Mercruiser 3.0 runs strong for 45 minutes then loses power??

[Bszakaly97]

So I have a 2000 sea ray 180 with a mercruiser 3.0 with points ignition. This has been an ongoing problem I’ve been having. I take the boat to the lake warm it up and run it for a couple laps around the lake sometimes more, good power planes out and motor runs very strong and always does for the first 45 minutes or untill I shut it off. Toss and anchor and enjoy myself for an hour or 2 with engine off and everytime I go back to running it she starts good sometimes and other times I have to pump throttle more times then usual to get her started and now my starter makes a strange noise also.. and then it won’t catch plane and I feel like it had 50% of the power it does when I originally get to the lake. Vapor lock? I can still see gas shoot out but maybe not as strong as it normally is? It seems to always happen when I let it sit for a little after running it and it has been high 80s low 90s when it keeps happening. Engines not overheating stays at around 165.. doesn’t necessarily sound like it’s bogging down just a huge loss of power.. any help is appreciated in advance!

 

[Rick Stephens]

I would suggest start with filters. Then hook up a fuel pressure gauge and see what fuel pressure is all the time when running.

 

[Bszakaly97]

I would suggest start with filters. Then hook up a fuel pressure gauge and see what fuel pressure is all the time when running.

I’ve checked filters and fuel pump but like I said it runs great for a while... something to do with running it then letting it sit for a bit. Would a mechanical fuel pump work most of the time but not when hot? When it’s running good it’ll never cut out on me r run incorrectly it’s when I physically shut the engine off for a little after running her hard the problems come into play.

 

[Bszakaly97]

I’ve checked filters and fuel pump but like I said it runs great for a while... something to do with running it then letting it sit for a bit. Would a mechanical fuel pump work most of the time but not when hot? When it’s running good it’ll never cut out on me r run incorrectly it’s when I physically shut the engine off for a little after running her hard the problems come into play.

Maybe put inline fuel gage and check er when the problem starts?

 

[alldodge]

Maybe put inline fuel gage and check er when the problem starts?

Yes
I'm thinking carb problems. A mechanical fuel pump won't work good for a while then start messing up and go back to ok later. Might start flooding

 

[Bt Doctur]

Have you run it on a remote tank?If it runs perfect on the remote I might just have the answer you seek., see my post

 

[Bt Doctur]

 

[Bszakaly97]

Yes
I'm thinking carb problems. A mechanical fuel pump won't work good for a while then start messing up and go back to ok later. Might start flooding

I disagree with the carb issue, I’ve never seen a carb act up only after warming up. I have a spare pump I am possibly try to see if that one does the same thing. Thanks

 

[Bszakaly97]

Have you run it on a remote tank?If it runs perfect on the remote I might just have the answer you seek., see my post

No I haven’t because it runs great for most of the day...maybe I’ll take one with me to use when it acts up

 

[Rick Stephens]

That is a very frustrating problem. Another thing you might try is to take a $12 spark gap tester with you and when it is cranking without firing, plug it in and see if you have spark. If you got a good spark then fuel is most likely issue.

 

[Bszakaly97]

So I have a 2000 sea ray 180 with a mercruiser 3.0 with points ignition. This has been an ongoing problem I’ve been having. I take the boat to the lake warm it up and run it for a couple laps around the lake sometimes more, good power planes out and motor runs very strong and always does for the first 45 minutes or untill I shut it off. Toss and anchor and enjoy myself for an hour or 2 with engine off and everytime I go back to running it she starts good sometimes and other times I have to pump throttle more times then usual to get her started and now my starter makes a strange noise also.. and then it won’t catch plane and I feel like it had 50% of the power it does when I originally get to the lake. Vapor lock? I can still see gas shoot out but maybe not as strong as it normally is? It seems to always happen when I let it sit for a little after running it and it has been high 80s low 90s when it keeps happening. Engines not overheating stays at around 165.. doesn’t necessarily sound like it’s bogging down just a huge loss of power.. any help is appreciated in advance!

I’ve also heard that I’m supposed to have a 1/4 inch gasket from pump to side of engine.. it’s on my spare motor but doesn’t look to be on this one... would that have anything to do with it?

 

[Rick Stephens]

One of the problems I would have answering that is not knowing what motor you are running. A 2000 3.0L Merc would not have points ignition. You never state serial number, and now mention a spare motor. What motor are we talking about here?

 

[Bszakaly97]

One of the problems I would have answering that is not knowing what motor you are running. A 2000 3.0L Merc would not have points ignition. You never state serial number, and now mention a spare motor. What motor are we talking about here?

My apologies, don’t have serial number on me... bought the boat with a motor with a cracked block and a whole lotta water intrusion, pulled motor and swapped in a older mode with points.

 

[Rick Stephens]

My apologies, don’t have serial number on me... bought the boat with a motor with a cracked block and a whole lotta water intrusion, pulled motor and swapped in a older mode with points.

Switch all the newer ignition stuff to that motor!

 

[Bszakaly97]

Switch all the newer ignition stuff to that motor!

Yes was planning on doing that during the winter( plan on going through entire motor anyways) I think I’m going to try putting a shut off valve on gas line and run it all day and let it manually run out of gas in my line when I shut er off for a while. Atleast then I can see if I’m having a vapor lock problem in the fuel line.

 

[Rick Stephens]

Generally speaking, boats don't have vapor locks. That would be my last thought for a cause.