-prop about 2 years ago. Managed to get them up to around 51-5200. They were 4800 before that.

And that there may be the root cause. Engines are over-propped. Lugging.

Garry, what is your opinion?

Mate of mine had a Yammy 250 HPDI on a boat he brought in from the States. Came with a big prop that wouldn't let the engine rev to is max rpm of 5500, it was lucky to get 4400. It had done only 120 hrs when he got it here. Immediately repropped it into the correct range. Despite that, only another 130 hrs later. ........ Bang! It was put down to the damage done early days before he got it.

[gofishin]

Sorry to hear of your woes bugs!

And that there may be the root cause. Engines are over-propped. Lugging...

It is weird how so many yank boats are propped like this eh Grant???

Those big V6 HPDI's were certainly YED's more often than not. A mate went through two quick smart, both went in less than double digit hours, one @ around 2hrs from memory. The majority of these were not propping issues though.
Cheers
Brendon


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[Darren Mc]

I don't know how much truth is in it but I was told by a selling dealer that the Yamaha hpdi's must be run in a very specific manner. He said that they allway's do the running in on the hpdi's they fit so they know it's done correctly.

[Noelm]

I don't know how much truth is in it but I was told by a selling dealer that the Yamaha hpdi's must be run in a very specific manner. He said that they allway's do the running in on the hpdi's they fit so they know it's done correctly.

Not a lot of truth in that.

[Moonlighter]

Sorry to hear of your woes bugs!

It is weird how so many yank boats are propped like this eh Grant???

Those big V6 HPDI's were certainly YED's more often than not. A mate went through two quick smart, both went in less than double digit hours, one @ around 2hrs from memory. The majority of these were not propping issues though.
Cheers
Brendon


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Agree, lots of US boats seem over propped.

Anyway, back to these F150's of Buggman's.

I wouldn't think that a stint propped at 4800 would have done them any good at all early on in their life, and I also doubt very much that a good Yammy dealer would be all that happy with them propped at 51-5200 either. Happy to stand corrected on that, of course.

[Dignity]

Bug an, how is your circumstance panning out, mine had the injectors cleaned and back in today and all is sweet again. I did ask about having the top cylinder not firing for about 3.5 hours but as the oil is drip fed into each cylinder the mechanic said it wasn't an issue, other motors where the oil is mixed prior to injection is a totally different issue. I also asked about not being able to get the WOT as per recommendation and he said the only real issue is that I wouldn't be getting all my horses and consequently the motor would be working harder and there is a possibility of the oil not getting everywhere it needs (can't remember the terminology he used but it does mention it in the manual) but if serviced regularly this also wasn't an issue.

I have almost no mechanical knowledge or ability and I am sure there are many urban myths around, I also have received differing opinions from different dealers and sometimes I wonder if they have any idea what they are talking about.

[bugman]

Agree, lots of US boats seem over propped.

Anyway, back to these F150's of Buggman's.

I wouldn't think that a stint propped at 4800 would have done them any good at all early on in their life, and I also doubt very much that a good Yammy dealer would be all that happy with them propped at 51-5200 either. Happy to stand corrected on that, of course.

Motors were fitted by Dolphin Marine on the Sunshine Coast - before I bought the boat - they'd done around 200 hours when I purchased it - mostly at troll or idle as it was used as a game boat. I re-propped it within 20-50 hours of purchase. The recommendations on props I used came from Solas. The original props were Solas as well.
Brett

[Moonlighter]

Hi Bugman
Not at all trying to cause grief here, just attempting to get some understanding of the situation and the possible cause. So please don't take offence, am not having a shot at you at all. i am sure you had those motors propped as was recommended to you.

In regards to props, it really isn't a matter of the make or manufacturer being right or wrong, it's what they do under power that matters. And to avoid lugging the engine, it is usually necessary to select a prop of a size (dia and pitch) that allows the engine to rev out to somewhere up near its max recommended rpm. That's not just my opinion, it's what the real experts who know this stuff intimately say.

The reality is that even if a prop is recommended for a particular boat/motor combo by a prop company, dealer or anyone else, it still needs to be tested and to do that you must run it to WOT (wide open throttle) to check that it gets into the expected rev range. It wouldn't be the first time, for example, that a prop that is supposed to be a 17 pitch is actually closer to 19. So, testing is really important.

