85 hp v4 piston slop ?

[phillnjack]

hello again took head of to replace leaking gasket and was amazed at the amount of slop in the pistons. ive never got to involved with marine 2 stokes till now and wonder what is reasonable slop in pistons. if this was a car engine i would say its *****d but someone said that these engines (1979 johnson 85hp v4 ) get tighter as they warm up. is it usual to have a lot of slop in these engines or is he wrong. i noticed that no 4 piston has 0.30 scibed on it but didnt see it on no 2 piston .also now got to get 2 broken head bolts out of block .would an engine of this age be worth a set of pistons etc or is this engine gonna be too old and worthless. it seems that every time i undo 3 bolts the next one snaps. could the slop be sticky rings and without complete strip down whats best way to clear ring grooves. would decarb spray do the job. ill be waiting for advice on this engine as im thinking its a dead loss

 

[Dhadley]

Re: 85 hp v4 piston slop ?

There is no tolerence for "slop" but there is a wear tolerance. Its possible to measure the cylinder even with the piston still in to get an idea of how much its worn. <br /><br />I think youre on the right path with doing a decarb job. It must have been running OK as you never mentioned a performance problem. I'd suggest you complete the head gasket job and decarb. Like I mentioned, you can measure the top of the cylinder to get an idea as to wear.<br /><br />Dont forget to repalce the deflectors while you have the head off.

 

[phillnjack]

Re: 85 hp v4 piston slop ?

what are deflectors ?. might sound a bit silly but i aint got a clue what they are or where they are.please advise dhadley this is first time on a 2 stroke outboard.

 

[ledgefinder]

Re: 85 hp v4 piston slop ?

Even factory-fresh, they'll feel real loose if you're used to other motors. As DH say, you could measure the cylinder to be sure. <br /><br />Heat helps a lot when disassembling motors that've seen saltwater use. I use a small oxy-MAP torch set if the fastener feels like its going to break. The block is aluminum and the fastener is steel. These expand at different rates, with temperature change, so heat tends to help loosen things up. Was there a 'stub' of the old bolt sticking up, once you got the head off? Generally, heat & PBBlaster on the stub for a bit, then see if a good-quality vice grip will work on the stub. If you can get it to twist back and forth just tiny bit at first, then you're all set. Just keep working it back & forth, using heat & PBBlaster periodically. Don't push so hard that you move the vicegrip on the stub.

 

[Dhadley]

Re: 85 hp v4 piston slop ?

The deflectors are in the water passage in the block. With the heads removed youll see 4 little rubber pieces of hose. 2 on each side. As they get old they will swell and get out of place. Instead of deflecting the water they may actually block the flow.

 

[phillnjack]

Re: 85 hp v4 piston slop ?

i did not mention performance as ive only just got this engine. but on running with muffs on saw water leak from bottom of left head. it runs but seems to pop a bit and does not run as smoothe as i would have thought, its not too bad to start and revs real quick. it sounds very loud compared to mercury 60hp and mariner 80hp.my friends got yamaha 85 and this sounds a lot louder, but wont know what it runs or performs like till get boat on water and give a real try.to me it sounds like i have a engine knock but my friends tell me im imagining it. i always think on the down side so if alls ok its a big bonus. i did not think of doing compression test first (stupid me i know ) but will do after its all back together.so ill order parts and try to get these bolts out.also im not so sure about the block being alloy ledgefinder this one is iron im sure. head is alloy and looks in good condition with no scores. so now to drop the lower cowl and see how many more bolts i break.

 

[Dhadley]

Re: 85 hp v4 piston slop ?

If your block is iron, it'd be the first OMC outboard I ever heard of like that. I'd sure hang on to it rather than running it. Gotta be really rare.

 

[rayjay]

Re: 85 hp v4 piston slop ?

Pistons always are loose at the top. The piston is tapered, smaller at the top and larger at the bottom. When running the piston crown is much hotter than the skirt and therefore expands more. On a 2stroke this is more pronounced due to firing every revolution as opposed to a 4s firing every other rev.