weird overheat problem

[hullofalottatrouble]

this will be long but want to give as much detail as possible.. <br /><br />have a 1982 mercruiser 260 with I-drive <br /><br />had boat out a few weeks back ran fine for 1-2 hours then started to overheat.. or at least thats the way i remember it..<br /><br />took it out next day to check on things and ran hot again.. while it was out the shift cable gave out.. wouldnt engage into forward.. finally got it to engage and engine was running really rough.. stalled when throttled up or down.. ran enough to get back to ramp and stalled when throttle down at ramp.. <br /><br />took boat to shop.. they said bought ran fine for 1 hr on trailer and hose and didnt see any over heat problem.. did a tune up and replaced a water hose.. also mentioned there was no thermostat.. <br /><br />i replaced the shift cable.. took boat out again and under load as I was moving out of the harbor heat started to slowly creep up.. temp got to about 210 as the temp crept up the engine labored and felt like it was missing and stalled.. drifted around to let engine cool.. start again.. soon as it got into gear it died.. tried a few times did the same thing.. engine was about 190.. when engine got back down to 160 again.. started right up.. went into gear ran fine.. engine got hot again 210 ish again slowly started to labor and stalled.. got towed into ramp.. <br /><br />engine heats up to 160 at idle when on ramp and stays there at idle.. <br /><br />is this a water pump/impeller issue or possible a more serious engine problem? <br /><br />Thanks <br />Rob

 

[rbezdon]

Re: weird overheat problem

To be honest, it sounds to me that at this point you may have something more serious than just an impeller but you may have that also. The fact that the engine starts running normaly at 160 and gets progressively worse as the temp increases a little or it runs longer sort of sounds like a head gasket to me. Do some fairly simple diagnostics (look for water in the oil, compression tests, check color of plugs etc.) My guess is you may have the impeller issue and that is what started the other by running too hot in the first place. By the way, get a new shop. A bad impeller in the lower unit can many times be overcome by the pressure from the muff's water supply and the boat runs forever on the muffs cool as can be (I had this). Put it in the water and problem is back. This is because in the water all the water supply must be "sucked" up by the impeller, not pushed up by the hose water pressure. If I took my boat to a repair house, told them I have an overheating problem and all the checking they did was on the hose, I'd get a new mechanic. At least alert them to this site and maybe they can learn from the experts here. This is a very common problem and there are many threads in this issue here.

 

[hullofalottatrouble]

Re: weird overheat problem

Ron,<br /><br />Thanks for the feedback.<br /><br />If it is a bad gasket can I just replace it at this point are is it possibly going to need a rebuild? Rather new to boat engine and maintenance just trying to set expectations for myself here. <br /><br />Thanks,<br />Rob

 

[rbezdon]

Re: weird overheat problem

Since the engine has not been fully diagnosed through testing and torn down to asses all the damage, you just can not tell yet. It also depends on how many hours and general wear and tear it has seen. I do not think anyone can tell you 100% what all the issues are yet with out more testing and actually seeing the engine torn down. Sorry. Also, it depends on how much of the work you can do and your budget. I am sure you could get a crate engine out of stock some where, air freight it in and swap it very easy but VERY expensively. A streight engine swap with a known good engine is the fastest and maybe the easiest way you garantee to fix all that might be wrong. Nest time I suggest you keep a careful eye on the gages and shut down completely when the temp goes any higher than its "normal" point and you will likely eliminate all of this. No such thing as trying to make it back to the dock with an overheated engine and not do more damage.

 

[hullofalottatrouble]

Re: weird overheat problem

to be clear i did not run it into the red.. thou admittedly it was operating and very slow speeds at temps above normal.. when running at normal temp the thing runs very well.. not a burp or a hiccup involved.. i will certainly hope for the best.. <br /><br />thanks for your feedback.. i appreciate it...

 

[hullofalottatrouble]

Re: weird overheat problem

as far as the overheat problem.. is it safe to run it on the hose and just pull some of the internal water hoses to see where there might be a restriction? what are some steps to take here.. it will start with the impeller but it was just replaced in april..

 

[rbezdon]

Re: weird overheat problem

I remember reading another thread on this. I think one of the main guys around here suggested what you are proposing, pulliing certain hoses for short times to see water flow. The only thing is that the hose and muffs can mask lower unit problems. The water pressure from the hose can force water in when there is not enough suction to pull it up, especially at lower RPM on the muffs. I had this issue before, idle fine on muffs over heat at idle in gear in the water. On the other hand, you should be able to see water flow through the system inside the boat OK. Be careful, water is hot and you are likely to get wet!!. I have also read several threads where clear hoses get subbed (temporarily for the regular ones to look for air bubbles in the water flow. Search around this site, there is a TON of information on this topic!! Lots of great minds here put their ideas in writing.

 

[hullofalottatrouble]

Re: weird overheat problem

vatter,<br /><br />thanks for the feedback an info.<br /><br />One question. I caught on another thread that a blown head gasket could be the cause of an overheat problem? Does that make sense?

 

[hullofalottatrouble]

Re: weird overheat problem

okay so the blown head could contribute/cause the overheat problem? but then what caused the blown gasket?

 

[tommays]

Re: weird overheat problem

flap<br /> http://mercstuff.com/drive_idalpha.htm <br /><br /> http://mercstuff.com/drive_id.htm <br /><br />whats and I-drive<br /><br />how old is that water pump and who instaled it because it sounds like you big problem is water flow<br /><br />there are also a lot of places between the pump and the motor that can block flow<br /><br />and are you in fresh water or salt and how old are your maifold/risers<br /><br />tommays

 

[hullofalottatrouble]

Re: weird overheat problem

its a 260 drive on a Merc 260 engine.. made in 1982.. not sure why i called it an I drive.. typo work sumptin who knows..<br /><br />the impeller is from april.. water pump i dont know.. it is fresh water.. the manifold/risers are both relatively new..

 

[hullofalottatrouble]

Re: weird overheat problem

did compression test<br /><br />125<br />100<br />125<br />125<br />125<br />125<br />140<br />140<br /><br />looks like 100 got a problem there but it is still within acceptable range??

 

[Dunaruna]

Re: weird overheat problem

No. It's enough to run reasonable - maybe, but it's low enough to need further investigation.<br /><br />To answer your question of a few posts ago - a blown head gasket is usually caused by overheating, often it will blow between two cylinders (but not always) which causes low comps on those two cyls.<br /><br />The 140psi comps also standout. Do the test again and this time include the cylinder # next to the reading. Use a very good battery and hold the intake open.<br /><br />Aldo

 

[hullofalottatrouble]

Re: weird overheat problem

thanks for the feedback.. <br /><br />what do the high comp cylinders indicate? low comp i get .. but do the high comp also indicate a problem with those 2?

 

[Dunaruna]

Re: weird overheat problem

140 is not too high, it's the other six readings that are too low!<br /><br />I suggest you do it again as I described, just to be sure and accurate. You can also follow up with a 'wet' comp test.<br /><br />Aldo

 

[hullofalottatrouble]

Re: weird overheat problem

i have to admit the test was done cold and battery probably wasnt the highest charged battery around..<br /><br />in any event the overheat problem was cause by a clogged water tube in the upper.. there was a old dried up torn up seal that holds the water tube in the upper that was actually cloggin the tube.. <br /><br />so overheat problem solved..