Engine problem Volvo Penta 145AQ

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ontheplane

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Hi all,

I've spent nearly £2000 to get a local "engineer" to try and fix a running problem on the boat, but to no avail, so I've decided to have a go myself....

Problem is as follows...

Engine revs gradually increase ok up to a maximum of 3200 rpm then engine bogs down and dies back to about 1000rpm.
If you open the throttle suddenly the whole thing just gets bogged down.

I removed the Flame arrestor and air filters over the twin solex carburettors - tried again. Engine now revved up to about 3600 rpm, and the boat was trying to climb on the plane but couldn't (suggests over-pitched prop) but at least the engine wasn't bogging down any more. Lots of petrol fumes/vapour coming out of the top of the carbs but it was at least running better.

Tried again but only replaced the air filters - bogged down.
Tried again but only replaced the flame arrestor - bogged down

The bogging down always happens at around the same rpm no matter what the loading in the boat.

My initial diagnosis is that the engine is being flooded but my problem is this...

Why is this happenning, and why are the Air filters and flame arrester clearly restricting air-flow so much?

More importantly, what can I do with it?

Thanks to all,

Grant
 
First thing I would do is try to get some money back from the engineer since he has clearly done [--word removed--] all.

Have you tried new airfilter? This is probably worth trying, though I don't know what can be done about the flame arrester. Assume this happens with no load on the engine i.e. out of gear also?
 
No, the problem ONLY happens when the boats in the water, in gear under load. Out of the water it will rev very happily as far as i am willing to take it!

The "change air filter" idea was one I had, but then the flame arrester will still cut airflow down - I think I need to increase airflow and reduce fuel slightly. The carbs are Solex - they appear to be single rather than twin choke.

My dad who's pretty good at these things thinks the jets are too 'big' and are putting too much petrol in which is causing it to be choked up.

I am also peeved that with a 15in pitch prop it STILL won't get over the hump - again if it's being choked off it may be down on power.

Can these carbs be adjusted across the rev band or is there only an idle mixture adjustment?? Can I get smaller jets?

Thanks

Grant
 
Hi i stand to be corrected on this ,,have you checked the diaphrams in the carbs,, im pretty sure these carbs have them,,it sounds to me like your not getting enough fuel,,have you checked the colour of the plugs once the engine has died,,if the engine is running lean you can snap the throttle open and it will rev,,under load you can bring the revs up slowly,,but the engine is not producing any real power to get you on to the plane,,spannerman will be along shortly to give you a proper answer,,good luck
just had athought ,, i think your only running on one carb thats why the engine revs drop back because its running out of fuel,, anyway as i said i stand to be corrected
 
Thank you.

Would this explain why it's working without either air filter or flame arrester but not with either??

If it is diaphrams I'd be chuffed as that should be a fairly easy fix.

When the engine is running without air filters or arrester, there is an awful lot of fuel coming back up out the top of the carb - would this also be down to damages diaphrams?

Thanks

Grant
 
is fuel comming out of one carb or both,,
in my thinking it would if only one carb is working ,,the fuel pump is trying to supply two carbs if one is not working then it will start to flood(old carbs etc),,as i said istbc
an engine will rev free and hard when running lean,,ie without an air cleanner or any obstuctions,, but not under load
 
i would still look at the plugs ,,,once the engine bogs down ,,turn it ioff and pull a plug , atleast you know which way your going
 
were they clean when they went in,, i still think you running lean,,white spots mean heat and lack of fuel,,i could be running you up the wrong path,,without seeing the engine its hard to determine a fault,,their are so many variables..the other thing is white spots indicate you might have water in the fuel,,,i hope not
 
Hmmm water in the fuel would be bad - although curable - although I left the tank full over winter to reduce condensation. The plugs were new after the last service, and I had the problem then...

I think you are on the right lines - it's either running rich or lean - but if lean, why does the air filters/flame arrester cause the problem and removing them cure it?

It's a puzzler...
 
does removing them cure it ,,out of gear,,and revving in neutral,,or in gear , when the motor is pulling hard
 
good question,,i have been looking at plugs for 25 years,,thats how you read an engine,,full power run ,and switch off,,unless its anything mechanical ,,its the only way to tell how the engine is running,,its the only way to get a base of where to start to look for a fault in the set up-still,,,istbc

looking at plugs for 25 years,,,i must be a boring old fart,,,still i like it
 
Although the problem does seem to be carburation have you checked all base settings eg ignition and cam timing,i may be wrong but i seem to remember that these engines have a lot of valve/piston clearance so they will run with the cam timing a tooth or two out without lunching themselves but obviously down on power,may explain fumes out of carb or then again i may be talking B******S
 
Before messing about with the fuel system, have you ensured the ignition basic settings are correct?
1. Have you checked the point gap/dwell angle?
2. Have you checked the ignition timing with a strobe?
3. Using the strobe ensure the mechanical advance is working.
My AQ110 is very suseptable to the slightest error in dwell angle and ignition timing.
 
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