won't run under "load"

[elwopo]

Hello,<br />I have a 1996 Force 120 with 40 hours on it. Just had head gasket replaced and took it out to test. I ran it slow for about 3 minutes, then opened the throttle. Ran great for about 1 minute then rpm dropped. Runs normal at 2000 rpm. If I try to go over that, it "bogs down" and won't run well. It idles perfectly and will run normal at all rpm if prop not engaged.<br />Any ideas would be greatly appreciated.<br />Thanks,<br /><br />Tony

 

[roscoe]

Re: won't run under "load"

Welcome to iboats.<br /><br />Have to ask, why did you replace the head gasket?<br />What caused its failure?<br />Was there any other damage found when the head was off?<br />Was the head torqued properly, in sequence, to the correct specs?<br /><br />Next step, check the compression again.<br />Then check for a strong spark.

 

[elwopo]

Re: won't run under "load"

Hi, and thanks for the welcome.<br />Head gasket was replaced by mechanic. I took it in after being stranded twice. When running at slow speed for 30+ minutes (long no wake zones), the engine would suddenly shut off. Trying to start again, it would act as if battery very low. Starter would be extremely hot to the touch. If allowed to sit, engine would start and run fine. Mechanic told me 1 cylinder compression was low due to blown head gasket. He said this allowed heat to escape so the engine would sieze up and starter couldn't turn it. I got boat home and tried to start it. It acted if battery extremely low. Starter would (sometimes) make contact and only crank 1/4 turn. Guy at the parts place told me starters can burn up if allowed to get too hot. I replaced starter myself and started great. Tried to take it out last night....and now....new problem!<br /><br />I suppose I can buy a compression tester...but how do I check for strong spark?

 

[roscoe]

Re: won't run under "load"

Hmmm, this could be a number of things, but so as not to send you off in 5 different direction, lets start with a compression check.<br /><br />You can buy a little spark checker, plugs into plug wire. Or you can hold the plug with an insulated pliers, and check that you have a strong blue spark on all cylinders. Spark should jump from the plug to the block when you hold it 3/8 inch away.<br /><br /><br />Seems strange to me, that a blown head gasket would allow the engine to get hot enough to seize it up. Seen plenty of engines run on 3 cylinders due to a bad gasket. They didn't run well, but they didn't seize up.<br /><br />Maybe someone else has an opinion to add here.

 

[imported_bjs]

Re: won't run under "load"

can you touch the engine block after you run for a while?for being hard to start might loaded up with fuel.or the starter could be bad!carb problem maybe you need to check if both carbs are opening take back to mech.cause he didnt fix the boat.something caused the head gasket to blow or was gasket blown.ask if you can see old head gasket you can tell if gasket is blown.<br /> good luck!!!!!!

 

[peacekeeper6]

Re: won't run under "load"

i had this problem on the water yesterday. turns out i had something clogging one of my carb intakes in the bowls. hope that helps.

 

[elwopo]

Re: won't run under "load"

Hi Everyone,<br />Thanks for all the helpful suggestions. It does seem as though it was a fuel issue.<br />Compression seems fine. I've got 130 in two cylinders and 140 in two. I used a can of decarb, changed the fuel filters, and the plugs.<br />Now there is a slight new wrinkle.<br />Took it out yesterday to test. Ran great WOT for 10 minutes this time...then died. I took the cover off to see if anything was overly hot, everything was fine. What I noticed was the new inline fuel filter (clear this time...not like factory one) was empty. I checked the primer bulb and it was soft. I pumped it until the fuel filter filled and was able to start the engine again.<br />Anyone know what causes this? I can't understand why it would be fine for 10 minutes then lose fuel. Could there be an air leak of some kind?<br />Thanks again....I think I'm getting closer to having this thing actually running right.<br />Tony

 

[roscoe]

Re: won't run under "load"

Ok, you have spark amd compression.<br />That leaves fuel system.<br />Line could be sucking air, or pickup in fuel tank could be obstructed by junk.<br /><br />Inspect tank, remove pickup if need be.<br />Replace the entire fuel line and bulb with a new quality one.

 

[eurolarva]

Re: won't run under "load"

Might want to rebuild the fuel pump as well. Pretty cheap and easy to do. Did motor race when it died. Usually with an air leak it creates a lean condition causing the motor to race. Also check the o ring at the fuel quick disconnet.

 

[elwopo]

Re: won't run under "load"

I'll replace lines and bulb to be safe...they are pretty old.<br />There was no racing of the engine. The rpm just dropped quickly then it idled rough for about 15 seconds before it shut off.<br />Where can I find instruction on how to rebuild the fuel pump? Is it available online?<br />Thanks again for all the help!!

 

[rbruce63]

Re: won't run under "load"

Have you guys checked the water pump's impeller? it seems to me that if the motor overheated it seized, then, blew the head gasket. I would overhaul the waterpump and check if there are obstructions in the water tube then I would address the other things!

 

[roscoe]

Re: won't run under "load"

Fuel pump rebuild is easy.<br />Buy the kit from any Merc dealer, mine came with instructions. <br />About a 25 minute job.

 

[byacey]

Re: won't run under "load"

Did you check the head for flatness when you replaced the gasket?