1990 115 Merc Carb amp Jack Plate Question

"Hi, Graham! I've got a co

"Hi, Graham! I've got a couple of questions about a 1990, 115 Merc }I just bought. (1) Engine was laid up almost a year. Wouldn't idle but top end speed seemed ok. I brought it home and ran it on a hose I found squeezing the bulb increased low AND high end. No apparent damage i.e. tight, overtemp, etc... If a carb or carbs are faulty, is there any possiblity of having damaged it? Is the oil injection system still lubricating the engine if it's starved for fuel? At what point is the oil injected? (2) I replaced impeller but it takes 3 or 4 minutes for water to pee out of the tattle-tale. Comes out of prop and foot ok then pees. Water temp is fine. How long should it take to pee? (3) Does this motor run only on the top 2 cylinders at idle? (4) How should jacking plate be adjusted for maximum performance? I know this is a mouthful but I've got a manuel on order but haven't received it yet. Again, thanks VERY much for all that your team does for so many! David"

"Hello David, I don't mind

"Hello David, I don't mind giving you my 2 cents, but there are others on the Merc board as well who have significant experience with these motors.

Anyhow, being laid up for a year if prepped properly is not an issue at all.

Yes, if the oil injection is working, it injects oil (after) the carbs (just before the reeds at the plenum or intake or whatever you want to call it), so even if they were running very lean you would still get a decent oil charge to the cylinders.

This model has it's cooling controll all in one place - under a cover at the top of the top cylinder you have both the thermotat and the poppet valve just separated by a small channel. So the thermostat stops any water flow along that channel until it has warmed up enough to operate - so yes, give it a minute to pee.

Yes, this is a 2x2 design. The top two fire at lower rpms and then the ignition kicks in when you cross over to high speed operations.

Guy who own them note a "less than smooth transition"

The cylinders are still receiving a gas/oil charge all the time - it's the ignition which turns on and the 3/4 cylinders start to fire. Of course all of the carbs are jetted differently to allow for this somewhat odd design.

Jack plate are a whole discussion in themself. Yes the do improve performance - but on a long term scale.

I run a 6" setback, adjustable on my 140 horse. Not because it instantly gave me 5 more mph (which it didn't - got maybe 1 mph - or maybe just picked a bit of tail wind) but because after much piddling around under (my own) test conditions I was able to consistantly save .2 gallons per hour (yes "point" 2).

A day on the water can see me burn 40 gallons of gas, so on a given day I can now save maybe 1 gallon - but I boat alot, so after 2 years, I have paid for the jackplate in "saved" fuel and then continue to save a little bit (but here in Canada gas is currently selling for a touch over 4 bucks a gallon).

So when you put "performance" "jackplate" and "production boat" all in the same sentence, you are talking about a very much "less dramatic" performance increase than comes to mind with most of us.

In almost every case, a jackplate WILL improve performance, just not in a way that you notice "instantly"."