Rebuild powerhead or buy factory-rebuilt one?

[GlasV162]

I have a 1990 Evinrude 90 hp that needs rebuilding; one cylinder has a bad ring (1/4 of it is gone), and the cylinder is scored pretty bad--although the motor runs fine. I'm babying it through the rest of the season. Is it better to have my boat mechanic rebuild the powerhead I have, or should I buy one of the factory rebuilt ones like they sell here? What are the differences, if any? The cost is about the same either way. Thanks.

 

[Dhadley]

Re: Rebuild powerhead or buy factory-rebuilt one?

Let us guess -- the starboard side broke a ring, right?

Generally speaking if the block is borable and the crank & rods are OK (we'd bet they are) then it's more cost effective to rebuild yours. If time is an issue then just order one here. Have your dealer give you totals on the job both ways.

The big thing is to find the cause and fix that. Don't just fix the damage or result, find and fix the cause. If the deflector part of the dome is OK it's reasonable to think the motor was being lugged. That'll coke up the rings and eventually break one. It usually happens on the starboard side first.

 

[Thumpbass]

Re: Rebuild powerhead or buy factory-rebuilt one?

Let us guess -- the starboard side broke a ring, right?

Generally speaking if the block is borable and the crank & rods are OK (we'd bet they are) then it's more cost effective to rebuild yours. If time is an issue then just order one here. Have your dealer give you totals on the job both ways.

The big thing is to find the cause and fix that. Don't just fix the damage or result, find and fix the cause. If the deflector part of the dome is OK it's reasonable to think the motor was being lugged. That'll coke up the rings and eventually break one. It usually happens on the starboard side first.

what does "being lugged" mean? and why the starboard first?

 

[andy6374]

Re: Rebuild powerhead or buy factory-rebuilt one?

lugging occurs when your engine is not reaching it recommend WOT RPM range, it's working too hard. THis is either cause be setup or being overpropped. A good target number at WOT is 5800-6000 RPMs, what were yours?

 

[Thumpbass]

Re: Rebuild powerhead or buy factory-rebuilt one?

lugging occurs when your engine is not reaching it recommend WOT RPM range, it's working too hard. THis is either cause be setup or being overpropped. A good target number at WOT is 5800-6000 RPMs, what were yours?

I am usually at 5000 at WOT...my manual says WOT should be between 4500-5500 RPM's....so I guess I'm not lugging, correct?

 

[KYHunter2]

Re: Rebuild powerhead or buy factory-rebuilt one?

You'd better be very carefull, babying it.

If that piston seizes , you can do ALOT of serious/ expensive damage, on top of the damage there now.

ie: broken crankshaft, con-rod, damaged block, etc.

Look at the price for a crankshaft, block etc.

Then decide , if its worth it to run the motor.

KYHunter

 

[Theoutdoorsman]

Re: Rebuild powerhead or buy factory-rebuilt one?

Let me save you time looking around..........Mar-Fab quoted me a price of $450-500 for a crank to be shipped from the west coast to them, and this was about a month ago. You do need to stop running the motor to avoid possibly damaging your crank itself, or the journals!!! Too, it's hard to find a GOOD used crank without pitting in the journals. Nearly impossible, I might add. Yours is likely salvagable if you stop now. As noted before, time is your only enemy in rebuilding this yourself. Your wallet will thank you later though, and the knowledge you'll gain will be invaluable the next time you hit the water. Just some food for thought. Good luck in your decission..................ALAN

 

[Cricket Too]

Re: Rebuild powerhead or buy factory-rebuilt one?

GlasV.....5000 WOT RPM is lugging it pretty bad. The minimum you should be at is 5500 and higher is better, think of driving a car at 10mph in 4th gear, your engine wouldn't like it.

I agree with the rest stop using it now. You have a broken ring and cylinder damage, you say a 1/4 of the ring is gone, but it may be knocking around in there somewhere, it will only get worse, making the repair worse.

 

[GlasV162]

Re: Rebuild powerhead or buy factory-rebuilt one?

Ok........a couple questions here:
1: What is the deflector part of the dome, and how do I know if it is damaged or not?
2: I rarely run my motor at WOT for the simple reason: my boat reaches planing speed very easily and a comfortable cruising speed is 3000-3500 rpms. At this range, the boat is on plane without that large rooster-tail for a wake. Is this damaging my motor? When I do run at WOT, it turns approx. 5200-5400 rpms.

