Cracks between intake scallops, '79 150hp Evinrude

[boatnut74]

I have a '79 150hp Evinrude that has a blown piston (top port side) I believe it was due to overheating or carbon build up as it still has the high ring groove pistons. As I was inspecting the block I noticed cracks between the intake scallops. They don't go into the sleeve. I was just wondering if the block is still useable or if I should find a different one.

It is hard to see the cracks in the pic. I tried to highlight them with a white crayon to make them more visable.

 

[jimmbo]

Re: Cracks between intake scallops, '79 150hp Evinrude

The cracks are in the aluminium, there is a cast iron sleeve between it and the piston. I doubt very much the sleeve has cracked so you should be able to reuse the block

 

[boobie]

Re: Cracks between intake scallops, '79 150hp Evinrude

Check the sleeve very closely as I've seen them crack before.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

The cracks are only in the aluminum. I just wasn't sure if heat and vibration would cause any more cracking.

 

[emdsapmgr]

Re: Cracks between intake scallops, '79 150hp Evinrude

A common failure on the high-ring 1979 models. My 79 200 cracked a bridge after a high rpm overheat lockup. If the aluminum bridge between the ports is cracked, the block is junk. That's a high heat/stress area. No need to spend time and $ for to overhaul that block only to have it fail shortly after you did all that work. With that damage, it's not worth re-sleeving either. That 150 block is a common one-you should be able to find a good used one in a marine salvage yard that's suitable for rebuilding.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

Well it looks like I might be better off finding a new block. I pulled the rest of the covers off and find something else I was concerned about. It looks like the aluminum is flaking away.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

I guess my next question would be what years of blocks will work for the rest of my parts?

 

[emdsapmgr]

Re: Cracks between intake scallops, '79 150hp Evinrude

The 76-78 blocks use the older belcrank shifting mechanism. I'd stick with a 79 and newer to match up to your lower unit shift rod. Your original block is a low-port block, used on both the 150 and early 175 engines. If you find a flatback block from a 200, (1979 up through the 1984 185) they will also work. If you happen across a complete powerhead, such as a flatback 175/185/200, you might want to use those carbs instead of your 150 carbs.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

Would this block work or is it to new?

http://www.ebay.com/itm/390371046198?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

 

[emdsapmgr]

Re: Cracks between intake scallops, '79 150hp Evinrude

That block should work. As noted you would need to overbore one cylinder. That's an acceptable factory fix. It has the drilled holes on the exhaust cover for the trim box-would seem to confirm the year they state that it is. Price is OK in my mind-if it is rebuildable. Only problem in my mind is whether the block is a feshwater block. I'd ask the seller that question on ebay. Personally, I would not buy a saltwater block. The seller's location may tell you something about that.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

He said "50/50, it's a good block" I found another one on ebay that is an '84. It says it is freshly bored on one cylinder and honed on the rest. They are asking $175 for that one, so basically the cost of machine work.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

I spoke with one of the local marine repair places and they said they have a complete powerhead off a '76 175hp. They want $250 for it. If it includes carbs and all the electronics I could easily get my money back out of it. I am going to take a look at it tomorrow. The only thing I'm worried about is the shift linkage connection.

 

[emdsapmgr]

Re: Cracks between intake scallops, '79 150hp Evinrude

The thing about the old belcrank lower units is that they shift backwards from the later models.

 

[boatnut74]

Re: Cracks between intake scallops, '79 150hp Evinrude

My shifting mechanism is on the intake manifold. So couldn't i just use my old intake?
I did pick up the other block today. According to marineengine.com it's a 77. The only difference i saw was where the power pack mounts. The 77 block only has one pedastal on each side where my 79 had two. I think I can make it work though.

 

[emdsapmgr]

Re: Cracks between intake scallops, '79 150hp Evinrude

The shifting mechanism is driven off the intake manifold on the later engines. Yes, you can transplant that 79 intake manifold. When you do, that will upset the timing pointer, so you will have to index the pointer with the flywheel when reassembled, then set the timing to original WOT specs. You'll can probably work around the blocks' single power pack mounting. The big thing is that you must insure the packs are properly grounded.