General Engine Rebuild Questions

[fmjnax]

Thanks guys. I think at this point I have decided to have a professional do a short block rebuild for me. I am already throwing more money at it than it is really worth, so I feel best throwing just a little more for all new parts installed by a pro.

 

[racerone]

It is worth spending money to do this properly.---Rebuilt some of these 10 or more years ago and still running like they should.---Nice and smooth and idle like new.

 

[fmjnax]

As if the first piston wasn't reason enough to warrant my rebuild, during teardown this is what I found on the other side. The cylinder isn't grooved, but it sure looks like something blew up in there! And this wasn't even the cylinder with the low compression!

Oh, and is my head shot? It is pitted all to heck and doesn't look like it would be fixable (and frankly, I may as well just buy a new one for piece of mind).

 

[emdsapmgr]

So, now I see the damaged ring, which I mentioned above in #4. The factory will tell you to replace the head and piston. Their fear is that the damaged surfaces will develop "hot spots" that might cause detonation when running after overhaul. The piston is scrap. I would not use the head, nor would recommend that you do. You may hear some comments on this site where they've lightly sanded and re-used heads. It's your risk. A bad thing would be if there were some ring shards embedded in the head and it came loose while running-after the new overhaul.

 

[fmjnax]

This is the other side of the motor, emd, but yeah I see the ring too now that I look. Basically, both sides of the V4 blew up! I'm not even going to mess with that head. It had overheated long before I became the owner because the temperate plug monitor is fused/welded to the hole in the head and I can't get it out. I'm tossing it and getting a new one for sure. I'm having the block rebuilt with all new parts as well. I'll probably spring for new carbs, too (because I have strong suspicion that the previous owner put the wrong ones on it, or didn't use the correct orifice plugs).

I still don't know what caused it, though (I suspect the carbs). On the left (port) it was the top. On the right (starboard) it was the bottom. I have no idea how it was running at 47mph last season, let alone how it was running at all. I'm just glad I didn't throw a rod, do major block damage, or do any personal damage. I'm kind of excited thinking about what it will run well all 4 cylinders are good.

 

[ondarvr]

I would probably just get rid of this motor and buy something much newer for about the same cost as rebuilding. My 98' 90HP Evinrude did about the same thing, only on just one cylinder, picked up a 2005 Merc 90 for much less than a rebuild and am very pleased with it.

 

[fmjnax]

That was my first initial plan ondarvr, but I weighed my personal pros and cons out, and rebuilding won out. No matter what, I'm out a good chunk of money. What is going to get me my best return on the money?
A - Ditch the boat for cheap/free and eat the loss. No extra costs. No return
B - Rebuild the engine PH. If I have it rebuilt, I KNOW it is good and with brand new parts. No worry of getting burned on a Craigslist or internet buy. I rebuilt the lower unit with all new parts last summer. Having a practically new PH means the entire engine is practically new. Local short block rebuild of around $1200 gives a decent return
C - Repower with a newer used engine. I could get an old one cheap, but that defeats the purpose. Around here, I'm looking at over $2000 for a 90's engine in the 115-150 range. I'll have more costs incurred and there is potential for return, but there is also potential that something major is on its way out or that there is an underlying reason why they are selling the engine.

I just feel best knowing that everything has been rebuilt and is "new". Personal preference, I guess. I know I will never get my money back out of it, but that has never been my intention anyway (I'm fully restoring the hull as well. This is a keeper boat).

 

[wayneo99]

I was in the exact position 2 yrs ago and thought the same thing. I bought a OBR power head thinking im good for the next 10yrs. how wrong I was.

in reality its not if your V4 crossflow is going to break a ring and burn up its WHEN..... its a known problem.
cut your losses and invest in a newer engine.

search this forum for broken rings, low compression etc... and you will see its only a matter of time.
no disrespect to the pros who are on this site and have done many good rebuilds but the history of the V4 crossflow in my opinion is a time bomb.
good luck

 

[racerone]

Wiseco pistons use a different ring design.--Very good alternative !!!!!!!!!!!!!!!

 

[fmjnax]

Well I know next to nothing about that actual pistons and such, but the local marine place I am taking the block to mentioned wiseco when I was talking to them on the phone, so I guess that is a good thing for me! They do their own machining in-house, build it back up, and do a 4 hour break in. They have good reviews locally and they are family-owned so it's worth a good go for me. If V4's really are bad (are they as bad as the FICHT's?), then I will cross that bridge when I get there.

I do appreciate all the advice to jump on to an entirely different engine and I don't want to sound stubborn and irrational, but the original parts went 30 years. If I can get even 5 out of it, that's probably good enough for me. I'll be done with my schooling by then and will be in a position to go ahead and buy a late-model boat and get away from all the old stuff. I'm just biding my time, ya know.

 

[racerone]

There is absolutely nothing wrong with the " cross flow " design.-------The fault is the wild taper on the top piston ring.-----Just draw a picture of the top ring in the groove and then visualize what happens when that ring wears !

 

[ondarvr]

The cross flow motor's are OK, but it's a 50+ year old design and was continued because it was cheap to build. They had problems with the rings and the locating pin for the rings too. Mine had the locating pin back out and gouge the cylinder wall, when it finally broke it took the rings, piston, cylinder and head with it. When I stepped into the future by going to a used 2005 Merc 90 for $2,100.00 (this was a couple years ago), the difference in performance was greater than I thought it would be. I wouldn't even think of buying another cross flow. If you plan to change the carbs and other things the cost will go up, the power pack will probably fail soon too. along with coils and assorted other things.