My mechanic told me that most likely, the part of the ring that is gone probably shot out through the exhaust port, and advised me to "baby it" until having the motor rebuilt. Faulty head and exhaust cover gaskets were causing water to enter the cylinders, which he said caused excessive heat/wear that caused the ring to break off. However, after reading your comments, I'm wondering if I did the damage by not running at high enough rpms. The gaskets have been replaced,and the motor runs and sounds great--no one would ever know there was a problem with it. However, I have not pulled any skiers with it and have not run it at WOT--the highest I've run it is enough for my boat to plane, which as I said before is 3000-3500 rpms. My prop is a 17 inch pitch. Thanks for your input.

 

[Theoutdoorsman]

Re: Rebuild powerhead or buy factory-rebuilt one?

GlasV162........... Just turning the motor over via key, is asking for trouble. Your mechanic telling you to baby this motor, SHOULD be telling you to STOP turning it over..........period. He may be right in that the part of the broken ring was ejected through the exhaust ports, but unless he KNOWS this for SURE, which I can't see how he would know without cracking it open, I'd stop turning that key ............the day BEFORE yesterday! But then again, it's your money he and yourself are playing with, not mine........ ;-) ........... You might get lucky with just honing 3 holes and boring only the one jug .010 which means, at $90 per piston kit X 1 hole and a gasket set vs. continuing running the motor and spending $90 per piston kit X 4 holes bored ($200) + cost of a replacement crank shaft due scarring a journal (untelling how much the cost), 4 new rods ($80 a hit) one or two heads (depending on the upcoming damage due to neglegence), and a gastket set ($125, God willing you don't throw a rod through the side of the block). Etc, etc, etc.........Get the picture here? Do yourself a favor and stop turning the engine......... I ran mine just like you. I just finished rebuilding mine myself. Now, $1600 later, I'm sitting at my computer trying to help others to NOT make the same mistake I did. Oh yeah..........before I go.........find another mechanic. I'm sure others will agree. Telling someone to "baby" a motor with KNOWN internal damage is........well........just not right. And when you get it rebuilt, consider dropping to a 15 pitch prop to get your WOT rpm's up. And yes, Pampering the motor is killing it. Your motor will leave a lot less carbon buildup by burning fuel more efficiently at higher rpm's. I'd do as others here suggest, and make the use of SeaFoam (available at NAPA auto parts stores) a part of my everyday preventative maintnance. Best of luck to you!.................ALAN

 

[GlasV162]

Re: Rebuild powerhead or buy factory-rebuilt one?

Wow...........I guess I really have done more harm than good by running at lower rpm's. Is it possible that my tach might not be accurate? As for finding another mechanic, I have been through the wringer with them. I just finished filing a BBB complaint against a local dealer here after they SCREWED me on a VRO pump. I finally found one I can trust, but after reading your last comment, now I'm not so sure. It seems that owning an outboard repair business in Maine is a license to steal and abuse the consumer. I've owned this 90 hp for 5 seasons and have always used the 17 inch pitch prop since it always performed great cruising and skiing. About twice a season I would use OMC engine tuner, but I guess that wasn't enough. Thanks for your help.

 

[suzukidave]

Re: Rebuild powerhead or buy factory-rebuilt one?

ok, simple question that confuses me arising out of this and other threads. Assume you have a boat/motor propped correctly to max out WOT at or near the top of its recommended WOT range. how much of the time should you actually run the engine at or near WOT to keep it happy? I am talking about a 120 looper here but it could be for any 2 stroke I guess.

 

[Cricket Too]

Re: Rebuild powerhead or buy factory-rebuilt one?

You don't need to always run at WOT to keep an engine happy, you just have to have it geared (propped) correctly. There is no transmission on an outboard, you get one gear and it's your prop, if you run the right prop so that you can reach 5800 at WOT, then your engine will not be lugged at any other RPM either. You can run 3500 for the next 10 years, and never go any higher as long as you are propped correctly to reach the right WOT.

If you cannot reach at least 5500+ RPM at WOT then your lugging, so that means your lugging it at any RPM. Even if you run 3500 all the time, you will be working that engine harder at 3500 then if you are propped correctly.

GlasV.....OMC Engine tuner is a very good product, it takes a little longer in the engine to do it's job now that they changed the formula, but if you leave it in over night it will do it's job. Seafoam is quicker. You may have just had to much coke built up for any decarb product to take care of.

You say you were running 5400 Max WOT, that's not too bad, but really anything under 5800 is lugging, so if it is actually lower towards the 5200 or 5000 range that you mentioned before, then that's hard on it, especially pulling skiers.

Fall is almost here, chalk it up as the end of the season and take it to a machine shop for a rebuild, that way it will be as cheap as possible and you will all set in the spring....with a 15" prop also.

Also, as far as the mechanic goes, maybe he is relatively honest, but I would be a little suspicious about telling you to baby it. He may just be looking for more money when you trash other parts. Or he could just be wrong and actually think you will be alright, and you might, but why risk it and the money?