Help with 115 hp inline 6 mariner WOT

[andersonspartsplus]

Hope someone out there can help me out.

This is a 198? 115hp Mariner with power trim 6 cyl inline, 3 carburetors and diaphram type fuel pump
New spark plugs installed
Prop redone
lower unit gear lube changed
new impeller

Put the boat in the lake and after it warmed up, went to WOT and it was great same as always. After docking it and heading back out it is surging at midrange and at WOT it is only moving about 15 mph. The engine sounds like it is bogging at WOT. Doesnt seem to misfire, just doesnt have any power.
Runs perfect on the muffs and in neutral. In neutral it will rev with no hesitation at all. I changed the fuel tank with a new tank. Also doesnt seem to help squeezing the primer ball.

The carbs are dripping with fuel and it seems to be using an excessive amount. I noticed bubbles in the inline fuel filter near the pump. Is this normal?
Should the primer ball soften up at WOT?

Starts and idles just fine. Runs on the muffs fine. Again in neutral it revs as normal but under a load the motor wont pick up rpms like it always has before.

I have experianced a bad prop before, Motor screams boat doesnt move....thats not whats happaning here. At WOT it acts as though its only running on 4 cyl.

I keep coming back to a fuel issue because of the excessive fuel dripping from the carbs.

I checked for spark when its cold and hot...has good spark both ways.

Any ideas would be greatly appreciated.

 

[CharlieB]

Re: Help with 115 hp inline 6 mariner WOT

First check for flooding carbs, with the trim level, squeeze the primer firm and hold it while watching all the carb throats for signs of fuel flooding. Any leakage, rebuild all carbs.

Just because you have spark at idle doesn't mean you have adequate spark at higher RPM. The stator/dual switchbox system has two sets of charge windings in the stator, cranking/low speed and high speed windings. A hot 7h spark cranking/idleing does not test the high speed windings.

Either DVA test the stator as spelled out in the CDIElectronics Ignition Troubleshooting Guide, (available for free0 at their web site), or use an inductive timing light and see if the light fails at the RPM you begin to have the problem.

PROVE the fault, a stator costs $$$$, you do NOT want to buy one if it is NOT the problem.

Testing on the hose is worthless unless you are DVA testing, as a simple spark test will still pass without the prop in the water and the motor in gear, placing FULL LOAD on the ignition system.

 

[andersonspartsplus]

Re: Help with 115 hp inline 6 mariner WOT

Thank you for your help...that makes sense.

Can the DVA test be preformed under no load circumstance?

If I squeeze the primer ball and fuel flows from or the throat of the carbs get excessively wet your saying to rebuild the 3 carbs?

Would the bad stator windings only take out 1 or 2 cylinders?

What brand fuel pump and carb rebuild kits would you recommend? OEM? If offered is aftermarket ok?

Thank you for your help

 

[79Merc80]

Re: Help with 115 hp inline 6 mariner WOT

I have an 84 Mariner 90hp inline 6. At idle and up to about 2000 RPM, it was running on all 6, above 2000 RPM, #1 shut off completely and #3 was intermitten, so yes, the stator can take out one or two cylinders.