mercruiser 470 stalls going into gear when hot

[merc 470]

Re: mercruiser 470 stalls going into gear when hot

Yes I still Own the Boat But it is in the back yard right now. Its still cold up here in new hampshire. I did find a couple of not tight intake manifold bolts when it was winterized. This spring I plan to pull the intake and check for a hairline crack in manifold and also check for warpage of the intake to head surface, install a new intake gasket, clean all threads and use loctite. In speaking with the previous owner the motor has been run hot (180-200F) before I replaced the rubber impeller.

 

[mcwinfrey8]

Re: mercruiser 470 stalls going into gear when hot

I'd be interested to find out what the problem is, as my 470 is doing exactly the same! runs sweet as a nut until it gets warmed right up then begins the odd misfire and dies like fuel starvation when you apply throttle unless youbuild it up gradually. Been through the carb enough times to do it blindfolded, and always clean and full! Annoying!

 

[Haut Medoc]

Re: mercruiser 470 stalls going into gear when hot

It does sound like a bad coil, they act funny when they on their way out & get hot.....JK

 

[merc 470]

Re: mercruiser 470 stalls going into gear when hot

I'm leaning towards an intake leak when it's hot (run 3/4 throttle for 20-25 minutes. I wont't know for certain until I pull the intake and check for crack or warped sealing surface against head. (new coil, carb, fuel pump, pts & condenser, impeller, engine compartment has extra venting and fuel line cooler has been installed, and distributor was regrounded with new wire) Most every thing has been gone through already, except warpage and crack check on intake manifold when intake gasket was replaced last year. Short runs are ok, problem only happens when engine is run for 20-25 minuute cruise at 3/4 throttle. I won't be working on it for a few more weeks, but will keep you posted as to what I find. I'd also be glad to hear of any other suggestions that I should be checking for. NOTE: it will run fine all day long at 3/4 throttle, problem is only there after a short shut down after long cruise.

 

[hullofalottatrouble]

Re: mercruiser 470 stalls going into gear when hot

merc470 you done any compression? vacuum? leak down test? please do post what you find.. i think i have a similar problem..

 

[merc 470]

Re: mercruiser 470 stalls going into gear when hot

I think I found the problem. Intake manifold was pulled last week. I found two problems. #1-Intake manifold was warped (no cracks). Machine shop took 0.030" off face to get it flat. #2-Block to cylinder head seam is not flat. The block at either end of head is flat to provide good seal for intake but in the center it bows outward. This area will need to be sanded or ground down carefully <br />Because the intake manifold is bolted both to the block and head, the block and the warped manifold were keeping the #2 and #3 cylinders from getting a good tight seal at intake gasket. The intake leak is not external but is sucking hot oil vapors from the crankcase through the oil ports in the heads.<br />I'm pretty sure that this is what happening. The way that everything is warped would suggest a very poor seal (if at all) for the gasket about dead center of manifold on the bottom half. Right between #2 and #3 cylinder intakes.<br />Boat won't be back on water for another few weeks. I will let you know how it goes.

 

[michael-lagrange]

Re: mercruiser 470 stalls going into gear when hot

a compression test on all cylinders- one cold,one while at operating temp will help you determine head or cylinder problems. i strongly suggest that test before you spend money on a ifey problem.

 

[merc 470]

Re: mercruiser 470 stalls going into gear when hot

I had boat out twice<br />First time about 65 degrees out, no problems.<br />Second time about 85 degrees, no problems.<br />I think it is fixed.