2.0 questions?

[vmax80096]

I recently just did a simple rebuild on my 79 175 v6. I see that to improve performance some guys are saying you can run 27cc heads with premium fuel, what can a guy shave off to run say 89 guaranteed fuel. I have stock heads and boyseen reeds. It seems to load up when idling around and I was thinking about purchasing bob's exhaust housing or going to larger air jets. Has anyone tried doing either of these and with what results. I also set the timing as per factory, 14atdc idle, and 18 btdc as in the manual. Lastly, had anyone tried jetting down a size on the mains jets. I know that it seems rich when compared to the plug read on a 2 stroke snowmobile....they like to be a tan brown and my boat plugs are a wet black.

[ssmith007]

Use caution leaning an outboard. T-REX is a 2.0 Litre GURU as well as others. They can probably help you. Good Luck. Smitty

[donmac]

are you reading the plugs on a high speed shut down or after you have idled the motor.

[vmax80096]

Reading the plugs after a pull on the dyno....ran 2700lbs.....and old style marine dyno...not a new one from land and sea.

[ssmith007]

Someone give T-REX a call and see if he will weigh in on this. Thanks. Smitty

[rils]

They load up bad idling around trim up a bit it helps. If the plugs are black after running wot run then drop a size on the main if u think u need too but use caution. Before u do this how many rpms are u turing at wot?Is it fouling plugs or just loading up at idle? Does it run good? What exactly is the problem? If u are just looking for a performance gain swap the tuner for a 200 2.4 bump the compression to 145 and run 93. Leaning it will make it run better but if u go to lean it wont run long.

[T-REX]

Fergit tha exhaust snout, nutt'in but sum noise and a place fer ya mid to start crack'in...Pluss it will take sum much need'd bottom end grunt....Kick ya time'in up to zero-10+Btdc(1200rpm on tha hose, 900 in tha water)...U will have to close the butterflies all the way, then use the time'in to achieve tha idle rpm U want)...Top end time'in will do good @ 24* wit out the time'in box....Mix ya oil @ 40-1, and if ya plugs are still black and wet after the time'in jump, either take off ya airbox, or drop .002 on mains....Heds should be cut for your intended use...If ya wanna run regular gass, leeve them alone, if premium iz in ya future, 29cc's will help ya grunt, but keeps ya safe incase ya git a bad slug ov gas(never know what ya buy'n around here)...Drill the 10, 1/2" holes in ya mid(like the performance mota's) and go to a 2.4 200 tuner, and it won't git much better for all round performance(the holes are underwater at idle and gitt'in out tha hole, which gives backpressure for good bottom end)...

I quess tha whole thang revolves around what exzakly yo plans are for ya rig...ski'n, all out runn'in, or allround river bote....Ya kan't have ya kake and eat it too!!!.....Good luck

[vmax80096]

Thanks for all the replys!. I use it for skiiing and run it on a 17.5ft j-craft which with motor probably weighs in at 2000lbs, using a 21 pitch stainless. T-Rex questions? I have the timing set at 14atdc and 20btdc like the book says now you say to go to 10 btdc at 1200 on the hose at idle and finish at 24 btdc wide open. I have a 78 200 bottom end, will that have the tuner in it that I want? What exactly will it do for me? I'm really looking for more bottom end and would like to stay with the regular 87 octane fuel....very expensive up here in cananda and believe it or not can't always get 91 fuel at all gas stations. If it still loads up idling around to lean out the idle do you increase the idle jet size or go down, are they for fuel or for air? I'll check back later tonight for replys....again thanks to everyone for their input!

[T-REX]

I have the timing set at 14atdc and 20btdc like the book says now you say to go to 10 btdc at 1200 on the hose at idle and finish at 24 btdc wide open.

I quess I should say, THIS IZ WHAT I WOULD DO!!!.....I hate to tell U to do sumpth'in an sumpth'in goes wrong, then Ya gunna blame me fer it....So, lets refraze this...I have run these time'in setting with NO ill effects!!!...

Now, On that heavy a bote, a long tuner will probablly do ya better than the 200 for bottom end, especially with the lower comp heds....

The bottom end jets(whcarbs) are air bleeds, so ya go bigger to leen(gives more air!!)...If the top end iz too rich, go smaller on the jets, and only go down .002" at a time, AND az U go down on the high speed jets, the idle will also leen without any jet change!!....Change'in idle jets are safer than play'in wit high speed jets, so if the idle iz the only thang U wanna change, then juss change tha idle jets....But if the top is too rich, then make the change...

Once U bump up the idle time'in(if U so choose) the higher time'in will cleen up the cyls sum...but will bump up the idle rpm....

U also kan try a 4 blade prop...

[vmax80096]

Thanks for the input T-REX, I was just making sure on what you were telling me.....I will bump up the idle timing first before I do anything to the idle jets and see what that does. I'm not going to touch the main jets or the heads, I use the boat mainly for skiing and thus will also stick with the stock tuner instead of going to the 200 tuner. It is my understanding that mine is longer thus more bottom end than the 200 tuner. I have boyseen reeds, perhaps they do something to the idle jets??? Once again, thanks for your input.

[vmax80096]

Well, had the boat out the other day...ran fine, haven't got the timing changed yet but that is next. Reringed it using sierra rings and a 1 piston got mercury rings...the mercury has 10lbs more, did I go wrong not using all mercury or will the sierra rings just take longer to seat in? Honed using a 400 grit stone. Cylinders and pistons were all within spec.

Did a leakdown test with a gauge that I have and the mercury ringed cylinder was 12% and all the sierra were around the 30%. I have only put on about 1/2 hour running time. Question is will it get better seal with more running time or should I have used mercury rings all around????

PS did a leakdown test on my brothers xr4 and his were all around 12% on a motor with about 200hours on it. Don't want to do it all again but if I have to so be it...this time with mercury rings!!!!

[T-REX]

i don't thank it's rings.....I use Pro rings all the time and they seel az good az Mercury rings,,,,It'z hard to say juss what the problem be(not have'in hands on info)...wuz that cyls with the rings bored, or resleeved???....Sounds like it may be tighter specs than tha others!!...JMO

[vmax80096]

The cylinders were all just given a light hone with a 400 grit hone....just enough to get a cross hatch. They all measured well within spec and I checked the ring endgap before I put it together and they were all the same, again within mercury spec. To me just seems odd that the one with the mercury set of rings had 12% leakdown and the seirras have about 35%. Not sure what to do now, perhaps pull it down again and go with mercury rings and try again!