OMC 3.0L won't prime unless rpm is high

[tic]

Well, the easy "fix" for my continuing problem.( water temp. rises rapidly after first start, almost pegs, shut off boat, let cool, restart and temps are normal, and no problems the rest of the day with numerous restarts).. If when we first start the boat we run the rpm's up to about 2,000 the system gets water and all is good.. I just hate running a cold engine that fast..If we let it idle after the first start of the day, the water temp keeps climbing until we have to shut it off... New impeller kit and new thermostat kit installed.. It just doesn't want to prime on the first start..

 

[sea wolf]

Re: OMC 3.0L won't prime unless rpm is high

Pull hose to t stat, check for blockage, make sure hose isn't collapsing. How old is it? Make sure vent hole in pump housing isn't plugged. Check plastic housing for hairline cracks. If pump is sucking air, pump won't perform properly. Did a new metal plate come with the impeller kit? If not, replace it. You better find out what's wrong. Keep overheating that engine, & you'll be looking for a new block.

 

[cooter2506]

Re: OMC 3.0L won't prime unless rpm is high

My father in law has a 4.3 OMC that does the same thing. How old are the Risers. He has to clear his out by shutting it down and blowing it out the exhaust which sounds exacly like you are doing. His risers are deteriorating but doesnt want to spend the $1000 to replace them.

 

[tic]

Re: OMC 3.0L won't prime unless rpm is high

1988... vent hole is clear and it's a new plastic housing and metal plate for the impeller (complete kit). Input hose to T-stat was pulled and checked, hose isn't collapsing and water runs freely out the house w/ engine running at low rpm. (new T-stat kit too) All original exhaust parts... Yep, riser might be going south, and or manifold.. Didn't think of that.. I'm not ready to drop 1,000 bucks on new exhaust either... Engine already has two cracks in the block which have been repaired.. No water in the oil or the cylinders and we are looking at buying a new boat so I'll just nurse this one along as best I can.. It's a shame because the rest of the boat is cherry.. SOMEBODY didn't winterize it once, or twice, or ever for all I know. How do you sell a boat with a cracked engine block?... I would never try to hide that information but is the boat worth anything in this condition?... It will run at 4550 rpm all day, sounds great too.. Doesn't use any oil etc. etc... No wood rot (that I'm aware of), seats, upholstery all look new.. Hull is in great shape too... Here's a pic..