90 HP 3 cylinder 2 stroke - suddenly running very rough, puffing air/fuel from lower carb

[jim_s]

Funny you mention that - I was sort of going through the mental gyrations of trying to consider Loctite at one extreme (Always blue - I never touch the red - I have yet to meet a bolt that I didn't eventually need to pull back out for something! , anti-seize at the other extreme, or just naked metal. (I have to say, I was amazed at the condition of the bolts that came out of the block - all amazingly clean, dry/oil-free, and no corrosion at all!)

I was definitely leaning toward a dab of blue Loctite, so I think you've tipped the scale there.

I'd still like to torque them down to spec, if I can find it, though. (I was also surprised how easily they all came out - with that many bolts, it was almost guaranteed there'd be one or two MF'ers, but they all came out without any trauma or drama.)

 

[jim_s]

For any future shadetrees interested in the intake/reed cover bolt torque, the Seloc manual proclaims it to be 80 ft-lbs. The reed block bolts (ie, that hold the reeds to the reed block) is listed as 90 in-lbs.

 

[jim_s]

Yikes! DONT USE 80 ft-lbs - major derailment between brain and typing fingers! (You'll likely strip something if you use 80 ft-lbs!) Its EIGHTEEN (18) ft-lbs or 24.5 Nm for the intake manifold bolts. (And, FWIW, I couldn't get anywhere near 90 in-lbs on the reed bolts - just not enough to hold onto on the reed blocks, but they recommend locktite, and there are fold-over tabs, so I snugged mine down as far as I could holding the reed block in my hand (one hand on torque wrench, one hand holding reed block - vs putting the reed blocks in a vise, which sounded like all kinds of bad things about to happen), which was about 50 in-lbs, then locitite'd and tabbed - they're not coming undone.

REPEAT - DON'T TORQUE THE INTAKE MANIFOLD BOLTS TO 80 ft-lbs!!

THE CORRECT TORQUE FOR THE INTAKE MANIFOLD BOLTS IS 18 ft-lbs.

 

[Texasmark]

Pulling the gear would only require pulling the pump, reinserting it and reinstalling the pump. As a precautionary measure, running premix until you are sure you are using oil....checking the oil level in the tank.

The oil sensor is a float level sensor in the oil tank and has nothing to do with flow other than oil dropping down low enough that the magnet flips the switch and shorts the wires causing an alarm. A lot can happen from full tank to activated alarm. Your engine, your decision. Flow sensors are expensive for fuels so I would assume one for the oil would be bulky and expensive. On Merc having already done it, a lot probably went into that decision, including look at what others are doing in the field.

Yes by the time the OT goes off it's too late.

 

[jim_s]

I hear you on the oil thing. Its a bit of a quandary for me, as to what to do. Clearly, I've got a number of smart, experienced folks recommending moving to the pre-mix solution. There is obviously concern about gear failure, but Chris from CCMS's stated concern was the low oil ratio present at the time of the hole shot, not gear failure. On the other hand, while I've found a number of horror stories about other Mercury motors (mainly 6-cyl motors, with plastic drive gears) dying due to pump gear failure, I haven't come across any clear cases of that happening with this particular motor. (best I can tell online, this particular motor has a metal drive gear - I guess it'd be easy enough to pull it out and look!)

Anyway, my inclination is to punt on this decision at present, leave it injected, and do some more research/pondering on it in the mean time. Truth of the matter is, the convenience of having the oil tank is very appealing to me, but if it meant saving my motor from disaster, I'd definitely forgo the convenience - I'm just trying to determine how real that possibility is. (This coming from the guy who had a zip tie make its way into the intake and get lodged in his reed valve... <

I spent part of one evening pulling the intake system apart, part of a 2nd evening getting it all cleaned up (getting the gasket material unstuck from the block was a serious PITA, and every surface associated w/ the lower-most cylinder was 10x harder to get the gasket material off than the other 2 cylinders...). It all went back together quickly and easily this 3rd evening. Carbs are synchronized - just the timing left to check tomorrow.

The CCMS reeds look nice - I'm anxious to see how they work out!

 

[Texasmark]

Let us know.

Interesting comment about Hole shot oil ratio with VRO. He has a point, surely. Question is the pump will immediately respond to the spin up of the crankshaft. However it will take time for the oiler to dump the extra oil into the fuel inlet hose over where the control cables enter and then that fuel to get up to the carbs bowls via the fuel pump, and finally get in the venturi and to the cylinders. Guess a good silicon or silicon based oil (Pennzoil Semi Syn from ww is what I used) would help to keep things slick till the increased ratio hits the cylinders. One would surely think that Merc. engineers thought through that process. Yea verily, idling doesn't require much oil, but hammering down in the hole shot is THE stress point of the entire outing.

