Mercury V6 Cutting out under load

I have a Mercury 175 V6 1981 - Blue Band.
Was running fine last year. Serviced etc. Although I did notice some deterioration, didnt seem to sound as smooth.
Winterized it.
Then this year, changed the plugs, impeller, and ran Quicksilver Powertune throught the Carbs which seem to clear a fair bit of crap out. Seems cooling maybe working better too after impeller.
Ran it in a tank and it seemed to run very smooth, no problems, then i can travel about 200metres in gear at 2-3000rpm and it loses power and then cuts out.
Again ran it in tank and seemed smooth. Then took it out and it cut out again under load. it only seems to do this under load.
I cant see any obvious fuel line problems and have used brand new fuel and new quicksilver oil at 50:1.
i have run it in a tank again it seems to be missing now???

Please help....its killing me and i know the engine has been well looked after and mainly run in fresh water.

Please help. Thanks. Joe

Re: Mercury V6 Cutting out under load

Welcome to iboats Joe!

Check compression, should be over 100 on all cylinders and within 10% of each other. Check spark and make sure you have a hot blue one. Check all fuel lines for cracks and loose connections. Does priming the bulb before it dies help?

Re: Mercury V6 Cutting out under load

Hey Plainsman.

Thanks for the reply. I had the compression checked at the end of last year and was fine apparently. Not sure how to check sparks apart from at night. Fuel lins seem ok but i am going through them, probably replacing each bit. Havent tried priming the bulb before it dies but will as it is a good suggestion. I think it leads to a fuel starvation problem so am checking the fuel pump and the filter etc .....but who am i to say?!!?

I would appreciate any other tips or ideas

Thanks

Joe

Re: Mercury V6 Cutting out under load

You can get a spark tester at any auto parts store. I asked about priming the bulb because if it helps, then the fuel pump needs a rebuild. The carbs may need a rebuild and good cleaning as well.

Re: Mercury V6 Cutting out under load

thanks again
certainly makes sense. The more i have read the manual the more i was getting suspicious of the fuel pump. Took the cowl off and pumped the primer bulb without the engine running and it might have been my imagination but thought it sound as thought the fule pump was sticking. Fuel didnt get through and then with a slight click it did.
I have an expert having a look on thursday. I just havent got the time to waste. Thanks.

Re: Mercury V6 Cutting out under load

Joey,
I've got an '81 150 with similar problems. Very interested in knowing if you've made any progress.
Thanks