merc running probs

[adamb]

I have a similar problem and have checked all of the above as well, how do you test crank seals top and bottom?

[Burty]

you would defo be down on power dude, you can see if a top crank seal is leaking quite easily but bottom ones are more difficult, check for signs of oil residue in the cowl base pan. if in doubt pull the powerhead and replace the seal as they are quite straight forward

[Jay Smith]

I have seen engine with the same problems lately ,it was the fuel lines seperating . Some of theses fuels are causing the inner hose to come loose from the outer jacket and shut off fuel and causing fuel starvation..

All good suggestions...
Jay

[143]

have seen this or something very simular before on a merc i had, the fuel line from the tank becomes week due to wether. ie heat and cold conditions through the winter months, when your demanding loads of fuel to get up and going the pipe callapses and restricks the fuel getting through... i know you may think that this sounds wrong as you seem to be going ok once at full throttle. but i would give this a go if you already havent as it worked for me. another thing that hampered the peformance was the bloke i bought it off had done the impeller himself and when replacing the gear box the tuner pipe was not seated correctly and after doing the pipe from fuel tank and this had the best out of it for about an hour.... dont think it was ever ment to go that well though as it then decided to stick a rod out the side....... if my memory serves me correct i think it also fell off the boat somewhere off lyme bay on the way back in.... ooops..

[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,

Did you ever get this sorted in the end? What was it?

Jim

[sean1982]

nope still playing up, its bogging down and popping all the way up through the rev range, number 1 plug is bone dry and the rest are black and oily. changed the stator, trigger, coils, leads, plugs, switch boxes, checked carbs, new base gaskets and crank seals.
gonna change the bleed check valves and check the reeds next.

[Superjetjim]

Originally Posted by sean1982

nope still playing up, its bogging down and popping all the way up through the rev range, number 1 plug is bone dry and the rest are black and oily. changed the stator, trigger, coils, leads, plugs, switch boxes, checked carbs, new base gaskets and crank seals.
gonna change the bleed check valves and check the reeds next.

Geez that sucks.. So poppings lean, which ties in with the No.1 being dry, once you've checked the valves/reeds might be worth swapping the carbs around to see if the fault moves to another cylinder - your in there doing reeds anyway (not sure if the jets are the same size in all carbs mind, figure they might get larger as you go down the bank due to lower pressure at end carb) easy to swap round though. Anyone got a spare set of carbs you could chuck on?

Not much else it could be.. Perhaps a loose or split fuel line going into top cars?

Jim

[Jay Smith]

Leak down test the engine you may have a tired motor with a bad ring ,bore health... They all need to leak down 10% or LESS... Any more than 10% on any hole tear down,hone and ring..

You WILL need to use a regulator with a red Holley as they are set up at 6.5 lbs I find the OEM Merc needle and seats will not seal off at a pressure any higher than 5 PSI and in rough water not even that much. Your regulated 4.5 PSI at the carb is dead nuts on ( If your gauge is accurate ) ..

Also see if your WOT top timing is advancing to full 25*. Sometimes the trigger wires become ridge and will not advance fully going to WOT and need attention and rerouting to free them...

Jay @ JSRE

[Nicolasticity]

Originally Posted by 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.

Have you ever had a back-fire during? seems a bit of a wild idea to me! I usually check carb main jets with a timing light to look at density

[The Docta]

Originally Posted by Jay Smith

Leak down test the engine you may have a tired motor with a bad ring ,bore health... They all need to leak down 10% or LESS... Any more than 10% on any hole tear down,hone and ring..

You WILL need to use a regulator with a red Holley as they are set up at 6.5 lbs I find the OEM Merc needle and seats will not seal off at a pressure any higher than 5 PSI and in rough water not even that much. Your regulated 4.5 PSI at the carb is dead nuts on ( If your gauge is accurate ) ..

Also see if your WOT top timing is advancing to full 25*. Sometimes the trigger wires become ridge and will not advance fully going to WOT and need attention and rerouting to free them...

Jay @ JSRE

Jay, XR2 (Race 200 model) was supplied new with a holley red and no regulator. Why would they do this is the pressure was too great for the carbs. I bow down to your far superior knowledge than mine, but this does seem a little strange.

[The Docta]

XR2 came with this one from what I gather:

http://www.summitracing.com/parts/HLY-712-801-1/

Marine version running at 5psi

[Jay Smith]

If I'm not mistaken the Holley Red when I've tested them will produce around 6 0 6.5 psi dead headed. ( needle and seats sealed/closed )

The stock coned type OEM needle and seats just have a hard time sealing espcially when a boat is bouncing and hitting waves. I've had better luck at 4 lbs tested at the carb...Anything higher seem to loose seal and flood ...

Jay