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Evinrude 150 HP rebuild

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etd66ss

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I am rebuilding a 1984 150 HP crossflow powerhead.

I disassembled & cleaned the block. All the bores measure 3.5012-3.5016.

I was getting 84-85 psi in all the cylinders before disassembly.

After deglazing with a hone, there are still 2 deep scratches left, one of them in cyl#1 that runs the full length of the bore, and another in cyl#4 that runs about halfway down the bore from the top.

How deep is too deep? I can definitely catch my fingernail on these scratches,they are an estimated depth of .004-.006 deep.

Not all the bores cleaned up 100% with the hone, they all seem to have a patch at the bottom of the bore, intake side that will not deglaze, and almost looks like they have water spots on these patches.

I'd hate to have to bore these out, was hoping for a re-ring only, as they are still a good size for STD bore pistons.

Need opinions from powerhead builders.
 
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How do the cylinders measure where the hones did not touch ???---------How do the pistons measure and what is the total clearance when you reassemble the used pistions ??------------More that 0.008" ??-then I would consider rebore all.--------Have you looked at piston ring grooves for wear ??
 
I have not taken the pistions apart yet. I guess I will do that, clean them up and measure.

I'll try to re-measure the the bores in those specific spots.
 
Your piston / clearance measurements mean nothing !!--------You can only determine clearance by measuring piston skirt in ONE spot .-Sorry, but you need to invest in a factory manual.--It will be cheap in the long run.
 
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I have a manual, but it does not even give me the size the piston is supposed to be.

For the bores, I was using a bore gage, and measured 1" down for the "top" measurements, and then about 1/2" from the bottom for the "bottom" measurements. However, it was a 3 legged bore gage, not a 2.

For the pistons, I measured just under the lower ring groove for the "top" measurements, and about 1/4" from the bottom for the "bottom" measurements.

The manual I have only shows a picture of a caliper on a piston checking for out of round before installing, does not go into any detail about where to measure the pistoon, and how to calculate the clearance.

My clearance measurements in my pdf are just comparing each piston top to each bore top, each piston bottom to each bore bottom. If there are specific locations on each part where the two measurements are to be taken for clearance calculation, I can certainly retake all the numbers.

Also, when you said .008", I didn't know if you meant .008" total, or .008" per side. You did say "total", so I assumed .004" per side max allowable clearance.

The service manual I have, I bought form this very website...
 
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No offense Mate with this.

You clean up the bores and yr finger nail picks out a scratch?

Rebore and check your crankshaft/ main bearing tunnel as well.

Next is where the Hell did the scratches come from?

You have some reading to do in yr manual Mate.

Else yr pissing money against a wall for longevity of your engine.

B
 
When I disassembled this powerhead, I could tell it was previously "rebuilt", as gaskets were not used in many places, only blue permatex. I know that is not factory...

The pistons have corresponding gouges in them wherever there is a scratch in the bore, however, the rings are not damaged. As far as I can tell, some kind of cantamination got in between the pistoon and the bore. Maybe the last guy to do the rebuild/re-ring job didn't do it real clean.

I'll reread the powerhead section of the manual again, but, I see no procedure or table showing me the bore to piston clearance. If someone has the 1978 model 150849 service manual, and they know this info is in there, please tell me what pages.
 
To get clearance values pistons are only measured 1/4" from bottom of skirt 90 degerees from connecting rod.------------On worn pistons usually you would use the smallest dimension there.( worn spots )----------------A new piston would have a taper and is usually about 0.010" smaller in diameter at the rings.
 
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Alright, thanks for that info!

But anyways, I'm likely looking at a total rebuild if I'm gonna put this back together, boring + new pistons, etc.

My $200 craigslist winter project just got a lot more pricey...
 
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There is no doubt in my mind that you need to rebore all.----------------------The cylinders are worn.The pistons are worn.Ring grooves are worn.--------------Put a motor together like that and yes it will run.-------------It will be noisy and just will not last.Just look at the angle of the top ring. When piston is worn and ring groove is worn then those rings are too loose.-----At 5500 RPM bad things happen.
 
Yep, agreed...

I just have to decide what I want to do.

So far:

$200 for motor off Craigslist, bought it because it was cheap, and had even compression, and wanted a winter project :)
$225 for used crank off eBay, due to the fact the top bearing in the motor I bought was not getting lubrication, rusted and ruined the top journal. Also #6 journal had erosion on it, meaning I need to replace that bearing ~$30.
$60 for 6 used eBay connecting rods, some of mine don't look perfect. Of the 6 I bought, 3 look good, and I have 3 from mine that look good.
$32 used eBay crankhead bearing & housing, as a new one was over $300...
$85 used eBay starbord head, as the one on mine had a sparkplug hole thread fix that was a disaster. (bought this before I realized I had low compression heads, now I want high compression heads...)
$54 eBay carb rebuild kit
$87 eBay powerhead gasket kit
$45 Amazon.com thermostat kits (2)

$820 boring & 6 new Wiesco piston kits.
$600 all new CDI electronic ignition parts, stator, pickup, coils & new motor harness. (I wanted to upgrade from the 1978 coils & power packs to the newer style, lot of money just to do that...)
~$200 lower unit is going to need some attention.
~$200 paint and other unforseen stuff.

$ 788
$1850


$2638! :eek:


When I bought this motor, I was hoping to put no more than $1000 into it. Such is life...

This isn't my first build. I rebuilt an '81 90HP Johnson about 15 years ago that is on my Dad's boat, still running, so I do have some confidence in my abilities. I was going to replace that 90 with this 150.
 
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