suggestions for next steps? shot rings? time for rebuild?

Mercruiser 260 5.7 350 V8.. <br /><br />Okay here is my story in a quick review...<br /><br />Last summer had overheat situation.. didnt get excessively high but ran right under the red for a very prolonged period of time at very low speed.. (long story and yes it was stupid).. pulled plugs after run and were oil fouled<br /><br />boat got a full tuneup at shop when took it in for overheat.. they didnt fix the overheat by the way.. <br /><br />i later fixed overheat problem<br /><br />Fixed shift cable that went out<br /><br />Ran boat again. Didnt overheat was at good op temp but after going back to idle started running a bit rough and stalled when going into gear.. friend close choke down a bit when i shifted and it went into gear and ran.. thou again rough and idle never stalled at idle.. and again had ot have friend close choke down a bit.. to get back into gear.. pulled plugs again and again oil fouled<br /><br />figure bad fuel to air mix so checked fuel line.. found bad antisiphon valve.. fixed it.. fuel flow to carb fixed.. <br /><br />ran again..again ran a bit rough at idle.. and had hesitation when going into gear but not always stalled.. stalled once but mostly just hesistation then into gear.. <br /><br />got back.. pulled plugs.. fuel fouled..<br /><br />winterized the boat<br /><br />went to unwinterized and noticed fuel in the oil..<br /><br />changed the oil.. adjust carb needles to 1.5 turns out.. <br /><br />got boat started.. no leaks anywhere.. no water in oil.. but idled a bit rough at first but picked up.. <br /><br />had vacuum gauge on.. ran at 10-12 pretty steady no huge fluctuations at idle which is low.. <br /><br />throttle up and down quickly and gauge went from 0 to about 20.. and back fired<br /><br />any slow throttle up and it hesitated.. a bit<br /><br />I need to do a new comp test now that i have a new started battery.. didnt trust the old batt but when i did it with old it was 100 in 1 cyl and 125 in the others.. i guess even with low bad that 1 cyl stand out as a problem.. <br /><br />note that every time out on the boat after the overheat was short and just to test the result of the overheat fix.. shift cable fix.. and fuel flow fix.. <br /><br />i am fairly new to this boating thing but enjoying the hobby... just looking for some suggestions.. time for a leakdown test? Anything else? These results already clearly pointing to shot rings? <br /><br />I would like to avoid playing $1500 for a rebuild if possible but am not going to shy way from spending the money if thats the right thing to do...<br /><br />Thanks for the help/thoughts.. kind and unkind words..

Re: suggestions for next steps? shot rings? time for rebuild?

Do a compression test....<br />Is there any evidence of fuel in the clear tube that goes from the fuel pump to the carb?<br />If there is you need a new fuel pump....<br />Change the water separating fuel filter, too.....<br />It may be a carb problem as well....JK

Re: suggestions for next steps? shot rings? time for rebuild?

Do a compression test....<br />Is there any evidence of fuel in the clear tube that goes from the fuel pump to the carb?<br />If there is you need a new fuel pump....<br />Change the water separating fuel filter, too.....<br />It may be a carb problem as well....JK

Re: suggestions for next steps? shot rings? time for rebuild?

hey thanks for the thoughts.. no fuel in tube.. .. i got a a new fuel filter as well.. flow to the carb is good.. i actually have a reman carb that ill throw on there this weekend just to see if it makes a difference.. <br /><br />and ill redo the compression test.. thou I really expect similar results.. <br /><br />thanks.. ill follow-up this weekend..

Re: suggestions for next steps? shot rings? time for rebuild?

i actually have a reman carb that ill throw on there this weekend just to see if it makes a difference..

Click to expand...

If that's a Marine rated Carb.,.......<br />I Think you'll Cure the Fuel Delivery Problems Too......

Re: suggestions for next steps? shot rings? time for rebuild?

bondo.. yup it is a marine carb.. i hope thats the case.. will find out on sat...

Re: suggestions for next steps? shot rings? time for rebuild?

those plugs are probably not oil fouled, probably carbon fouled,,,,,from running rich. Idle mixture srews should be set while engine is idling to acheive highest possible rpm, then reset idle to specs

Re: suggestions for next steps? shot rings? time for rebuild?

also, your vacuum seems low at idle, check for intake leaks. After the overheat, you may have caused an intake leak, which would explain your poor idle.

Re: suggestions for next steps? shot rings? time for rebuild?

scott. thanks for the feedback..<br /><br />at the time i felt pretty sure the plugs were mostly oil fouled.. they were wet not so much powdered with carbon... <br /><br />the vacuum is definitely low at idle.. <br /><br />and the idle mix screws.. man how the heck do i get to those screws.. does anybody else out there have a merc 260? The damn therm housing makes it pretty much impossible to get to those screws while the engine is running.. <br /><br />i got the carb adjusting tool but the damn thing doesnt fit in there.. how the heck do you do it?? <br /><br />Thanks

Re: suggestions for next steps? shot rings? time for rebuild?

