AQ211 lacks power - mystery

[agskidmo]

Hi,

Im now 3 months into getting my boat back up to scratch after 15 long months out the water! 4 new exhaust risers and rubber hoses, 4 new outdrive hydraulic rams and piping, 2 fully serviced stripped and serviced DP outdrives, 1 cleaned up Rochester 2brl carb, new oil and filters, impellers, fuel filters, gear shift/throttle cables replaced, 2 new batteries, (2 re manufactured AQ211's fitted 3 1/2 years ago with about 15-20 hours on clock, scarcely run in (good compression!), B5 props that are as new due to low usage, all new anodes, new oil in serviced outdrives.. you get the picture?

Result

Engines sound amazingly sweet, revs up to 4k-5k in idle, slides into and outta gear easily, idles up n down river nicely, what about under power? Noooooo!!

One carb has been stripped and checked, new intake manifold gasket, washer replaced under power jet valve from fuel bowl, fuel was running down thru a break in original fabric washer, plugs are black!

Could my lack of power to BOTH engines be a coincidence? or rich running as a result of a bad setup?

They both rev up to only 2.2K under load at sea and sound as they should, but that's it, she wont plane. Compression ok, engine condition near perfect, hatch marks inside cylinders still there from the factory manufacturer. All was perfect 15 months or so ago.

Fuel tank had about 2 inches of old fuel, filters were changed, around 50-60 gallons added, so it should have mixed well with the old residual fuel. Colour of fuel drained from filters is more orange tinge that it should be, could this be it? common poor fuel quality to both engines? in idle and idle load shes fine, mechanical fuel pumps have been checked for pressure, anyone know if there is a fuel filter inside the fuel pump housing itself, perhaps this is the restriction? (2 external filters fitted before the pump, one after fuel tank, one just before mech fuel pump, both recently replaced)

Im now ordering new distributor caps (not been replaced for at least 5 yrs), new rotor arms, new plugs all round (15 hours on last ones 15 months ago), a new coil just in case this is the prob and maybe new HT leads (but these seem like new)..

Anyone got any ideas on why both my engines run perfectly in marina, but wont go beyond 2.2k revs when out at sea under load.. one engine misses now n then, pops and cuts out when back to idle up river, she restarts straight away tho, will blackenned plugs cause this?

The timing has all been checked by the mechanic and all work done professionally.

3 months later all I can get is 10 knots max (boat has been cleaned and anti fouled in last 2 month with hard racing a/f). Engine sounds sweet and grunts under load as she should, but sounds like some kind of restriction, air, or fuel when under load leading up to planning state.

Checked air intakes.. clear, fuel could be the only thing, its colour isnt perfectly clear with yellow tinge, more orangey but surely 50-60 gallons added to 2 inches of old fuel wouldnt cause an issue would it? the plugs being black may indicate a weak spark or over rich carb? its very odd both engines behaving the same (full power restriction) under load....
do electrical ignition systems (dist caps, etc) all deteriorate at same rate at the same time?

All ideas, however stupid, welcome, two V8's should be racing her through the water like she did before she came out of the water! (well maintained Princess Riviera 286 now about 250Kgs lighter since removing unwanted stuff!)

Complete mystery.

Thanks!
Adrian

 

[moonraker 36]

why not couple the engines up to a fresh container of fuel..so you no if its the old fuel or tank thats at fault.?i'm guessing they run of the one tank.
got to be somthing both engines are running off.

 

[exfinnsailor]

Think I would stop before you throw any more money into the hole in the water. Changing plugs and distributor caps could be a waste of time. If you get a crack in one you get a miss fire and not much else. Black plugs would suggest the mixture is to rich. What happens with the air filters removed.

1 cleaned up Rochester 2 barrel carb
fuel filters
B5 props that are as new due to low usage
New air filters
2 fully serviced stripped and serviced DP outdrives

Were the props on the boat to start with or are they new to you. Are they the right pitch.

Has everything been rebuilt / replaced bearing in mind it's a high revving petrol engine and not a slow revving diesel.

 

[pappaecho]

For an engine there are two main ingredients - air and fuel. If the fuel is not the culprit, check the air cleaners, or better remove completely and re test. It could be something silly like both airfilters inserted wrongly, resulting ina lack of air under load

 

[markcw]

I had old fuel in my boat when i brought it, looked the same colour as you have mentioned. i suspected it was 2 years old, as the boat had been for sale in the boat yard for nearly 1-5 years.

best way to tell good fuel is removed half a cup from the tank and light it in a dish in the garden, if the fuel woooosshes up you have good fuel, if the fuel smolders and burns slowly you have bad fuel,

Then go to halford and buy a petrol additive that boost petrol back up to 95-95 octane, empty into tank and try to bounce and mix the additive in, then light up another sample and review.

By the way my boat ran lovely on old fuel just lean it off, black plugs is to rich, also remember my V6 had hot plugs in so i changed them for standard plugs and what a difference it made.

The other to check is the air gap in the electronic spark module inside the distributor if this is wrong it will give you a weak spark, that was one of my mistakes when i upgraded to a 12v ignition system rather than the standard 8v

mark
V/P v6 4,3gl 430b

 

[essexboy]

Power loss

Not an expert on Rochester carbs, are the secondary barrels vacuum operated? could be running on primarys only.