inboard motor problems

[tlr426]

Hi all.

This is a problem with my dads boat and I have little info on the exact egine specs. But here it goes the egine is a 454 with a single carb. The boat motor was a new install shortblock by a bum mechanic... The motor starts and runs at idle fine. When you try to get onto plane it revs up but lacks power and has a bit of a surge and sputter to it. I think it is fuel but not sure. From the tank the fuel line is 3/8 into the water sep filtter then the out goes to the carb with a 1/4 hard line.... Why so small, why is it a hard line? The line has bad bends that deffinatly restrict the flow. Also of the carb there is a vacume line that goes back to what looks like a low preasure pump. It there a high presure pump some place. Any help or ideas would be helpful. I say it should be a warrenty item ... But the guy that installed it is usless so I want to give it a go first. Thanks all

[Bada Bing]

I would put a new fuel line on it. If it has a mechanical pump it would be on the lower front of the engine starboard side. I would also run only non ethanol fuel.

[Chas0218]

Is there anything on the carb telling you what brand it is?

 

Throw a fuel pressure gauge on the line when you replace it and see how much pressure you're building.  It should be 7-10lbs. more than that it will blow past the needle and seat any less it could be starving the motor for fuel.  I would also replace the cap and rotor while you're at it.  Just remembered you should also make sure the boat is level and check the floats are adjusted properly.

 

A lot of times when a mechanical fuel pump goes bad it lets fuel back into the engine.  I would check to see if the oil smells like un-burnt fuel. You should be able to tell with just the little bit on the dipstick.

 

If it is surging that generally means it is running lean.  Pull the number 1 plug and see what color it is do this right after you try to get on plane. Rev it up to highest rpm possible and shut her down immediately that will give you the best idea of whats going on mixture wise.

 

Also double check the timing.  I bought an old GM that was running like that and the timing was very retarded (no pun intended).

Edited June 17, 2014 by Chas0218

[tlr426]

When I replace the fule line should I match the size? Or should I bump it up to 3/8 flexable line? It seems way to small?

[Robert Piette]

Hi,

 

I had a similar problem. Found out after checking everything that the mechanic had  put the new spark plug wires in the wrong firing order ???? It ran fine idle but....!!!

 

Robert

[tlr426]

I found a diagram for the firing order for a marine 454... What is the difference between standard rotation and reverse rotation? How do I determine which is which?

[GAMBLER]

To figure out if it is a fuel issue, get a 6 gallon tank and hook it up to the motor.  Use fresh gas.  If it runs like crap, you can throw the bad fuel issue out the window. 

[Shellback]

Are you sure he installed a marine shortblock?  I followed a motor issue on another website where the fellow didn't have power at higher RPM's. Ran fine at lower RPM's. Turned out to be the camshaft. Auto or truck engine cams are designed to get power at lower RPM's. Whereas boats get power at higher RPM's. Scratch some paint off a freeze plug, if it's a marine engine, they should be brass. If it's steel, it's most likely not a marine engine.

Edited June 18, 2014 by Shellback

[tlr426]

Hopefully its a marine engine they paid more then enough for it... Infact they got hosed for sure just trying to stop the bleeding. I will check that out and see if its not a marine engine I'm sure they have a case against this "mechanic"!

[tlr426]

All fresh gas tank was flushed and its new gas was added at the marina

[slow rollin]

Also it will have merc cast in the block on the left hand side behind the exhaust manifold.

[Xxx]

OK, I will throw my 2 cents in hear, if you have a points system the distributor (timing) should be set up with the motor at 650 rpm. The timing should be set at 8 degrees BTDC. If they set the timing with the motor any faster the mechanical advance is coming into play and then at 2000 rpm where full advance timing occurs it should be @ 26 degrees BTDC. If it wasn't set up this way you will have to much timing advance and this will cause a loss of power at higher rpm, meanwhile everything will seem ok, like at an idle or just putting around. Just food for thought