qote:<br />------------------------------------------------<br />Last summer had overheat situation.. didnt get excessively high but ran right under the red for a very prolonged period of time at very low speed.. (long story and yes it was stupid).. pulled plugs after run and were oil fouled<br />qote:--------------------------------------------<br />need to do a new comp test now that i have a new started battery.. didnt trust the old batt but when i did it with old it was 100 in 1 cyl and 125 in the others.. i guess even with low bad that 1 cyl stand out as a problem.. DID IT CHANGE WITH NEW BATT>if not-<br />----------------------------------------------<br />comp test show low in #1 cylinder by 25psi (probly from overheating) trust that result that you do have problem there,gasket,valve,head warp, you may need to go deeper into the engine for this fix.<br />I hope its not that deep but the #1 cylinder has the thinest wall so overheat will efect #1 first keep that in mind. 10lb fluxuation no problem 25lb ehh mabey a problem.<br /><br />to get to your idel mix screws try a cable (flex drive)screwdriver.You could make one of those.<br />good luck with your repairs.<br /><br />ScottF has a good point as well. as they all do!

Re: suggestions for next steps? shot rings? time for rebuild?

PS to better trouble shoot your compresion problem,add 1 taespoon of engine oil to the #1 cylinder, crank over engine a few turns and do another comp. test, if the pressure goes up you have ring damage if it stays the same you have valve damage.

Re: suggestions for next steps? shot rings? time for rebuild?

hammer/time,<br /><br />i did the oil in cyl 1 late last year and it did increase compression a good bit.. note that cyl 1 was the first cyl i test so had the benefit of the least amount of drain on the battery.. <br /><br />but assuming that oil seals the ring and oil is in the engine when its running.. does that imply that its okay to run this way? if the comp with oil brings it in line with the other cyls? That part isn't clear to me.. <br /><br />Thanks

Re: suggestions for next steps? shot rings? time for rebuild?

I am a bit more than a little confused.<br />I read and reread hoping to understand what<br />condition your motor shows that has you<br />doing compression and mechanical checks.<br /><br />If your motor is running rich then why check<br />fuel flow, ie filter, pump, fuel line?<br />I would think it is getting plenty of gas.<br />Stuck float, blown power valve, spark timing,<br />poor low stage spark. IE plugs breaking down<br />coil, ign wires, condensor, cap, rotor.<br />I know you had a tune up. If the repair shop<br />didn't fix the "over heat" then are you sure they<br />tuned up right?<br /><br />Hot oil will promote wear. Camshafts do/have<br />gone flat. This will change fuel air mixture<br />requirements.<br /><br />Low comp in 1 / 2 cyl will show as rough, but<br />usually oil fouling of plugs is obvious enough<br />that hotter plugs can prolong the time untill<br />rebuild.<br /><br />Sorry I am not more "knowing".<br /><br />My gut is thinking camshaft.

Re: suggestions for next steps? shot rings? time for rebuild?

wildlife.. i share your confusion.<br /><br />all started with an overheat situation.. <br /><br />got that fixed..<br /><br />then the shift cable went bad..<br /><br />got that fixed..<br /><br />then seemed to discover i was running lean.. check fuel flow and it was in fact low pressure.. checked the antisiphon and it was bad.. replaced it.. now the fuel flow to carb is fixed..<br /><br />i apparently over compensated from the lean situation to cause a rich situation.. <br /><br />as a result of the overheat and performance of the engine throughout has not seemed ideal to me.. overheat prompted the comp checks.. low reading on cyl 1 had prompted other check.. like vacuum.. low vacuum reading has prompted other checks like intake leak.. carb gasket leak etc.. <br /><br />and Yes to your point I have no confidence the did the tune up right.. so i intend to do that myself this weekend as well..<br /><br />hotter plugs will compensate for low compression?

Re: suggestions for next steps? shot rings? time for rebuild?

I am begining to see.<br />Hotter plugs with not do anything to compression.<br />Usually when comp drops oil consumption<br />goes up. Excess oil in a cyl will foul the plug.<br />A hotter plug will burn the excess oil. A fouled<br />plug will not burn the cyl charge effectively,<br />hence the cyl does not contribute to the power<br />of the motor. A clean burn is what you want.<br />It is not uncommon for 1 / 2 cyl to need this<br />increase in plug heat. I believe the longer a motor can be used the better. But there is a point were the oil consumption is to great and the motor is done.<br />100 psi in the cyl does not concern me. It will<br />make power if the charge is burned properly.<br /><br />One part frequently over looked is the timing<br />chain. It will give the sym you describe.<br />Is your timing light mark steady? <br />One test is to quickly advance and return the <br />throttle while watching the timing mark.<br />If it "wanders", "bounces", generally not hold<br />steady, then the chain is stretched. I am not talking about the "advance" movement. You can check that at the same time, there are specs<br /> on how much advance at what rpm for this purpose.<br /><br />Timing chains are not expensive and really do<br />give power back.<br /><br /> I am not real good at writing my thoughts.<br /><br />Good luck, let us know what cures you come up with.

Re: suggestions for next steps? shot rings? time for rebuild?

wild<br /><br />hey currently recommeds an AcDelco MR43t sparkplug.. any recommendation for what to move up to in the cylinders in question?<br /><br />thanks