Started tearing down 30hp

Harker

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or 35hp depending on what numbers I believe. AML35D millitary motor. Took the head off and the water passages have redish stuff..probably salt too as there is some white-ish crud in there. What do you use to clean the water passages? The cylinders had some dark spots that look like smudges and I can't feel any scoring with my fingernail. I decarbed it before taking it apart and there is black stuff on the pistons but not much on the head..one side of the head has more than the other around the sparkplug hole. This motor ran cold and rich and I am going to try and "demilitarize" it. I removed a "dewatering" valve and will put all the recirculation hoses back where the stock manual says they should be. What should I be on the lookout for when inspecting the parts? I want to put new pistons,rings and bearings in it,should I have it bored oversize? What is a good tool to measure the inside diameter of the cylinders? Don't know if it has ever been bored before.
 

R.Johnson

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Re: Started tearing down 30hp

My book show's the AM35D to be a 35 H.P. built in 1995-96. You may well not have to rebuild this engine.I am not familiar with what the difference's are on a military engine. If the cylinder walls, and pistons look good, you could well be looking at just cosmetic work. As to how to measure a cylinder bore, You will need a telescoping guage, along with a 2-3" micrometer. You could also measure with a dial bore guage.
 

rodbolt

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Re: Started tearing down 30hp

hello<br /> most the military engines had 1/2 inch wide slots milled from the wrist pin boss to the piston skirt. it severly limited engine life. inspect the pistons. if the do not have the slots and a micrometer shows they are in spec they should be ok for reuse. if the have the slots get another set.<br /> use a dial bore gauge for the inspection. I use telescopeing gauges and micrometers for a rough inspection but I have used them to hold plus or minus .001" for years.<br /> good luck and keep posting
 

Harker

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Re: Started tearing down 30hp

R.Johnson, I have 4 manuals for it...Clymer, Seloc, Johnson factory 1995 and Johnson factory 1990. Originally it was advertised as a 92 30hp. Looking at the pictures in the 90 johnson manual, the parts look more like what is on mine.Rodbolt, I remembered you telling me about the pistons when I first got it..that's why I am taking it all apart. The exaust housing has two holes above the lower motor mount that exaust comes out of and gasses me out while running. I rebuilt the carb, plugged the holes and it ran pretty good for a while..then quit while at wot. I removed the plugs and it ran good again. The link and sync couldn't be done correctly on it, the marks on the cam, when set to run good were way to the left of the knob thing BEFORE giving throttle..when I tried to link and sync by the book, it would hardly start. This motor didn't cost much and has provided a huge learning experience and will continue to do so..I'm having fun with it.
 

G DANE

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Re: Started tearing down 30hp

Harker <br /><br />The two marks should be to the left of the roller. The first "throttle" is given by advancing ignition only. The reason the marks are on the cam is that the throttle butterfly must not open at all before the roller is in center of the two marks. Next to check is then that the linck arm opens throttle butterfly to horizontal when the ignition armature plate is against the rubber stop. See to that the throttle is not opened past horizontal.
 

Harker

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Re: Started tearing down 30hp

Got it mostly apart last night. I have to take the ignition off the top and I'll be ready to split the crank case. What can I use for the "taper" pin tool? Is there something I could soak the parts in to soften the gasket gook and clean the grease and carbon off the parts..or do I just scrape and brush? The cylinders do have some light scoring that I can barely feel with my fingernail. I'm watching ebay for an inside micrometer and torque wrench.
 

rodbolt

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Re: Started tearing down 30hp

hello<br /> if you can feel marks its time to bore it. <br /> make sure the machine shop is intamantly familiar with boring two stroke marine powerheads. I use ron's marine in portsmouth VA. he has done them over 40 years.<br /> the taper pin can be knocked out with a tapered punch. the rod cap bolts will require a 12pt 5/16ths socket. use OMC gasket remover or equvalent and a scraper. we dont recommend wire brushing. the steel imbeds itself in the aluminium and causes problems. I use the 3m pad on a drill. works great and does not eat the castings. other than that its straight fwd. replace the botom main bearing at a minimum and the others as inspection dictates.<br /> good luck and keep posting
 

Harker

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Re: Started tearing down 30hp

Will do Rodbolt. I know of no one in my area that will do the boring and was thinking of sending it out. If I send it to Rons marine, could they just bore it and tell me which oversize piston to buy? I figured on replacing all the bearings while it is apart..don't want to do it again from saving a buck.
 

