Power loss over entire Range?

[DistantGunfire]

Hi,
The last few trips out with my 70's model 105hp chrysler have felt to be lacking in power.

My boat is a 15 foot Volero Arrow and my top speed is about 35mph on a 19 pitch prop.

Now the problem I have is the engine seems to be down on power. I often tow 2 tubes behind the boat and taking off and getting to plain isn't usually an issue. Now it is somewhat. The engine struggles to get up and going. Once on plain the power seems ok but not what it was.

The idle is quite rough now also. The engine starts no worries cold. Hot starts can be hit and miss with it sometimes dying from too low rpm but on the second crank they slowly come back up. Neutral idle is around 1500rpm. 7-800rpm in gear. But rough.

I have noticed the engine is smelling of fuel when running. Like its running rich. The idle screws are both aprox 1-1/4 out from seated.

When I first got the engine a year ago I replaced the fuel pump, water pump and housing, all fuel lines, fuel filter between fuel pump and carb, new primer bulb, new tank. I also cleaned and sync'd both carbs. It has been out many times but only now am I seeing a decrease in performance. It just doesn't pull like it did or idle for that matter.

Could this be an ignition/spark related problem or something more sinister?

It definitely smells as though it is running too rich or is not firing properly. Plugs are gapless new NGK showing a blackened centre electrode and oil on threads when removing from head.

Oh and compression on all 4 is between 145 and 140 psi.

Any help appreciated!

 

[DistantGunfire]

Re: Power loss over entire Range?

Is it possible I simply have the idle screws set too rich? Can this cause a rough idle jumping a hundred or so rpm and power loss?

As a side note that is worth noting. When I touch the head with the engine running to check temp I get a MONSTER zap!!! Could this be the issue?!

 

[pnwboat]

Re: Power loss over entire Range?

You should not be getting zapped. Sounds like insulation on the plug wire(s) or the spark plug boot is not doing it's job. It may or may not have anything to do with you problem. Usually bad plug wires causes the engine to mis-fire. Regardless, it should be corrected.

Squeeze the primer bulb 4 or 5 times (I'm assuming you have a primer bulb). It should get good and firm. If not, then a needle valve in the carb may be sticking open. Only takes a small piece of gunk to keep the needle valve from closing all the way. Could also be a bad needle valve. Depending on the design, the needle valve may have a small rubber tip in the end of it. If it does, it's not uncommon for them to wear out and stop sealing when closed. If it doesn't have the rubber tip, make sure the float level is set correctly. If the float level is set too high, then motor will run rich.

 

[DistantGunfire]

Re: Power loss over entire Range?

Thanks for the reply pwnboat.

The carbs needle and seat are clear. Carb float adjusted spot on. The primer bulb is hard after priming.

I am going to purchase some new leads and fit them up. Hopefully this is the cause of the erratic running and loss of performance. It is arcing that bad that last time we were out I remember touching the hydraulic motor and that zaped me too! I would say the leads are fried!

Any other ideas or input welcomed

 

[pnwboat]

Re: Power loss over entire Range?

Looks like you've covered all bases with the carbs. Change the wires and hopefully that "cures" the problem.