Topic: Gannet 4stroke ic marine 15cc engine (Read 18118 times)

Dave J · « **on:** April 20, 2014, 03:53:15 pm »

I have been running the IC Gannet engine in a launch but I have been unable to obtain any information on a the engine settings. The boat only runs for a couple of minutes and then shuts down.
The engine has a seperate Amal float chamber.
Where should the float chamber be in relation to the carb? At the moment it is below the carb.
Should the main fuel tank be above the carb?
How often does the oil container on the front of the engine crankcase need to be filled?
The engine and boat are at least 40 years old.

BrianB6 · « **Reply #1 on:** April 21, 2014, 08:44:46 am »

Top of fuel level (tank or float chamber) should be 1/2" 12 mm. below Jet level of Carby.
The motor should be able to suck up the fuel from about 2" below the Jet level so the position is not that critical but the closer the level to 1/2" the better.
If you are using a float chamber, the lowest level in the tank should be above the float chamber so that it can drain in by gravity.
Attachment is from N & M's Instruction manual.
Almost full manual avalailable if you P.M. me. Unfortunatly it has been sitting in a damp shed for several years and the first 2 and last pages are almost unreadable.

Dave J · « **Reply #2 on:** April 21, 2014, 09:28:22 pm »

Thank you for the reply, When I got the Launch the Float chamber was loose I had positioned it back in its original position, but was unsure why it had been taken off. The original position was about 1/2" below the carb inlet which corresponds to your N & M Instruction manual.(Is this manual a Gannet Instruction Manual?) I had found Engine description information sheets but nothing about the setting up running instructions. The needle valve is about 1/4 of a turn open and I need to keep the revs up when I put it into the water, when I try to adjust the tick over it stalls, I don't seem able to get the balance correct.

BrianB6 · « **Reply #3 on:** April 21, 2014, 11:43:06 pm »

N&M are Nurthen and Muirhead, the two engineers who built the engines. My father bought ours directly from them.
There should be a line scribed on the top of the needle valve which was the original mark put on after they set up each engine. Not more than 1 turn open and not more than 25 degrees either way from the mark.
The starting ignition setting is with the lever vertical but may need to be slightly advanced for running under load. The position can only be found by experience.
Oil is sufficient for about 10 - 15 minutes running.
In the old days one needed to add upper cylinder lubricant (Reddex) to the mix but it is unavailable now. Remember it was designed for leaded fuel so may need premium petrol now.

BrianB6 · « **Reply #4 on:** April 21, 2014, 11:54:47 pm »

Hi Dave
I would be interested to see a picture of your boat.
My father built a couple including Tuk Tuk, named after the sounds our baby daughter made!
I still have the hull with the engine but the rest seems to have gone unfortunatly.

Dave J · « **Reply #5 on:** April 22, 2014, 04:26:07 pm »

Hello Brian, Thank you for the information you have posted, the diagrams and the photograph have given me new leads in sorting the engine out. For example I noticed on your photograph that the fuel tank is forward of the engine, at present my tank is towards the stern, also I have not moved the Advance/retard lever. I have managed to get "reddex" for the fuel. Your hull looks very similar to mine in size and shape.

BrianB6 · « **Reply #6 on:** April 23, 2014, 12:01:06 am »

Any chance of a photo?
Dad had an earlier boat that was very similar although I think he broke it up after he built TukTuk.
I designed both of them although he built them.
The size and shape were popular for Gannets in the 1960's and were pretty seaworthy.

Dave J · « **Reply #7 on:** April 24, 2014, 10:55:44 am »

photo showing Gannet engine in the hull

BrianB6 · « **Reply #8 on:** April 24, 2014, 11:10:52 am »

Thanks for the photo.
Just a couple of points:
The float chamber looks much to high above the carby.
The fuel supply pipe appears far to long and could be causing a restriction in the flow.

Bill D203 · « **Reply #9 on:** April 24, 2014, 05:06:45 pm »

What a lovely engine. fantastic to see it , dose it still run?

