The 5R was one of the very last motors that ‘Chillington’ developed in 1992 & 93. It had a slightly thicker crankshaft (17mm), with three deep ball bearings, one at the bottom and two at the top. A roller big end was also fitted. The sealing of the crank was made with two 17mm x 35mm oil seals.
The block had the exhaust flange removed, and the unit sat on a Yamaha leg with 360 degree pivot and normally a FNR gearbox. There was an adapter plate made from a machined block of aluminum, fitted with a Yamaha twist grip tiller arm. The adapter plate had the engine number stamped into it; see below.
The leg allowed pivot reverse, but there was a model with FNR gears.
Engine Numbers were apparently prefixed ‘SK’. The ‘L’ was used for long shaft versions, and ‘R’ was added to all those with roller bearings. From this I deduce that some were plain bearing, probably Kingfisher cranks. (With or without roller big end?) The ‘R’ in the model ID related to the ‘Remote Tank’ option, which was fitted to all soon after production started.
I have only come across one of these units intact. I can’t find out how many they made, but there were not many. The failure of the crankshaft and its bearings, from the evidence of the scrap ones I have seen, could be the reason.
The 5R is sought after by those who race seagulls, as the most ‘tweakable’ seagull. Have a look at the ‘propspring’ or ‘New Zealand’ web sites on the links page.
Some parts are available. I am indebted to Charles Large for filling in some of the gaps in the technical details.
This article by Charles was added to the Forum in 2008, following a 5R being offered on that auction site... it was felt it might be an idea to print it again here, good idea too, so here it is!
Now I feel I should give a little history on this
motor series.
In the early 90’s Seagull were in competition with mainly Japanese
manufactures who were turning out 5hp outboards, that were running on a 50
or a 100 : 1 oil mix, at this time the best Seagull could run on was 25 :
1 in the QB series, after fitting the needle roller crankshaft in the
Kingfisher they upped the fuel ratio to 50 : 1 to try & keep up.
Only to discover that many of these motors were not lasting the first year
before suffering lube problems on the main bearings, often requiring a new
crankcase, a very expensive warranty claim for what was now a small
English manufacturer.
So they decided to follow the Japanese example, & move to a fully bearing
crankshaft this coincided with the FNR gear box availability problem, so
they looked at buying complete legs first from Selva & then from Yamaha,
the decision was taken to follow the Yamaha route & a leg from the 4B
single cylinder 4hp outboard was chosen, probably on the grounds of cost,
as the Selva would appear more useful for Seagull traditional user base,
with it’s lower gear ratio, larger prop & it’s through the prop exhaust,
giving a quieter engine more suitable to the larger hull.
To attach the Yamaha leg to the Kingfisher power head an adapter plate was
designed, a complicated heavy aluminium casting that solved the problem of
delivering the exhaust gases to where the leg needed them & the cooling
water to the cylinder & the coolant return to cool the exhaust tract in
the leg, only to discover that the Seagull tiller arm fouled the adapter
plate, so provision for the Yamaha tiller arm/throttle was made in the
adapter plate.
To permit the Kingfisher cylinder fit, without it being too high, it was
found necessary to remove the exhaust stub from the base of the cylinder.
Up to this point Kingfisher crankshafts had always run in phosphor bronze
bearings reamed to 0.625” ID but the crankshaft was ground to 0.6235” to
give sufficient oil clearance.
Ball races with this ID, were & are not available & would have had to be
custom made, a very expensive answer to this problem, so the crankshaft
was redesigned with 17mm main bearing journals to suit a standard 6003
deep groove ball race, it was then found that while the lower crankcase
half, had sufficient meat to permit the boring of a 35mm hole for the
bearings, the top half would not, so a new meatier casting was designed to
cover this.
This all fitted together real nice but there was no provision for fitting
a fuel pump & the Yamaha tiller arm fouled the Seagull tiller arm stub,
this was just cut off, & the fuel problem answered by fitting a plastic
tank.
At this time the largest prop available from Yamaha for this lower unit
was a 7 ½” by 8” pitch which on a small hull allowed the power head to rev
at over 6000 revs, a bit too much for a motor that was designed to run
5000, so to prevent this Seagull had the props pitched up locally, to
circa 10”.
