merc running probs

[sean1982]

still having problems if anyone has any ideas? bogs and struggles untill it gets wound up an gets going. changed all the electrics, i have 4.5psi fuel pressure. its revving to 6500 but it takes ages to get there and i have to trim alot more than i usually do.
last year it would wind up real fast and just out of corners.
could it be a fuel pick up? or carbs need cleaning?
cheers

[sean1982]

link to video
http://www.boatmad.com/forum/showthr...351#post202351

[Superjetjim]

Originally Posted by sean1982

still having problems if anyone has any ideas? bogs and struggles untill it gets wound up an gets going. changed all the electrics, i have 4.5psi fuel pressure. its revving to 6500 but it takes ages to get there and i have to trim alot more than i usually do.
last year it would wind up real fast and just out of corners.
could it be a fuel pick up? or carbs need cleaning?
cheers

Sean, most likely carbs are partially blocked pull them and strip/clean with a tooth brush and carb cleaner. Whilst your at it replace the fuel pump diaphragm in the fuel pump (rebuild kits on eBay for little money) - it'll be one of those two items I would imagine. You could try pumping your fuel bulb when your at the hole shot to test before you strip it - if it picks up as it should its most likely the above. Should be able to do the above in an evening easily - Clymer manual is really useful, or clicky here:

http://1manual.com/Mercury%20manuals...ual_Index.html

Jim

[Superjetjim]

http://1manual.com/Mercury%20manuals.../878079/3a.pdf

Section 3A has what you need for the fuel pump..

Jim

[sean1982]

im using an electric holley red top pump with a reg set at 4.5psi, 3/8 lines and a fuel water seperator all new this year, changed from a facet red top with reg

[Superjetjim]

Originally Posted by sean1982

im using an electric holley red top pump with a reg set at 4.5psi, 3/8 lines and a fuel water seperator all new this year, changed from a facet red top with reg

Strip/clean your carbs then.

[The Docta]

Didn't think you needed a regulator with a red top assuming it is the right model. Plus, isn't 4.5 at the very bottom end of the range?

[Hydrostream]

Originally Posted by The Docta

Didn't think you needed a regulator with a red top assuming it is the right model. Plus, isn't 4.5 at the very bottom end of the range?

Yep, I've never used a reg with a red. But as long as theres volume he shouldnt have an issue. Its about volume more than pressure with carbs.

Pluss, if it ran before in its current setup, no reason it shouldnt now.
Unless the reg has changed and its over fueling at holeshot causing a bog.

Check all the bleed lines for splits or cracked ends.
Check the reed valves.

Try bumping the key in for choke when you take off, see if it gets worse r better.

Has your idle changed at all since the problem started?

Is the motor still making the same RPM at full throttle?

[sean1982]

motor is struggling to full rpm, i have to trim it up more to try and keep the revs up, one of the bleed lines was cracked but changed it and no difference.
reg is new but tested it and its putting 4.5psi out, il try taking it off.
i have removed the spark advance box and set max advance to 23 degrees.
think we had to play with idle timing too? could it be that?

[Burty]

i thought max advance was 25 degrees??

[sean1982]

wanted to play it abit safe at 23.

[Hydrostream]

If you've ditched the spark module, set max to 25 deg.

If you have played with the pickup I'd start there, set the trigger arm at split case to start with. It will idle high but I presume youre starting in gear.
It will leave better here.

doesnt sound like your problem though, if your down on rpm too.
I'd look at a coil possibly or plug leads.

Have you changed the plugs? What plugs you got in it? If your using surface gap, I'd lose them and put gapped plugs in.
Are all the plugs colouring up?

Rule of thumb, lose 800rpm for each cyl down.

[sean1982]

It's not loosing rev at top end I don't think, we put a brand new stator new plugs new coils coil leads switch boxes wiring trigger, tested them all and there all firing. It just takes so long to wind up

[baj666]

compression test each hole

[sean1982]

115 on each cylinder

[larby]

As hydrostream mentioned earlier, have you checked for flow volume as well as pressure? It's possible for it to have great pressure but will still have issues if flow is down...

James

[Hydrostream]

Just a thought, but put a clear hose from the pump to the motor, see if there's air getting in anywhere.

Is the cam on the carbs set up correctly? Set it just off the roller.
Are they pumper carbs?

[Superjetjim]

Does sound like partial fuel starvation - is it hardening off under load?

I'd still suggest a strip clean of the carbs - the tiny low end holes could be varnished/gummed/part blocked causing the poor take off at max fuel demand with minimum air flow into cases.

It's a cheap easy one to do and tick off the list before chucking more cash at parts.

[Germansaleen]

hi
i test my fuel problems sometimes this way
do a run without the engine cover , put some fuel in a spray can/pump can and spray a little !! ammount of fuel at 6000 with full open butterflys in the velocitys of each carb,first top and later mid and lower, if you feel a difference and rpms come up it can be a fuel pressure/volume problem.
if power goes down , because of to rich.... normaly you have enough fuel in the bowls

best is a spray can that has a nozzle to atomisation the fuel in a light mist of air and fuel. windowcleaner bottles are fine.

i had the same problem on a modified rotax sea doo engine ,i changed all elektrics and ended with one bad crankshaft seal and it had very low cranshaft pressure to get the fuel into the cylinders.

[sean1982]

could a lower crank seal do this?