last ride problems

[grinder]

hi all. i have a 91 convincer 251 gtx with a 502 mag.our last ride for the year was great until the end of the day when i started to hear what sounded like lifter noise. the motor made a "pop" and then sounded like i dropped a cylinder. im thinking maybe a valve spring, but not sure. our local engine builder, which has a great reputation said he will completly rebuild my engine for $2200 to $2600. the motor has 700 well cared for hours, and im thinking about having it done just to start fresh. i would really appreciate any feedback as to any ideas you all have on the rebuild idea. thanks

 

[PapaMaC]

A rebuild wouldn't be a bad idea, but if he can diagnose the real problem then you can see if the rebuild is really necessary.

 

[Big Red]

I would say you got your money's worth out of that engine. 700 hours on a big block is a lot of hours in a heavy boat like a 91 251 GTX

Maintenance was a key factor here. I would just wait till the engine is pulled apart and see what happened, or if any major parts were destroyed.

 

[dogschool]

I agree with Red, 700 hrs is alot! I just went thru the same
thing earlier this year and my 454 mag had just under 500 hrs.
and I run my boat pretty hard, so you got pretty good life out
of your motor I'd say!

 

[Big Red]

I asked several boat people that have been in the boat biz a long time about hours on a engine when I was looking to buy. And they told me that 400 hours on a BB in a big boat like a Convincor or ZT you could consider the engine tired and if it had boost it was a ticking time bomb with 400 hours.

The most I have seen was 610 on a Convincor with the orginal 454

 

[grinder]

well i guess ive done pretty well then logging 700 hours on the original 502. ive been on a lot of performance boats, and the wife and i agree that in a 25 foot boat, we havn't found a better ride. i dont want to sound modest but every where we boat, we get a lot of comments on how nice our boat is! we spend a lot of time cleaning and maintaining this rig and its nice to hear people say,"is that new? then i answer, no, its 17 years old! it's pretty impressive that an old checkmate still turns heads pics to follow

 

[winter]

I agree with all the above as well. I spent a good deal of time talking to people about rebuilding the engine in the 202 Persuader I'm trying to sell (rebuild only for more power) and first and foremost you need to find a builder who understands the difference between a car motor and marine motor. Basically, they need to understand that a Marine motor needs gobs of low end torque and will be under load all the time. Good luck, hope all goes well!

 

[rhmapes]

I would give serious consideration to converting your engine to a roller cam while you are having it rebuilt. You have probably wiped the flat cam out. This is a growing problem since most oils have reduced the amount of zinc in thier oils. Hope this helps you.

 

[ezstriper]

1st depends on how it was run and maintained...I ran my original 454's in my gibson over 1000 hours, still would have been running today I suspect if not for a major storm and wave up the exhaust hydro locked them both while running at 1500 rpm...insurance replaced both...I tore them down and other that the water...they lookes as if they had 200 hrs on them. now they never saw over 4000 rpm and lived mainly at 3200, ran royal purple oil since about 300 hrs. but back to yours find out what failed..but I would go thru the engine or replace at this point...Rob