Dolphin engine rant

black mercury said:
It could be worn seals on the crankshaft, drawing in air when warm, or the roller bearings could be shot causing too much movement around the seals. They are easy to dismantle, undo head bolts, lift off flat head, then undo bolts securing the cylinder block. Lift block up leaving the pistons behind. You can then turn engine over using the pistons to feel for any roughness, should be nice and smooth. p.s. the crankshaft is pressed together so its either a return to dolphin job or specialist in two strokes.
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+1
We have had this problem with marine two-strokes. Stuarts were particularly susceptible to the point that they would peter out and stop when hot, accompanied by a lot of spitting back through the carb. The solution was to fit proper lip seals to the crank journals in place of the original bronze ring seals.
 
Dolphins very rarely suffer fron leaking crankcase seals, I fitted one to an Anderson 22 & it was a great success, like having a small turbine under the deck, max hull speed coincided with about half throttle & max fuel ecomomy. Quiet & smooth & less drag than an outboard in a well.
 
Robin said:
Stuart Turners were very often problems because of clogged exhausts. I once helped a friend with one in a Macwester 26, 'cook' his exhaust on a beach bonfire in Christchurch to try and burn off the baked in carbon. It worked to an extent but he later took the exhaust piping to work where he was an engineer and had it caustic bath cleaned after which the engine ran just fine. I do also recall with that engine only one type of champion spark plug would work properly too.
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Now THAT is very interesting...when I bought the boat it had champion n5 plugs which when I decided to change them I couldn't get quick enough so I bought Bosch equivelant!! Whether I am convincing myself or not I'm not sure but I have a feeling this latest lack of power has only happened since changing the plugs. I have also been using the cheap oil because its at the nearest garage to the boat! Hmmm I need to get back to the boat...I will try plugs and let you know after the weekend. Thanks for the ray of hope Robin.
 
johnalison said:
I had a Dolphin years ago and my main memory of its workings is that it mattered a great deal which plugs you used. Maybe modern versions and modern plugs have changed, but it might be worth seeing if a better plug would help. Good quality oil also affected its use.
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Two replies with same suggestion! That's got to be worth trying and as replied to Robin I have different plugs and oil than when I bought it, so it could be human error and my lovely Dolphin is blameless.
 
Dougy said:
Two replies with same suggestion! That's got to be worth trying and as replied to Robin I have different plugs and oil than when I bought it, so it could be human error and my lovely Dolphin is blameless.
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I know on the Stuart, my friend back then re made the ignition system in the end and replaced the original magneto with a modern electronic device/coil and he tried endless plug grade, variants all from champion ,before finding the right combination and I' not sure that even then he may have had a different grade on one cylinder than the other. Sadly he is long dead and I can't ask him (yet!)

I very nearly bought a Hustler 30 once with a Dolphin, but the owner had a lst minute change of mind because they put the price of his 'new boat' up and so he kept it. I bought a Liz 30 with a 10 hp bukh instead., both lovely boats however.

Good luck.
 
:) WELL Would you adam n eve it????? I couldn't wait so knocked off early and went to boat with my clutched straws in hand, oh and my 2hp outboard handle snapped on the way!!! minor problem lol... Anyway I sat and stared at the Dolphin mounted on my seal, something you don't see very often, and retraced all the things that went wrong since buying it,,,,with the engine, the boat itself is great, apart from the keel leeks a tad and its very weedy but I digress.... I tried to be logical, methodical and a couple of other icals and remembered when i bought it it ran sweet as a nut, so I have replaced the old cleaned up Champion n-5 plugs and it went bang!! No it worked!!!!!!!!! fanfare and fireworks required and a big thank you Robin and Mr Jonalison for the simple and to be honest most untecky suggestion of them all lol..I would never have thought brand new plugs that were sparking perfect out the engine wouldnt run properly in. I have looked closely at the plugs and they are different! The core in the middle of the champion is smaller than the boasch, different diameter and the very bottom bit that the spark jumps to (tecky talk) is wider on the Bosch than the champion...so thank you all for the input. Im off to watch the Bournemouth airshow tomorrow from the sea, it will be me whizzing around under motor showing off my seal mounted by a dolphin...I have attached pics if it worked.. Thanks again all....IMG_20150821_151947022_HDR[1].jpgIMG_20150821_152138218_HDR[1].jpg
 
Dougy said:
I would never have thought brand new plugs that were sparking perfect out the engine wouldnt run properly in. I have looked closely at the plugs and they are different! The core in the middle of the champion is smaller than the boasch, different diameter and the very bottom bit that the spark jumps to (tecky talk) is wider on the Bosch than the champion...so thank you all for the input. Im off to watch the Bournemouth airshow tomorrow from the sea, it will be me whizzing around under motor showing off my seal mounted by a dolphin...I have attached pics if it worked.. Thanks again all....View attachment 53209View attachment 53210
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From that picture it looks as if the Bosch plugs were too small to engage with the threads ... I presume it was leaking like fury round them.
 
JumbleDuck said:
From that picture it looks as if the Bosch plugs were too small to engage with the threads ... I presume it was leaking like fury round them.
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I have, sorry had, no idea it could make so much difference, and your comments make sense also as each time I took a Bosch plug out I did notice the thread was oiled up as well and thought strange but took no notice..I searched web for Champion but it just offered alternatives so I need to find a supply of Champion n5 plugs..on the net now doing exactly that. Then off to boat to motor, stuff the sails now lol.
 
I now have to open a new topic...Where can you find original champion n5 spark plugs all I can find is n5c which has a copper core and not sure if this will make a difference..it goes on...
 
N5 might be found at a lawnmower shop or they are the old fitment for original BMC minis'.
The C for copper shouldn't matter..
Good luck
 
black mercury said:
My dolphin came from factory with NGK BP5ES plugs fitted, but it had electronic ignition, so could be different from the points set up that you have.
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In NGK-land the "5" is the heat rating. A 5 runs a bit hotter than a 6. I have a distant recollection that Champion's standard rating falls between an NGK 5 and 6, so it may well be that either is fine. I'd probably go for hotter on a two stroke.

Useful stuff at http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp, including

chartheatratingflowpath-2.gif
 
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