Dave J · « **Reply #10 on:** April 25, 2014, 07:24:37 pm »

Brian,
The float chamber was loose and could have caused previous problems. I could remove the float chamber and position the tank nearer to the engine in line with your diagram. Would there be any advantage in linking the advance/retard lever to a servo? as well

BrianB6 · « **Reply #11 on:** April 26, 2014, 12:08:27 am »

Dave
I would keep the float tank if you can and move the tank closer. The float tank keeps the fuel volume steady eliminating the varying fuel level problem with just a tank.
Connecting a servo to the lever is a good idea but it would have to be a very slow moving one since it does not take much movement to alter the setting.
We used to adjust it with the boat held between our legs or by another person, when running at full throttle in the water. Once the correct position is found it should not vary much between running sessions.
I ought to look at reviving Dads boat but where to run it is a problem over here as many waters prohibit I.C. power because of pollution and noise although the Gannet is pretty quiet if properly silenced. Thoughtless few spoil it for the many!

sparkey · « **Reply #12 on:** April 26, 2014, 09:23:24 am »

I had a Gannet in a air sea rescue launch in 1965 which I bought from hobbies in Camdem town (Ithink they are still there),can't remember how much it cost but it was a hell of a lot, sold my motorbike to pay for it a BSA c15 250cc,the Gannet great motor with few vices but the cost put people off,as long as you look after it, it will not let you down,lubrication is important check oil and rockers,other than that I can't add to what has already been said,Ray.

Dave J · « **Reply #13 on:** May 17, 2014, 08:24:29 pm »

Brian, I have also been looking at the prop, it is 2.5 inch dia two bladed, may be should be smaller diameter? see attached photo.

BrianB6 · « **Reply #14 on:** May 18, 2014, 06:59:54 am »

Recommended size was 2 3/4" to 3" x 3" pitch. 2 or 3 blades.
We used 2 1/2" dia. not sure of the pitch. 3 blade as the 3 blades gave slightly smoother running.
N & M made props specifically for their Gannet and as far as I know ours is one of them.

Dave J · « **Reply #15 on:** May 21, 2014, 09:19:40 pm »

Brian, Thank for the information on the prop size, I was surprised at the 3" dia reference.
I have attached a photo of the boat which is 36.5" long, 13" beam and has a side hull height of 5". The hull and top cabin are made from fibre glass (possible 1960's model kit). The model is based on the full size Vosper PL4 80ft service launch which was constructed for the Shell Company to be used on Lake Maracaibo in Venezuela and would carry up to 60 passengers with a speed of 35 knots.

BrianB6 · « **Reply #16 on:** May 25, 2014, 07:40:42 am »

Hi Dave
I tend to agree with you that 3" is probably on the big side.
If you can get the proper 3 blade 2 1/2" Gannet prop that would be best. Just check yours, some of them had gan stamped on the boss.
The original PL4 was 46" long and yours might be a bit small for the Gannet. Most boats that they were installed in were about 42" to 48"

Dave J · « **Reply #17 on:** June 04, 2014, 08:45:37 pm »

Brian, I have taken the propeller off, cleaned it up, it has been made from stainless material and does not have any identification marks on it. I noted the faricated hull on the Vic Smeed hull only has a 9.5 inch beam, this hull is 13 inches and has plenty of free space. I have now re-sited the tank nearer the engine, taken off the float chamber, put a filter in line and also fitted a starting belt (which in my case has improved the starting proceedure)
See attached photo, the centre of the hull is very black/discoloured, could have been a tank or batteries?

Dave J · « **Reply #18 on:** June 11, 2014, 11:29:50 pm »

I decided to insulate the exhaust pipe with heat resistant bandage and removed the pipe off the engine. I then noticed the carbon hard deposit in the exhaust port of the cylinder head, which reduced the bore by 50%. I have now taken the head off and removed the valves the seats looked alright but the carbon deposit was evident in the outlet port. See attached photograph. I have now removed this deposit and lightly reground the valves in, reassembled the engine. The exhaust pipe and expansion chamber although lined with a deposite of carbon being a larger bore did not restrict the exhaust.This deposit could not be removed easily and was re- assembled on the engine. The engine has now been test run out of the water and the improvement in the performance is 100% with a tick over being achieved and continual running not a problem.

craig dickson · « **Reply #19 on:** June 14, 2014, 05:51:40 pm »

I have to say guys, this is a fascinating topic and the photos are a delight to see!

