Strange Problem

[MNOBLE]

Hi All, <br />Im having a strange problem with my 1990 mercruiser 260 w/750 hrs. We had the boat on the Ohio river last sunday and it ran great for the first 35 or so miles. I was cruising about 3200 at about 30 mph then it slowly started losing rpm and seemed like it was loading up. I got out of the throttle at which point it immediately stalled and didnt want to start. I managed to get it started at WOT. I threw some ignition parts at it this evening. (didnt do a compression check as i was sure the ignition would fix it) i was wrong. I put on a new cap, rotor, wires, plugs. Timing is on. It feels like its running waaay retarded. A also can hear and feel an interrment click inside the left manifold. I also noticed that for some reason the left manifold it running significantly hotter than the other (to the touch) The engine temp is running a solid 140 degrees. At higher RPM the engine seems fine although i can still hear the interment click from the manifold. I pulled the left valve cover to inspect the valve springs thinking that i may have broken one but they appear fine ( the heads look new ) ( I just bought the boat 2 months ago so im not sure if the heads have been reconditioned ) I have put about 75 hours on it in that time and it has always performed flawlessly. <br />Any ideas or direction would be greatly appreciated. <br />Thank You in advance. <br />Sorry for being so lengthy

 

[Don S]

Re: Strange Problem

Do the compression test ASAP, and check the spark plugs for any indication of water. (Rust, or water dropletes on the spark plug.)

 

[MNOBLE]

Re: Strange Problem

Thanks for the reply Don, I will do the compression tomorrow. As for the plugs, the old plugs came out earlier this evening and looked fine, no fouling, dry and no build up except for #6 which was dry but the tip was deteriorated down to the proceline. (is the Difference in manifold temps normal?)

 

[waterone1@aol.com]

Re: Strange Problem

The compression test would be a good idea. Going in another direction, when I hear someone say that they had to use wide open throttle to start an engine I tend to think of a stuck needle valve or float, causing the carb to dump too much gas into the engine. Crank the engine then remove the flame arrestor and look down the carb throat, if you see puddles of gas, your float or needle valve may be stuck, causing the engine to flood.

 

[MNOBLE]

Re: Strange Problem

Im going to do the carb rebuild tomorrow if i can get it that soon. I will let you know the results.<br /><br />Thanks Mike

 

[MNOBLE]

Re: Strange Problem

Im going to do the carb rebuild tomorrow if i can get it that soon. I will let you know the results.<br /><br />Thanks Mike

 

[rbezdon]

Re: Strange Problem

Also sounds like you may have a water flow problem in one manifold that you should fix before running it again. The hot to the touch issue and the clicking sound are signs of the manifold running WAY too hot. It may be related to the preformance issue too IF that side is over heating it could be damaging someting.

 

[ottawamerc]

Re: Strange Problem

I agree with vatter I too think you have a cooling issue on that side. I would check the manifold and hoses for obstructions, also carefully open the drain petcock on that manifold when the engine is running and check for water flow, careful though it will be very hot!<br /><br />Scott

 

[MNOBLE]

Re: Strange Problem

OK the plan for tonight is to, get a carb kit ordered to help eliminate a fuel problem. Then i will do compression check (will post the results), check for flow on the port side manifold, split the port riser for inspection. <br />Thanks for all your help guys. <br /><br />Mike

 

[prockvoan]

Re: Strange Problem

You didn't say if this was a FWC or raw water cooled.I would pass off the carb rebuild till after a compression test was done.

 

[MNOBLE]

Re: Strange Problem

It is Fresh Water Cooled. Im going to go do the Compression test now. Ill post the results shortly. <br /><br />Thanks<br />Mike

 

[MNOBLE]

Re: Strange Problem

Well the verdict is in and im not a happy camper. Ive got about 120 psi on 1,2,3,4,5,7 but cyl's 6 and 8 (side by side)are stone dead. absolutely no reading dry or wet. So if i apply a bit of logic to this i would have to say that the exhaust manifold that is the hotter is the normal one. Im now thinking that the cooler one is due to the 2 dead cylinders therefore is generating half the heat, that combined with the excess fuel from 6 & 8 helping cool it down. Is it possible to have no compression in those 2 cyls. I would think that a cracked head or blown head gasket would still generate a few PSI on the upstroke. Thoughts are welcome ?<br /><br />Thanks all for helping<br />Mike

 

[flashback]

Re: Strange Problem

severely damaged or stuck valve is the first thing that comes to my mind..guess it's time to pull the head..

 

[prockvoan]

Re: Strange Problem

I would try to pull the valve cover and spend over the engine by hand to check if and which valve is not working.After that,if you can't get it to free or springs bad,time to pull the head.I wouldn't fire up the engine at this time.

 

[rbezdon]

Re: Strange Problem

MN, I think you are right on. Read my last couple of postings. I had exactly the symptoms you have and I found the head gasket burned from 6 to the bolt holt between 6 and 8 and back down to 8. It turns out the center row of bolts winds up in the space between cylinders. I was thinking valve too but it was the gasket. I would think valve if only 1 cylinder was dead, 2 it a gasket. By the way, I had no oil burnig, smoke or water in the oil. Just a clean burn form 6 to bolt to 8. Warning, read the suggestions for removing gaskets and torquing bolts. The old Gaskets on this job are a PAIN to clean off.

 

[rbezdon]

Re: Strange Problem

By the way MN, pull that other riser and manifold while you are in there. I would bet a ton the clicking is from over heating the manifold. Also, if the gasket is gone most of the Pros here on the site told me to pull both heads and replace the gaskets. Not much extra cost but some time (becasue of the da*n old gaskets!! plus a head bolt broke in the block.

 

[ottawamerc]

Re: Strange Problem

Really it's not that big of a job, but definatly follow vatters links!<br /><br />good luck<br />Scott

 

[MNOBLE]

Re: Strange Problem

OK guys, heres the scoop. I got both heads pulled and will be droppped of at the machine shop in the morning. Hopeful to have them back by friday. I split the risers and found nothing remarkable. My concern is that i dont see any point of catastrophic failure on the gasket between the cylinders or the bolts as Vatter said. but then again the gasket came off completely mangled and its hard to see what was going on exactly. The cylinder walls look great, pistons look great, there isnt even a ridge at the cylinder top. Vatter, i also had no oil burnig, smoke or water in the oil. Actually i quite impressed that it ran as well as it did with 2 completely dead cylinders. <br />THanks for all the help guys. Its much appreciated. <br /><br />Mike

 

[MNOBLE]

Re: Strange Problem

One more thing guys, I just went out and inspected the heads a bit more and noticed that the exhause valve on both the dead cylinders are concave from edge to edge. all the other ones are perfectly flat on the bottom except for a 3/4 diameter undercut in the center of the valve. but these two have the same undercut but are also concave all the way to the edge. I have never seen anything like it before. anyone? is it possible for the valve to get bent/pushed up toward into the seat?<br />Mike

 

[Fulltime]

Re: Strange Problem

I had the same problem with my engine (volvo 350). Engine lost power. Did a compresion check and number 3 and 5 had 0 on the gage. I pulled the head and had two sucked valves. Had the heads redone and have run great since.<br />Mike