HPBCANADA.COM

Ok folks
I have now got my larger bore 70hp carbs on my motor (got a set from a member on here sent to me in the uk).
I have started the engine up and its rough on tick over but perfect once its over about 1500 rpms.
Now from what I know the 60hop and 70hp is the same timing settings !!!
the only thing different between a 1995 60 and 70hp was the size of the carbs, so now ive got these on its a 70hp.
Now what would be causing a rough idle ? or do I have to do a complete re-sync with the timing
and carbs ?
I am 99.9% sure the max advance on both 60hp and 70hp is 17 deg btdc.
But I also heard that 19 was best and in a bulletin a while (not 100% sure on that )

with the slow running screws would around 1.5 turns from fully seated be a good place to start with ?
then around 1/4 plus or minus each way ?

Unless these were brand new I would tear them a part and clean these new carbs as it sounds like your low end might be clogged and dirty.

cheers Dubber
that is a possibility.
good thinking that man.
also a big difference in Canadian petrol and the stuff we get here I suppose.

I will give them the once over though, not a hard job once they are off.

thanks

So......did it work?

Hi Dubber
not sure yet only just cleaned the carbs tonight.
they did not look too bad to be honest, but floats were all over the place.
I did find the tiny holes up in the top of the venturi all had a tiny bit in them, but not as much as I would of expected to be honest.
I am now thinking I had the idle screw way wrong.
from what I have gather they should be about 2 1/2 turns out then 1/4 turn either way.

you know when you get something in your head telling you different ???
well I was putting them at 1 1/2 turns then trying !!!!!! doh

that is the setting for my little Suzuki 30 and a couple of other little industrial engines I have.
I have also gone through all my notes on these engines to make sure I am not cocking
up anything else .

hope to test the boat one day this week coming.
first i will set it up in a water butt for half an hour or so, then go to river for a blast.
its been so miserable the weather here the last week.

i will post results as soon as i get it down the river, i am hoping to see another 4mph f
by putting on the carbs taking it up another 10hp.
That might not sound much with the big engines, but from 60 to 70hp is a big increase.
But jut have to wait and see what happens.
.

So did you get a chance to get out and blow this powerhead up yet under London bridge in front of the Duchess of Cambridge with all the extra gas you are pouring down it with these new carbs?

No not been out just yet
been a little bit busy on a couple of dry days and the rest have been very horrible wet n windy days.

I probably wont get down to London bridge until the spring, I do all my testing on the upper thames where there is a 8mph speed limit ha ha

I am now waiting for next dry day to go seeing what it can do, ive had it running in water butt and its running very nice.
will give it a fine tune once idling down the river to make sure its not lean on any carbs etc.
then I am going to see what it will do.
My target at the moment it to get over the 45mph barrier, this I know is not FAST by race boat standards, but its
fast for a Orkney dory.

while I am waiting for a break in the weather I am still looking for a bow lifting prop that's cheap enough.
its like looking for rocking horse s**t, nothing seems to be coming up on the for sale sites at the moment.

do you know what makes of props are good bow lifters that fit omc 13 splines ?

The extent of my OMC prop knowledge would be that you would need some sort of a raker. You may have to wait until the January transfer window during the EPL season for a dry day...

yeah I can only think of a raker to give the most bow lift that will fit my engine.

idealy a 13.5 x 22 pitch.

I don't think my engine would swing the 24 pitch much good on the holeshot, but would give it a try.

.