The Weisco pistons should work better than stock. I never like putting money into old motors, you normally end up chasing issues until you get rid of it.

 

[emdsapmgr]

It's obvious that restrictions in your water flow contributed to the overheat. Possible that a carb problem also contributed. I would not be so quick to ditch your carbs. Since the engine failed, it's always best to do an autopsy on the carbs to see if they may, in part be part of the problem. I'd pull the carbs apart. Even down to removing the two main jets in each carb. Visually inspect them and the carb bowl passages for "debris" or restriction. For instance: improper (or lack of) winterizing and bad fuel can cause today's fuel to become gel and even crust over when stored over a winter. (This is not a V4 crossflow problem-it's an owner problem.) Dried fuel can create a restriction, causing a lean fuel condition, which absolutely lead to the failure you have. Best to have a close look at this-your carbs may just need a good cleaning with a special carb cleaner, such as a Gumout type product. They will probably work just fine with a good cleaning. You'd want to do this anyway, prior to reassembly on the rebuilt powerhead.

 

[fmjnax]

*Note* Since this is no longer about just the low compression on a cylinder, I've changed the topic title.

No doubt flow was a major factor. During teardown, I found that the thermostats and relief valves were bad/stuck (not sure what that impact was exactly, but it couldn't have been good). I couldn't tell for sure where it came from, but there was A LOT of oil; down the exhaust, underside of the block, down the midsection, and all over the "pan". At least one gasket somewhere had to have been blown.

As for the carbs, I had cleaned and rebuilt them and soaked them in Berrymans before I ever cranked it up (and then a few more times after that as I was chasing down an idle issue... which I now believe to be caused by the low compression). Yes, they were gummed and varnished. The orifice plugs were severely restricted or plugged. The boat had been sitting for a while when I bought it so I don't know if the previous owner was running it with the carbs like that or if they ended up gummed just from the sitting. No way of knowing for sure.

I stripped them down last night and noticed something I hadn't noticed before. The orifice plug for the top left cylinder (the one that had the low compression) was sitting higher than the other 3. I pulled it out and found that at some point in the past, someone broke a plug and either pulled it out or drilled it out. There is some brass threaded in there, thus why that plug sits a touch higher than the other 3. The passage isn't restricted and the plug seats down fine; albeit a thread high, so I don't know that this is a problem now. Music wire runs through it fine and I can spray carb cleaner or air through it fine. I wonder if the previous owner (whom was a certified ASE mechanic) noticed the low compression, traced it down to that orifice plug, tried to remove it for replacement, broke it, drilled out what he could, and stuck a new on it and called it good. Certainly seems reasonable, huh?

So any opinions on the above issue on that carb?

And on a new note, is there really any reason why I could not rebuild the powerhead myself? It is currently stripped of EVERYTHING possible and just need to be lifted off the rest of the engine. From what I see/read, I think I've got all of the hard stuff out of the way. Any special tools needed to do the rest, aside from the block machining and ring pliers? I guess the biggest question I have is knowing what to have the machine shop bore the cylinders to. If I overbore the scored one, do I have them match the other 3, or just hone them?


*EDIT* - I don't have an actual service manual, but I do have an e-copy of one. Poor pictures, but can ready text just fine. It looks like it details out the steps perfectly fine. I should probably read it a bit before asking stupid questions.

 

[wayneo99]

AGAIN FYI
I used a new power head from OBR, larger jets which is what they wanted, retarded the timing which is what they wanted. when is blew up we inspected everything. carbs jets were all clean, fuel pump gaskets were all good. new water pump kit T stats were new that april and looked good,head gaskets were fine and water diverters were not swollen and in the correct spot. it did not over heat in the traditional way. the fuel was always fresh. We couldnt find anything that would have lead to the failure.
I was tedious about making sure it wouldnt happen and it did!

best of luck to you I hope you get a long life out of that crossflow.


Im done with them forever and will be looking to buy a new engine in april.

 

[racerone]

New does not mean better !-----I would rather run with a rebuilt crossflow from the 80's than a new fangled computer / made with plastic motor.

 

[wayneo99]

Racerone
I agree with your statement but It did not workout that way for me. I have way to much invested in a now blown powerhead which is sitting along side the original one that did the same thing 2 yrs ago which was previously rebuilt and a resealed trim unit and lower unit.
I cant put anymore money into it with the crossflows history and my poor results
hind sight is always 20/20
best of luck

 

[racerone]

I have numerous V-4 crossflows for parts / rebuild.---I do know the history of these motors.----Most of these motors are destroyed by lack of care and maintenance.-----I rebuild them and have complete faith in the work I do.

 

[fmjnax]

Next on the agenda is actually getting the powerhead off of the rest of the engine. Everything is stripped down completely. I removed the 4 mount bolts from up top on the "pan". Then 6 long bolts from the mid area (3 on each side). Then I removed 2 nuts from under the exhaust area. Then I removed a bolt and a nut from each side up near the front, kind of by the steering arm area. I don't see anything else holding it on, but it won't budge. I dropped the lower unit to make sure the shaft wasn't seized. Still no movement.

I don't see anything in my e-manual for actually taking the block off, so I'm at a loss. Am I missing something? Any tricks I can employ?

 

[racerone]

Put a nut back on under the exhaust area,----Use a hefty prybar and pry up on the nut.