3.0 GS sometimes slowly looses power at WOT

[aerobat]

i happened to me one or two times last year and never again so i forgot it but today it happened again :

went out boating and the engine as usual started and ran fine without any issues. after the engine was warmed up fully i "gunned" my volvo out of trolling speed. the engine responded powerful and pushed the boat quickly on glide but after some seconds it slowly started to drop in rpm- very slowly and without any roughness, as you would slowly back off the throttle.

i retarded the throttle and the engine responded normal without any roughness, all was nice back at trolling speed , no signs of engine stall.

after few minutes i gunned it again and it this time kept the max rpm , all looked nice. after this i made a third attempt and again slammed the lever on table. the engine responded fine but after few seconds , just as i was about to rise the trim, started to loose slowly on rpm ( and the boat became slightly slower ) . i backed off again and aborted the ride , went back to our marina.

on idle when entering the marina it has some roughness and seemed to fire on only 3 cylinders for a moment , after a minute or two it returned to normal idle - it never stalled.

i pulled the plugs and all 4 look fine, maybe a bit on the lean side, surely not sooted. plugs are also brand new.

no water in oil, no water in the cylinders, no overheating ( it keeps stable at 160-165 even at WOT ) , no obvious signs of problems.

i have to say that it happened last year and also this year only when its really hot outside ( +30 deg celsius or +86 fahrenheit ) . a slow closing of the carb can be excluded- i hold the lever by hand on sure WOT .

does anybody have an idea ?

the engine is a 3.0 GS PNCA with a SX drive.

thanks much gents !

 

[skydiveD30571]

Re: 3.0 GS sometimes slowly looses power at WOT

It really sounds like a fuel delivery problem to me. When's the last time you checked the fuel filter? Have you installed a water separating fuel filter?

 

[aerobat]

Re: 3.0 GS sometimes slowly looses power at WOT

thanks skydive ! i,m also leaning towards its not getting enough fuel at WOT .

i have installed a water separating fuel filter last year brand new , the fuel filter on the pump was never touched by me and i do not know how old it is so i will change this filter also.

and now the confusion begins : i today bought a new filter but it looks different than my filter on the pump. i told this the volvo dealer in the shop but he swears its the correct filter !!! the new filter looks like a small oil filter , the filter i currently have on the pump looks more like "shot glass" .

can somebody bring light into this ? will it nevertheless fit an the design of the filter was changed or do i have the wrong fuel pump filter ???

 

[Don S]

Re: 3.0 GS sometimes slowly looses power at WOT

Part number of the filter you got would be handy, or pictures.
Here is what it should be.

View attachment Fuel Pump.pdf

 

[aerobat]

Re: 3.0 GS sometimes slowly looses power at WOT

thanks don, the filter on my boat is exactly the one in your pdf, i now have a sierra marine filter , unfortunetly i left it in the boat so cannot say the part number now.

but it definitly looks different ( bigger )

i found the correct filter at marineparts europe ( pn 3855104) and ordered it.

but i,m sceptic if it will solve my problem, especially when it only happens at really hot days. i would believe i deal with some kind of vapor lock .

have you ever heared or dealt with my problem on the 3.0 GS ?

 

[Don S]

Re: 3.0 GS sometimes slowly looses power at WOT

HOW TO: Testing your boats fuel system.*/ 283269

On the 3.0L engines, I would strongly suggest installing a water separating fuel filter between the tank and the fuel pump. That filter in the fuel pump is not a water separator.

 

[aerobat]

Re: 3.0 GS sometimes slowly looses power at WOT

ok, today my hopefully correct fuel filter arrived , the other was wrong for sure.



thats my fuel pump, i guess the 3.0 GS PNCA has a mechanical pump , correct ?



can somebody who has done it provide some hints how to best change the filter ? lifting the v clamp with a screwdriver or loosening the nut on the lower side of the filter housing ?

thanks !

 

[Don S]

Re: 3.0 GS sometimes slowly looses power at WOT

Here are the procedures.

 

[aerobat]

Re: 3.0 GS sometimes slowly looses power at WOT

thanks much for the very helpful procedure picture. amazing- the previous owner must have installed the old filter in the wrong way !!!

i installed the new one like described and also readjusted the idle mixture . had not the time to test the boat on full power but it idles and starts very fine.

don, when you would be a girl i would kiss you since without your prodecure posting i would install the new filter like the old one and that would be inverted .

.