I see that the current model Yammy F150 recommended rev range is 5000-6000, so, if your engines have the same recommendation, I expect the aim, if they are similar to other 4 strokes, would be to get the revs at WOT to at least 5500, probably closer to 58-5900 would be the go, with the boat carrying an average load when tested. As I mentioned earlier, I would be surprised if a Yammy dealer would allow a boat they set up to only achieve 5100rpm at WOT. I could be wrong, of course ,and maybe it is fine to prop a F150 like that. Would be very surprising, though.

My DF115 Suzuki 4 stroke is propped so that it gets 6100rpm at WOT. With an average load on board. My dealer told me to test it at WOT as soon as it was completed running in. When i reported back with those results he was pleased with that and confirmed the selected prop was a good choice.

Set like that my Zuke is not working hard or under load at the normal cruise speed of 42-4500 rpm, and also, propping them like that also usually gets the best economy too.

Conversely, propping them so that they get below the recommend rev range or at the lower end can be a bit like driving a car around in top gear all the time. Add a big load of gear and blokes, and it gets worse. Engine is under load constantly, and that reduces its life expectancy for all sorts of technical reasons that others can no doubt describe better than me. They all end, however, with a premature "bang!".

[AndrewB]

I had a Yamaha motor regularly serviced by Dolphin and no one else and traded it in on new one as it was old and starting to play up a bit. The dealer I bought the new motor off gave me a reasonable trade in deal subject to his mechanics going over the motor, they informed me that the motor had the overheating wire cut by someone so the overheating alarm would not sound. Other things came to light and now I use a mobile mechanic to do my servicing and I can see what he is doing and have confidence in his honesty and have no confidence or trust in marine shop mechanics doing the right thing.

[bonneville]

brilliant explanation moonlighter, from my perspective, that's 100% correct, especially when the motor is run in to check what maximum rev's are for that engine at wot, superb advice for purchasing a new outboard...
andrewb, heard many many similar stories as yours, having someone trusted servicing your engine if your unable to do yourself is important.
Having known and know many out board mechanic's, mobile and at large dealers, I don't know many that would cut a temp wire to push the problem under the carpet so to speak, but again I don't argue with your evidence either, but it would surely be detrimental if such practises did occur, for the mechanic and indeed the dealership. you've done the right thing if you had doubt, as long as the mobile guy was qualified, stamp the book etc and you can physically be there and literally annoy him with questions, then you've got a good result.


regards
bonneville

[bugman]

Gents,

I apologise - I said it was from memory and it would seem as if my memory wasn't that good - I've got a bit going on at the moment.
I've dug up my prop testing sheet:

Old prop:
WOT 5200 ... 27knots at 104.1lph (no trim)
WOT 5400 ... 30knots at 124lph (trimmed out)
New prop
WOT 5800 .. 29knots at 124lph (no trim)
WOT 6000 ... 31 knots at 128lph (trimmed out)

The initial props on the boat were not right - there's no doubt about that. Did it contribute to the detonation - time will tell.

Bett

[Dignity]

My F150 was purchased from Dolphin, not long before they lost their licence as a Yammy dealer, but the end result was they severely under propped boat how and why is pure conjecture, best at WOT was 4700 revs, fixed that with a Solas prop and got 5700 revs, better but at low revs developed a severe case of prop slap, since replaced the prop with a Yammy anti slap prop and hub, so much better.

I suspect that lots of trolling, as happens a lot with those chasing mackerel around my place where it takes 15 mins to get to the grounds and then spend the next 3 hrs trolling, is a possible cause due to the contamination of the oil requiring more frequent oil changing to resolve the problem. Other than this I can't find any reference why an under propped motor will cause it to go"Bang" as the motor will still be used at reasonable revs(unless lots of trolling involved) to avoid the above mentioned contamination, the motor is working harder and you aren't achieving the hp you paid for and therefore more wear and tear but the end result would be an innefficient, smokey, rattley motor.

I am not criticizing previous comments as I have mentioned that I am not mechanically minded but I try to read and understand what is being written and I still can't work out why the sudden "bang" theory is being promoted for an under propped motor.

[gofishin]

...New prop
WOT 5800 .. 29knots at 124lph (no trim)
WOT 6000 ... 31 knots at 128lph (trimmed out)...

That's makes a lot more sense Bugs!

Thought it was very strange that Garry was letting you run around at 5100 WOT with 'new props', even if there was yamahardness involved
Cheers


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