2nd motor in 9 hours...spun crank bearing?

[foothill]

I have a 1976 Sea Rey Sports Bridge with twin 350 Chevy, Mercruiser motors. I just had a shop rebuild the Port and Starboard motors. <br /><br />The shop that did the work is a big shop that not only does there own work but also supplies motors for many other engine resellers. This is a large remanufactured engine shop that primarily rebuilds automotive/truck motors but also does work on marine engins.<br /><br />I have no problems with the Port motor (standard rotation) and it has run perfect for 9.2 hours. The rebuilt Starboard motor (reverse rotation) blew up after just 5.7 hours. The shop said it was due to it getting too hot but it sounded to me like it spun a crank bearing (a low knock from the bottom of the motor). The heat tabs on the freeze plugs and heads were not melted off which indicated the motor did not get too hot. <br /><br />After just 3.5 hours on the 2nd rebuilt motor the low knock from the crank area is starting to come back! I have varied the speed/rpm of the motor and never ran it at WOT. Moreover, I never ran the motor at one speed for more than a minute or so (other than a low speed idol in the 5-mph zone). I tried to break both rebuilt motors in slowly and per the builder’s instructions.<br /><br />The 1st Starboard motor was warranted by the builder with out any problem. When I told them about the second motor they said to bring it in and they would fix it. That’s great but I have to remove it and replace it at my own cost and inconvenience once again. Time and money I really don’t have to waste if it’s just going to blow up again. <br /><br />Why could this be happening? The shop manager says they are using marine parts (freeze plugs and gaskets) and a counter rotating Camshaft and gear. Supposedly the only difference in cw and ccw motors.<br /><br />The motors run cool and have clean full oil levels. I have been checking the temperature with a heat gun in numerous places. The temperature never gets above 135 degrees anywhere on the engine. I have new water pumps and exhaust manifolds, for that matter, I have installed just about new everything. <br /><br />Is it just a coincidence that two reverse rotation motors blew up with less than 4 hours on them while the standard rotation Port motor is running great? Or, could the builder possibly be doing something wrong with the assembly?<br /><br />Any ideas or suggestions would be appreciated!<br /><br />Thanks, Bob

 

[Bt Doctur]

Re: 2nd motor in 9 hours...spun crank bearing?

did you "pre-lube " the motors BEFORE you ran them.If theres an air pocket,the bearing can be dry for a bit.leading cause of spun bearings.just using oil at assembly leaves the oil galleries dry on startup.best way is to get an old dist. (car unit ok),remove the drive gear, install and use a drill to pre-oil untill you see oil come up to the rockers.never lost a motor using this method.

 

[Northern Eclipse]

Re: 2nd motor in 9 hours...spun crank bearing?

It seems that there is a good chance the builder is doing something wrong, if the motor is turning bearings then there is a clearance issue or a oiling issue. I not sure if counter rotating motor's require the crank to be drilled the same or not for oil holes but I think they might since those holes are chambered. What is the oil pressure reading for that motor? and is it steady?.

 

[Buttanic]

Re: 2nd motor in 9 hours...spun crank bearing?

I am not sure but it would seem that a reverse rotation motor would require a different oil pump. Spun bearings are usually the result of lack of oil. Which bearing was spun in the first engine.

 

[foothill]

Re: 2nd motor in 9 hours...spun crank bearing?

Oil pressure could be an issue and I’m not sure what bearing was spun on the 1st motor. All I could get from the shop manager is that it appeared the motor got too hot somehow and blew up. Possibly a cracked block...blah…blah…blah. Don’t worry we will fix it at no charge.<br /><br />More information:<br /><br />At idol, both motors read the same oil pressure, apprx 40 on a gauge that reads from 0 to 80. This is where it ran at the dock for the first hour. Just idol and short revving of the motor to less than 3k rpms. The pressure would increase slightly on the revving. <br /><br />Hour number 2 on the motor consisted of motoring out to the breakwater and short acceleration periods to 3k or less rpms. I noticed the pressure staying the same on both motors for the most part. When I accelerated from 2500 rpm to 3000 the starboard pressure went to 80 and fluctuated to completely pegged and 80. I throttled down to idol and the gauge stayed at 80 or pegged. I shut down the motor and called the shop on my cell phone.<br /><br />I was told not to worry about high oil pressure. They weren’t sure what the cause was but it could be a bad gauge or maybe the valve which the oil filter screws into is malfunctioning (can’t remember the name I was told for this part). Anyway it was not an emergency and I could check that part the next time I changed the oil filter, it’s only 2 bolts holding on the plate under the filter.<br /><br />Ok I guess.<br /><br />Anyway I motored back to my slip and started to flush the motors with fresh water. The gauge acted intermittently with showing the same approx pressure as the port motor and 80 or pegged. <br /><br />When I came back the next week the gauge still showed 80 with just the key on and the motor off. When I started the motor it went down to match the port at about 40. During hour 3 of running the same thing happened as hour two with the high oil pressure. This time I didn’t think anything about it and just keep varying the rpm of the motor trying to ease it back into service with a proper break in.<br /><br />Didn’t hear anything unusual with the engine. However, when I brought it back to the slip and during the flushing of the motor with fresh water I could hear a knock that got more pronounced when the rpms increased.<br /><br />Of course I shut it off and call the shop…that’s were I am today. Can high oil pressure hurt the motor?<br /><br /><br />What do you think about this statement that I read on another site?<br /><br />Two of the most inportant things on revesing and engine putting the pistons in 180 from normal. The wrist pins are slightly off center to make for the side loading at the top of the power stroke. The other thing is if you have the old style rear main seal you need one for reverse rotation.

 

[Buttanic]

Re: 2nd motor in 9 hours...spun crank bearing?

The piston pins are off set but this would not cause a problem. A lot of race engines are built with the pin off set the opposite way. Don't know about a different rear seal.