 

[ondarvr]

At lower RPMs excess fuel (mostly oil) tends to accumulate in the crankcase, so there shouldn't be an issue of too little oil when first accelerating.

 

[Texasmark]

At lower RPMs excess fuel (mostly oil) tends to accumulate in the crankcase, so there shouldn't be an issue of too little oil when first accelerating.

That's true and apparently drove Mercury to build the slant forward power head white colored fishing motors back in the 60's, besides enabling the lower unit to more easily slip over obstructions. I remember when I did a lot of trolling with 50-100 hp range engines I'd run a lot smoother and longer without smoking if I tilted the engine up a few degrees.

 

[jim_s]

Oh, that was another take-away from talking w/ CCMS - he asked what type of oil I used, and when I said Quicksilver Premium Plus, he actually LOL'd. I asked why, and he basically said because I was getting screwed on oil. :-o He recommended moving to the Penzoil synthetic or semi-synthetic blend, and paying less than 1/2 the cost of the Quicksilver stuff. I checked WW here, and they seem to stock Penzoil XLF. Is that a suitable 'synthetic or semi-synthetic' oil? (Looked around online, and there seems to be much confusion about any differences between XLF and Penzoil Premium Plus - people saying that not even Penzoil themselves has explained the actual difference when asked directly...) Certainly, at the WW price of $17.68/gal, the XLF is very appealing!!

Interesting idea on the low-RPM operation sort of stockpiling lube, and it being available at the hole shot.

In syncing/linking my carbs (as per the Seloc manual), when I got to the step for setting the oil mix valve, I set the idle-level setting a little on the high side (a little bit toward the full-throttle position), figuring that would up the oil content a bit at lower RPM and idle speeds. (It doesn't cause the pushrod to the oil valve to bottom out or such at full throttle, so it seems Ok.) We'll see if that leads to any excess smoking or such.

Started up the motor in the driveway this evening, just to be sure all was working before dragging the boat back to the lake tomorrow. Between the new reeds, and adjusting the timing, it was idling better than its ever idled before. Anxious to try it out at other throttle settings in the AM!! (7am ski session is less than 7 hours away - time for bed!

 

[Texasmark]

I used the premium plus semi-synthetic for half the price of Quicksilver. Don't know about the XLF nor do I know what the acronym means unless something like Xtra Low Friction.

 

[jim_s]

Yeah, the XLF vs Premium Plus thing is a bit of a mystery. (XLF seems to stand for eXtended Life Forumla...) The marketing spew on the Penzoil site makes it sound like the XLF might have some extra anti-fouling/carbon additives, but who knows. For the price difference, and easy availability, I think I'm going to try my luck w/ the XLF, though.

The engine ran great again today - the new reeds are doing their job, and no zip ties in the intake yet! There is nothing life-changing about the performance of the reeds - in the end, I'm still working with an aged 90hp motor (I was hoping the reeds would transform my little tub into a tournament ski boat... ;-), but its idling smoother, for sure, seems to have a wee bit more oomph about 2/3 way of getting onto plane (very subjective, I know, but there was definitely a little bit of kick there today, that I've never noticed before). It still doesn't like to be firewalled from a dead idle - it'll cough and hesitate for a moment, if so, but I'm led to believe that that is a characteristic 2-cycle behavior. (Does anyone know if messing with the idle timing would potentially put things in a better state for the hole shot?) Gas-wise, again, its subjective, but our Saturday morning routine is pretty repeatable, and we consumed less gas this morning than we usually do on our Saturday morning ski sessions, so I'll have to try to track that, and see if there is anything more to it than hopeful thinking.

Anyway, the boat is back alive, skiing is again happening, life is good. Thanks for everyone's interest and help on this, its been fun and educational, for sure!!

 

[ondarvr]

Hesitation off idle is not a characteristic of a 2 stroke, that is unless somethings not quite right. It still needs a little fiddling, probably needs to run slightly richer at, or just off idle.

 

[Texasmark]

Hole shot: Open up the low speed jets until it takes the throttle, just a wee bit at a time. Manual says carbs are sensitive and sweet spot is narrow.

Idle rpm is set by the linkage adjustment knurled, spring loaded screw just above the cable attachment point for 675 +/- 50 in the water, boat moving, F gear, throttle set to idle.

Idle timing sets the idle speed, not carb tweaks like a lot of engines were/used to be. The manual specifies idle timing around TDC whereas at WOT it up in the 20-22 BTDC area.

Next, if you are running a lot of pitch and have a heavy boat, get some ports in your prop if you don't already have them. What's happening is that the 2 stroker doesn't have the cubes to come off idle with "engine mass" to help you get started like a big block V8 for example. So you have to lighten the load to compensate.

