180rpm

[Navyaj]

I have a 1996 454 7.4L bravo 2. Engine rebuilt last year. Took boat out last weekend. It wouldnt go above 1600rpm full throttle. We limped around lake. Even got new gas a marina on top of the 20 gallons i put in before we got there. Also the engine starts fine each time. Rough but starts. Would die when put in gear. Barely made back to ramp. No over heating or low oil pressure.

My first thought was fuel issue. So we bought a filter next day. Not fix. I pulled the mechanical pump this weekend and checked diaphragm. Good. Pulled water pump. Good

Now im scratching my head. This old 454 doesn't have limp mode, i dont think???

What else can cause this. We didnt hit anything. 2 weeks ago. Ran perfect. Last week….not so perfect.
Dont think bad gas because i filled up my truck with same gas too.
Havent checked fuel pressure because fuel line from pump to carburetor is a metal pipe.

Thoughts? Does it have a limp mode?

 

[tpenfield]

Carbureted engine would not be a 'limp mode' thing (fuel injected only)

Has the distributor moved off of its proper timing setting? Getting spark on all cylinders? You could try a compression test.

Got a serial number of the engine?

 

[nola mike]

Carbureted engine would not be a 'limp mode' thing (fuel injected only)

Sure it does... Just put some debris or water in there

Did you check the contents of your old filter?
New gas +bad gas =more bad gas. All the water/crud hangs out at the bottom of your tank. Would check all that Ted mentioned, but usually it's bad gas/carb until proven otherwise. Can try running off of a Jerry can

 

[garbageguy]

anti-siphon valve bad?

 

[Navyaj]

Well we tried again after putting pump back together and priming gas line. It started went yo 3k rmp with prop engaged just fine. So we took it to lake. But in water. A bang. Back to same problem. 1600-1800rpm max. Rough running, dying when put into gear. Disengaged prop, and engine goes to 3k. Reengage prop and 1600 max if it will run at all. Basically pulled off trailer. Turned around put back on trailor.
It ran great in my driveway. But under water load. Not at all.