straight 6 power head part #

[muck chucker]

My 1976 115hp straight 6 melted a piston on the weekend so I went to the local dealer and he had a brand new powerhead there still in the box. Its definitely a straight 6 but when we put the part # in the computer it would come up blank. The part # is 56125a72 and my question is what size inline 6 is it a 90, 100, 115, or 150. My motor has a distributor and so did the new one so I figure it must be close to the same year as mine.

 

[Chris1956]

Re: straight 6 power head part #

I was not able to find it using google. There should be a list tracing it back to the HP and year. You might look at 1976/77 1150, followed by 1500 followed by 90s and maybe you get lucky and find it. Crowley marine parts catalog lists it.

Why not just fix your one cylinder? It is a lot cheaper to replace one piston and bore one cylinder oversize, than buy a new block. You must fix issue that caused problem. Waterpump or carb is likely cause.

 

[mr 88]

Re: straight 6 power head part #

I have seen the oil feed line that goes up the side of the block sliced under the flywheel.That will cause at least #1 to grenade.Is the cylinder wall scored ? Sometimes they just get loaded up with aluminum and can be acid washed clean.

 

[Faztbullet]

Re: straight 6 power head part #

The part # is 56125a72 and my question is what size inline 6 is it

My book shows it as a 135hp,to be sure look to see if it has the small transfer port covers,exhaust plate and carb mounting straight across vs offset.

 

[emckelvy]

Re: straight 6 power head part #

A 1350 is a 99-c.i. block and has similar-style transfer port covers as the '76-115hp. Same carb mounting as well. Where it really differs is the exhaust plate configuration, it's the old-style open-plenum vs the later rectangular-port style with a thick, split tuner plate.

Chuck, take a look at the bottom cylinder's exhaust ports to see if they're extremely large, if so it's likely to be a 150; if extremely small, maybe a 90. The bottom of the powerhead definitely has to match up to the '76 tuner plate or she ain't gonna work.

If it's indeed a 1350 it wouldn't work without swapping-out the entire center section (exhaust tower) as well.

All the 1150 carbs, ign, etc would bolt right up, though. The main jets would have to be changed, as the 115's jets are too small. Hard to find .0785" jets, but .080" would probably work OK.

The 1350 is definitely a Beast and likes to run hard; a brandy-new factory powerhead would be quite a find. Thirsty devil, though, all that power takes more fuel!

Last thought, if you were to remove one of the transfer port covers, you could confirm whether or not there are power-port pistons, if so it would confirm it to be a 1500.

It'll be interesting to find out what it really is!

HTH.........ed