Hello everyone.
Need some help again. Now it is overheating, burning exhaust boots, and continuing to prove it may just be possessed.
I wanted to include the original threads on this repower as I can not update an old thread (and it seems everything is archived now), and I thought I would start a new thread as I have found more problems etc.
So this is sort of an update to an update lol.
Link to the original http://www.marineengine.com/cgi-bin/discus/show.cgi?12486/84984
Link to first update http://www.marineengine.com/boat-forum/showthread.php?378705-Problems-with-rebuilt-7.4-running-poorly-and-valve-taps-HELP!!-%28from-the-archives%29
One Last Problem!
Hope this collection of info will be helpful to others, and maybe help someone avoid the horrors I have had to. There is nothing I can compare this to, and after 6 years I have to believe this is in the running for the worlds longest repower.
You all have been a big help, and thanks are again due.
The newest problem involves over heating, but first a little history.
The previous thread left off with a vibration problem (for those not familiar with the old threads almost everything that could possibly go wrong pretty much has) and so far that was the last major engine issue.
After getting put off to the end of the list for my new mechanic to get to pulling the engine again so it could be inspected (nearly a year, but thats not so bad compared to the previous issues lol) we finally pulled the flywheel and it was found to be installed off one bolt, and also the cause of the vibration.
So anyone with a gen IV 7.4 454 be advised if repowering to tell your installer that the flywheel does indeed need to put on in the correct position as intended by GM even though Mercruiser does remove the dowel pin from the crank shaft (sometimes, but after numerous calls it seems that they are not exactly sure of they remove or leave the pin either) it must be installed as if the pin was there, and it is not an anything goes just put it on in any position scenario as it may be on others (fords, sb gm etc)
Since we had a new coupler on hand just in case the old one was the problem it did get a new coupler installed as well (I hope the new steel one holds up as well and long as the previous aluminum one) and now pretty much everything has been rebuilt, repaired, or replaced in the whole drive system on this boat.
The only thing that is original now is the transom assembly, and would you believe after all of this that this may actually be a problem.
After a long sigh of relief that the vibration problem was corrected and launching the boat to find that though it finally runs right and without problem (what a grin I must have had on my face when it was finally running good after all this BS and time) but now that it does run well it can also rev up to normal cruising rpm's and as the revs go up so does the temp.
On the first time out from the initial launch it was not too bad and only hit the mid way point or line between 245f and 220f (not exactly sure what that means to actual temp, but I figured around 175-180f as that splits the diff etc) on the orig SeaRay gauge running at 3200 rpm. On the next trip of about 20 miles each way did not make the full trip without help from a tow.
On the way out it ran mostly at 3200 as it was a bit rough and was not in any real hurry and all was well at the above temps, but as it calmed down a bit I had increased speed somewhat (approx 3800 to 4200 rpm) and the temps rose, but even though it never actually overheated and only got halfway between the mark it was running at 3200 and 220f point (would 190-200 be a good guess?) and was still running very well and smooth in an instant there was the smell of burning rubber that was immediately followed by smoke coming from the engine cover (seat).
After a quick shut down I found that the port exhaust must have overheated big time as it was burning/melting the exhaust boot between the riser/elbow and the downward elbow that attaches to the y-pipe. Running at idle did cool things down quickly to 145f or normal running temp, but after this even running at 2800 - 3200 rpm would send the temp gauge back up to the 200f range so I got her towed in. Since I have a bridge restriction to deal with and the tower not being able to fit under etc I did decide to just idle the last half mile or so, and it ran cool and without additional problem.
Wow does this ever end
After tearing the exhaust down and closer inspection it melted the boot enough to need replacing (it would leak etc) and the butterfly type exhaust flapper was not to be found. The flappers were new during the last go around so it should have been there. I had originally thought that possibly the one thing I did not have involvement with had gone wrong as I was outside the boat as the engine was initially lowered onto the exhaust and maybe the flapper fell inside the y-pipe and was restricting exhaust flow etc. I was able to fish out one of the steel flanges that are coated in rubber with a wire hanger, and assumed that the plastic parts just melted and flowed out the exhaust, and hopefully the other steel flange managed to get out and the replacement would end my problem, but well that just did not work out (I dont seem to get any lucky breaks lol)
Since I was directed to check the flow coming into the main hose leading to the engine mounted raw water pump I did find the most likely cause quickly as the flow sitting at the dock was similar to a half turned on water hose.
This is where things get confusing to me as I have been told completely conflicting information on how to correct this loss of flow on the raw water intake.
The local auth Merc dealer (who was also the guy who got the flywheel issue right sight unseen) who is my main parts supplier seems to feel that attempting to repair the small intake hose that is connecting the drive to or through the transom will most likely not work on this 89 bravo transom assembly, and that I need to set up a through hull system like used on true inboards, or even one similar to the TRS drives etc, but my mechanic believes we can just replace that hose without issue.
My question for you all is what do you think on this, and what information can you offer on the pro's and con's of the thru hull set up compared to the thru the drive pick up?
The mechanic really means well, but I have had to slow him down some on some of the "extra" parts purchases he suggests as this is just getting crazy and I really do not want to use the parts replacement diagnosis system anymore
Why spend another $50 on hoses and grommets if I am going to have to haul it and install a through hull intake? Is the hose replaceable or?
I have already tried to back flush it, and checked the cooler for any impeller pieces just in case, but the cooler was clear, and the flush did not work. I even fished a smaller round brush through the transom (where the main raw water hose attaches) to see if I could remove something that may be blocking the intake, but that did little to help and it seems the hose is most likely the culprit.
Any thoughts and ideas are welcome as I refuse to lose another season, and there is no way I can idle around all year at $4 a gallon lol
Need some help again. Now it is overheating, burning exhaust boots, and continuing to prove it may just be possessed.