Either run a low pitch prop which hurts you on top end or run a "simulated" low pitch prop via prop porting. The Laser II SS is an excellent example of a nicely ported prop that gives you the best of both ends of the rpm spectrum.

Go up to the Boat Parts and Accessories section and in it, scroll down to props and in the prop section fiddle around till you find the tutorial on props where rake, cupping, porting, and a few other things are adequately explained.

What I just told you is what I have learned with my 2002 90 triple over the years. Had lots of fun with that engine.

 

[jim_s]

Great info and advice on the low-speed jet adjustment and idle timing, Texasmark and ondarvr - Thanks! I'll definitely work with those parameters a bit, and see if I can dial in a bit better throttle response to the hole-shot.

I'm presently running a 12.8x19 4-bladed prop, which really helps with the pull-up, as well as maintaining a reasonably consistent speed at skiing speeds. I've experimented with a number of props, going as far down as a 17 pitch 4-blade, which was really great on the pull-up, as well as for pulling tubes, but was too limiting on the top-end for slalom skiing. So, the 19 pitch 4-blade seems like the best all-around compromise I've tried so far. (I also run a set of SmartTabs - so, between the 4-blade prop, and the trim tabs, there's really very little to complain about the pull-up - it's just always nicer, the shorter/quicker it is. I have friends with Masercrafts and Nautiques, and you're barely done saying, "Hit it!", before you're up!)

When out tubing, we've generally got a full load of kids, but when skiing there's usually just 2 people, occasionally 3, so I don't think weight is too big of an issue. (That having been said, the pull-up is perceptibly faster and easier when there's just the skier and the driver, than where there's a passenger, as well.) The boat itself weighs in at about 1400 lbs with 3/4 tank of gas, so is fairly lightweight overall. I've got friends with larger/nicer I/O boats, with more powerful engines (mostly 135 hp Merc 3.0's), but I still end up with a better power:weight ratio - it usually feels like an exercise in self-imposed waterboarding, trying to get up on a slalom ski behind some of their nicer boats. I'll take my little tub for skiing any day. (I've also got a home-brew speed controller on the boat, which dramatically improves the skiing experience, but that's another thread altogether.

Yes, I've been very pleased with the 90hp 3-cyl 2 stroke - great engine - I hope it lasts many more years!!

 

[Texasmark]

Great info and advice on the low-speed jet adjustment and idle timing, Texasmark and ondarvr - Thanks! I'll definitely work with those parameters a bit, and see if I can dial in a bit better throttle response to the hole-shot.

I'm presently running a 12.8x19 4-bladed prop, which really helps with the pull-up, as well as maintaining a reasonably consistent speed at skiing speeds. I've experimented with a number of props, going as far down as a 17 pitch 4-blade, which was really great on the pull-up, as well as for pulling tubes, but was too limiting on the top-end for slalom skiing. So, the 19 pitch 4-blade seems like the best all-around compromise I've tried so far. (I also run a set of SmartTabs - so, between the 4-blade prop, and the trim tabs, there's really very little to complain about the pull-up - it's just always nicer, the shorter/quicker it is. I have friends with Masercrafts and Nautiques, and you're barely done saying, "Hit it!", before you're up!)

When out tubing, we've generally got a full load of kids, but when skiing there's usually just 2 people, occasionally 3, so I don't think weight is too big of an issue. (That having been said, the pull-up is perceptibly faster and easier when there's just the skier and the driver, than where there's a passenger, as well.) The boat itself weighs in at about 1400 lbs with 3/4 tank of gas, so is fairly lightweight overall. I've got friends with larger/nicer I/O boats, with more powerful engines (mostly 135 hp Merc 3.0's), but I still end up with a better power:weight ratio - it usually feels like an exercise in self-imposed waterboarding, trying to get up on a slalom ski behind some of their nicer boats. I'll take my little tub for skiing any day. (I've also got a home-brew speed controller on the boat, which dramatically improves the skiing experience, but that's another thread altogether.

Yes, I've been very pleased with the 90hp 3-cyl 2 stroke - great engine - I hope it lasts many more years!!

"I have friends with Masercrafts and Nautiques, and you're barely done saying, "Hit it!", before you're up!)"........APPLES and ORANGES.......probably 185 hp, weight is amid ship, hard chine, very low dead rise at the transom, may have tabs and all.

Enjoy a good engine.

 

[jim_s]

They're more in the 350 hp range. Yes, most definitely comparing an apple to an orange with fire painted on the side, that levitates on command, and that reaches 5% of the speed of sound in about 2 seconds flat! ;-)

I do love my little tub, but I do aspire to a more powerful tub some day. In the mean time, the little tub does us just fine, though! The fun-per-hp ratio can't be beat!!