Harker

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Re: Started tearing down 30hp

If I measure the piston, will that tell me whether the cylinder has been bored before? What should I expect to pay for having the cylinders bored? Thanks.
 

rodbolt

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Re: Started tearing down 30hp

call Rons Marine at 757-397-3451. Ron has a ton of experience dealing with military motors. he does the p-250 pump motors and the seal team motors. that is where I worked when I learned about them.<br /> you can UPS the block to him. send the cyl head for surfacing to. he can assemble the short block if you wish. he normally has all the pistons and bearings in stock. good luck and keep posting.<br /> PS tell him a nut from kitty hawk says HI
 

Harker

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Re: Started tearing down 30hp

Got the whole motor torn down..pistons have a small flat milled under the pin hole.Washed it all down with dish soap and very hot water in the wifes laundry tub. Got some gasket remover stuff for the stubborn bits that wouldn't scrape off. The recirc fitting with screen came out..are these available for sale? Or should I just try to put the little screen and check valve back in? All the bearings and the surfaces they rode on look good,but I'm going to put new bearings in it. There are numbers cast into the top of the block..could these tell me anything?
 

Harker

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Re: Started tearing down 30hp

Oh yeah...the bypass cover has an elbow coming out of it with a short piece of hose,plugged with a screw..any ideas what this is for?
 

G DANE

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Re: Started tearing down 30hp

That hose should be connected to an elbow at the intake manifold, using up the oil leftover in front of reeds. Without this connection it will not run good. No purpose of replacing bearings if rollers and races looks good, just extra $.
 

Harker

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Re: Started tearing down 30hp

G Dane, none of the 4 manuals or parts catalog show a bypass cover with an elbow and hose. I may just re-use the bearings after looking at the cost of them.
 

G DANE

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Re: Started tearing down 30hp

I havnt seen other than clymer. Mine shows the hose on page 261, but only if you know it should eb there. I presumed this is the twin 35 HP, not the tripple small looper ? and they have 2 hoses. One going from intake, just on left side of carb, looking from carb end, to this elbow on upper bypass cover, and one going from upper to lower main bearing. If someone removed the first one and blocked it off, it will be flooded with oil in intake. You mentioned the two holes on midsection earlier. If you mean the two holes on upper part of midsection, about 4" below cowling, they are the iddle exhaust reliefs and must be open, or you will have poor iddle in water. I'v done a couple of these and I have an 84' in my shop right now waiting for winther to get time to finish it ( I didnt take powerhead apart ) so feel freeto ask mee if any queations. I do not have a URL, but if I get your E-mail I can send you a photo.
 

Harker

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Re: Started tearing down 30hp

Yes it's a twin. My books show the recirc hose from the intake manifold going to a T that hooks up to the primer and carb. The two holes were just above the lower motor mount swivel on the boat side of the motor. Thanks for the help..I appreciate all of you guys efforts.
 

G DANE

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Re: Started tearing down 30hp

Thats not the recirc, its a primer hose, it will enter the manifold just above the carb.
 

Harker

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Re: Started tearing down 30hp

Rodbolt, talked to Ron a bit ago...He sounded like a nice guy and chuckled when I told him a "Nut from Kittyhawk" sent me.Got another iron in the fire for this engine..gotta see how it works out.
 

yachtsman44

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Re: Started tearing down 30hp

You guys are geniuses.
I came upon your thread since I am in process of acquiring a 35hp MARS engine and am going to need your kind of knowledge to get it working.
I hope I can count on your guidance.

FIrst thing I am looking for is a spec on the weight of the beast. I can't find anything on the internet like specs, since this appears to be a military version of an OMC engine.

All help will be greatly appreciated.

Any of the troops on this thread around Ft Lauderdale?
 

Harker

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Re: Started tearing down 30hp

Nope, I'm from Michigan. I ended up with a brand new bare block off ebay instead of sending it out for re-boring. Mine weighs about 125-130lbs. I have a cherry 88 20hp off my moms totalled pontoon that I took the prop lower unit off of and replaced the pumpjet lower with. It runs great and am just now breaking it in. I don't know if I would buy another one of those unless it was a hell of a buy...a real pita to figure out. I removed the water drain valve too since I never plan to submerge.
 
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