I wanted to include the original threads on this repower as I can not update an old thread (and it seems everything is archived now), and I thought I would start a new thread as I have found more problems etc.
So this is sort of an update to an update lol.
Link to the original http://www.marineengine.com/cgi-bin/discus/show.cgi?12486/84984
Link to first update http://www.marineengine.com/boat-forum/showthread.php?378705-Problems-with-rebuilt-7.4-running-poorly-and-valve-taps-HELP!!-%28from-the-archives%29
One Last Problem!
Hope this collection of info will be helpful to others, and maybe help someone avoid the horrors I have had to. There is nothing I can compare this to, and after 6 years I have to believe this is in the running for the worlds longest repower.
You all have been a big help, and thanks are again due.
The newest problem involves over heating, but first a little history.
The previous thread left off with a vibration problem (for those not familiar with the old threads almost everything that could possibly go wrong pretty much has) and so far that was the last major engine issue.
After getting put off to the end of the list for my new mechanic to get to pulling the engine again so it could be inspected (nearly a year, but thats not so bad compared to the previous issues lol) we finally pulled the flywheel and it was found to be installed off one bolt, and also the cause of the vibration.
So anyone with a gen IV 7.4 454 be advised if repowering to tell your installer that the flywheel does indeed need to put on in the correct position as intended by GM even though Mercruiser does remove the dowel pin from the crank shaft (sometimes, but after numerous calls it seems that they are not exactly sure of they remove or leave the pin either) it must be installed as if the pin was there, and it is not an anything goes just put it on in any position scenario as it may be on others (fords, sb gm etc)
Since we had a new coupler on hand just in case the old one was the problem it did get a new coupler installed as well (I hope the new steel one holds up as well and long as the previous aluminum one) and now pretty much everything has been rebuilt, repaired, or replaced in the whole drive system on this boat.
The only thing that is original now is the transom assembly, and would you believe after all of this that this may actually be a problem.
After a long sigh of relief that the vibration problem was corrected and launching the boat to find that though it finally runs right and without problem (what a grin I must have had on my face when it was finally running good after all this BS and time) but now that it does run well it can also rev up to normal cruising rpm's and as the revs go up so does the temp.
On the first time out from the initial launch it was not too bad and only hit the mid way point or line between 245f and 220f (not exactly sure what that means to actual temp, but I figured around 175-180f as that splits the diff etc) on the orig SeaRay gauge running at 3200 rpm. On the next trip of about 20 miles each way did not make the full trip without help from a tow.
On the way out it ran mostly at 3200 as it was a bit rough and was not in any real hurry and all was well at the above temps, but as it calmed down a bit I had increased speed somewhat (approx 3800 to 4200 rpm) and the temps rose, but even though it never actually overheated and only got halfway between the mark it was running at 3200 and 220f point (would 190-200 be a good guess?) and was still running very well and smooth in an instant there was the smell of burning rubber that was immediately followed by smoke coming from the engine cover (seat).
After a quick shut down I found that the port exhaust must have overheated big time as it was burning/melting the exhaust boot between the riser/elbow and the downward elbow that attaches to the y-pipe. Running at idle did cool things down quickly to 145f or normal running temp, but after this even running at 2800 - 3200 rpm would send the temp gauge back up to the 200f range so I got her towed in. Since I have a bridge restriction to deal with and the tower not being able to fit under etc I did decide to just idle the last half mile or so, and it ran cool and without additional problem.
Wow does this ever end
After tearing the exhaust down and closer inspection it melted the boot enough to need replacing (it would leak etc) and the butterfly type exhaust flapper was not to be found. The flappers were new during the last go around so it should have been there. I had originally thought that possibly the one thing I did not have involvement with had gone wrong as I was outside the boat as the engine was initially lowered onto the exhaust and maybe the flapper fell inside the y-pipe and was restricting exhaust flow etc. I was able to fish out one of the steel flanges that are coated in rubber with a wire hanger, and assumed that the plastic parts just melted and flowed out the exhaust, and hopefully the other steel flange managed to get out and the replacement would end my problem, but well that just did not work out (I dont seem to get any lucky breaks lol)
Since I was directed to check the flow coming into the main hose leading to the engine mounted raw water pump I did find the most likely cause quickly as the flow sitting at the dock was similar to a half turned on water hose.
This is where things get confusing to me as I have been told completely conflicting information on how to correct this loss of flow on the raw water intake.
The local auth Merc dealer (who was also the guy who got the flywheel issue right sight unseen) who is my main parts supplier seems to feel that attempting to repair the small intake hose that is connecting the drive to or through the transom will most likely not work on this 89 bravo transom assembly, and that I need to set up a through hull system like used on true inboards, or even one similar to the TRS drives etc, but my mechanic believes we can just replace that hose without issue.
My question for you all is what do you think on this, and what information can you offer on the pro's and con's of the thru hull set up compared to the thru the drive pick up?
The mechanic really means well, but I have had to slow him down some on some of the "extra" parts purchases he suggests as this is just getting crazy and I really do not want to use the parts replacement diagnosis system anymore
Why spend another $50 on hoses and grommets if I am going to have to haul it and install a through hull intake? Is the hose replaceable or?
I have already tried to back flush it, and checked the cooler for any impeller pieces just in case, but the cooler was clear, and the flush did not work. I even fished a smaller round brush through the transom (where the main raw water hose attaches) to see if I could remove something that may be blocking the intake, but that did little to help and it seems the hose is most likely the culprit.
Any thoughts and ideas are welcome as I refuse to lose another season, and there is no way I can idle around all year at $4 a gallon lol