Thank you all for sharing them on here

Craig

spearfish99 · « **Reply #20 on:** June 14, 2014, 08:28:53 pm »

Hi Dave,
I have a Gannet with a magneto in a 48"Screwdriver offshore racer built in the mid 1970's. Hasn't run for a few years but kept oiled up and got out to be admired every so often, I'm sure you know what I mean. I bought two genuine Gannet props off of Nurthen just before they closed, having the engine checked over at the same time . They are large, made of brass and very basic looking. They didn't drive the hull very well , we used a red plastic X70 initially , then a large metal racing prop for most running which was quite impressive. You are welcome to the props if I can find them. Drop me a PM if you would like them. Incidentally, I had exactly the same problem with valve carbonisation after running for some time. After cleaning valves, used to add a tiny drop of Redex to fuel mix to try an avoid in the future
I will try and attach a few pics of the Screwdriver if I can get them to load

BrianB6 · « **Reply #21 on:** June 15, 2014, 12:59:22 am »

Hi Dave
I should have thought of it needing a 'decoke'. We had to do ours a couple of times.
Your prop, if it is stainless steel, could be a Taplin, brought out originally for the 7 cc. Taplin Twin diesel. They were a 'cheap' alternative if you could not get a Gannet one.
PM sent.

Dave J · « **Reply #22 on:** June 16, 2014, 10:45:56 am »

Thank you for the photographs of the Spearfish, on 0038 to 0039 shots you have a container in a spring clip attached to the crank case between the push rods, is this a sealed unit? my engine only has a open outlet. I have changed the prop to plastic 50mm, which ran but lacked performance I have now replaced that one with a metal 2222 25 prop (50mm) which has made a difference. I am going to renew the condenser on the points, which could be affecting the ignition. Could you tell me how many turns the screw is open in the crankcase oil cylinder?, mine was 4 turns

spearfish99 · « **Reply #23 on:** June 16, 2014, 12:27:08 pm »

Hi Dave,
The container you mention in the clip is actually a catch tank for the oil which comes out of the crankcase outlet/vent. It is simply an Ilford metal 35mm film container . It has an inlet and a tiny breather hole drilled in its top. It isn't strictly necessary, but just stops the "goop" being thrown everywhere and needing cleaning out of the boat. On my engine , the oil was considerably thinned by the petrol going through the engine and was messy. I am not sure how many turns on the oil container valve, but I used to reckon on 15 minutes maximum run on the water with a tiny drop of oil left in the container. If not sure, err on the generous side, running out of oil on the water would not be good.
I think that at 50mm your prop is still a bit small. The joy of the Gannet is not its revs , but the torque that it produces.The Screwdriver was probably not as fast with the Gannet as it would have been with a 10cc glow of its day (which it was originally designed for) but it planed very nicely and nothing stopped it , ( weed waves etc!). Might be worth trying something a bit bigger to see if you can extract the full power from the engine while keeping the revs down a bit.

Dave J · « **Reply #24 on:** June 17, 2014, 08:07:52 pm »

Thank you for the information about the oil container, I was thinking the open hole might have been a form of crankcase breather. I have now replaced the condenser and reset the points. The engine appears to start easier. On initial runs the hull ran with bow down with the water breaking over the bow, I put 3lb of lead in the stern and it has levelled the hull to a more realistic angle. The boat has a total weight of 20lb (8.75 Kilo). I have ran the boat with the X50 size prop and it sailed for a 5 minute run with no ignition problems. See attached photographs.
The 70mm prop could improve the performance and also adjusting the advance and retard settings could change the performance, thank you all for the advice.

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Author Topic: Gannet 4stroke ic marine 15cc engine (Read 18118 times)