At some point a vacuum operated fuel pump was cobbled onto the crankcase
to permit the use of an external fuel tank, creating the 5R, a Seagull 5
with a remote fuel tank. This also needed a carb with a slightly smaller
fuel gallery to prevent flooding, as fitted to the pumped version of the
Kingfisher.
Now the problems with 15 year old Seagulls 5 & 5Rs.
First the crankshaft, to utilise a steel conrod with needle roller big end
bearings it was necessary to use a 3 piece crankshaft with a removable big
end pin made from a better grade of steel than the rest of the crank to
cope with the loads from the needle rollers, these bearing wear & as any
scooter owner knows it a simple job for your local scooter shop, they just
separate the crank halves & replace the conrod bearings & big end pin.
Not so with the Seagull 5, due to the design of the crankshaft with very
little support around the pin the hole tends to get slightly larger each
time a pin is pressed in place, & as con rods & pins have not been
available for about 10 years, when your big end gets tired all you can
change is the caged needle rollers, which means your using a worn pin &
conrod, so this set of needles won’t last too long. The next problem is
that the interference fit of the pin in the crank web holes is not as
tight as it should be often permitting movement during use, causing tight
spots & very rapid main bearing failure, hence the spots of weld often
found on these pins,& the next time the pin has to come out, the weld
usually damages the hole even more.
A proper repair on these crankshafts requires a new custom made pin made
slightly larger where it goes into the crank webs to give the correct
interference fit, a new steel conrod & new needle rollers to suit.
The only way I found to get con rods was to order 25 to be made for me &
Ross Leger in New Zealand, an expensive serious undertaking.
The next problem with these cranks is it’s location, it’s in close
proximity to the returning, leg cooling water. Where the lower half of the
crankshaft connects to the Yamaha drive shaft there is an oil seal to
prevent crankcase compression loss, below this the end of the lower main
bearing journal runs dry, that is until it come in contact with water,
often salty, causing surprise, surprise, rust adjacent to the oil seal,
which tends to start to fail soon after, a which point when you’ve used
your motor & it’s cooling down, water tends to be sucked onto the lower
main bearing causing corrosion on the balls, now as it has some corrosion
on it, it will start to run much rougher & hotter , on these crankshafts
they seem to run hot enough that the portion next to the crankshaft
expands to permit the crank to spin in the now tight main bearing,
wrecking the crank journal. Most Seagull 5’s died down this route.
When the bearings got this hot the outer diameter often stretched the
crankcase enough that the next set of bearings would rotate in the
crankcase necessitating a new crankcase.
If you leave a 5 standing for more than 6 months without a full bearing
change before use or at least a full strip down inspection, your going to
have a very expensive problem.
Seagull themselves drilled & tapped 3 holes in the steel centre of the
flywheel on the later 5,s so that the flywheel could be removed with a
special puller tool to prevent the hammer removal method stressing the big
end pin retaining holes & causing the early demise of your engine.
The next problem that seems to plague the 5 series outboards is corrosion.
The Yamaha leg that seem to last very well when used by them, but did not
seem to like, the very mixed metal environment of the Seagull & suffers
very badly so much so that the three 5’s I’m restoring. have all needed
new legs, perhaps Seagull should have used sacrificial anodes.
The adapter plate seems to love dissolving in water, I think it must be
made of a very cheap casting alloy, so much so that often the water feed
to the cylinder runs into the exhaust & seems to be almost impossible to
weld up, even when the white powder has been sand blasted away. So new
adapter plates & all the machining that needs.
The water cooled Kingfisher head that was used on this series seems to
have a life expectancy of 5 to 8 years before needing renewal, while the
cylinders last much better, expect to have to have the top face where the
head sits, resurfaced, when your cleaning out the water jacket & renewing
the head.
So if your bidding on this motor with a view to using it,
DO NOT START IT UNTIL IT’S HAD A COMPLETE STRIP DOWN,
you can total the crank in 10 seconds!
Nothing else will fit.
And if your adapter plate is in a useable condition be prepared to buy
yourself a good phosphor bronze Kingfisher for £350 to £450, spend £50 on
the machining & build yourself a Seagull 5 that you can use year in year
out.
Don’t worry I won’t be bidding, I can only see £50 to £75 worth of bits.
Good luck
Charles UK