'88 Force 85hp exhaust boot split open. I need help identifying a plastic part.

[DunbarLtd]

Ive read couple other motors did same thing. Not sure what caused it or if it damaged anything but i hope not. That would suck.

You want plugs to be slighlty oily that just means its running a little rich which is preferable. But you want it running rich because of how far out the aur screws are not because theres a flooding issue. You could lean it out. Dont turn the screw in any further than 3/4 turn from lightly seated or itll run too lean and hot.

If you lean it itll idle smoother and the plugs should lose that oil. At least you will know if you have a flooding issue.

I would think if the air screw doesnt make a difference its tip is worn down and letting air go by but im not a guru by any means.

And it takes a trained ear to hear slight differences. Just adjust the screw either way til it chugs (too rich) or pops (too lean) and set it to halfway between the two. Turning them til it dies is fine. You may have to adjust several time to get it right so it doesnt die on you but chugs or pops. I read some guys start 1 turn out. Some 1 1/8 out and some 1 1/4 out. Im going to start at 1 1/4 and see how it goes.

It make take some tinkering and patience of course to get it right.

Also, I think doing compression test would be 1st thing to do. Thats always the advice i see.

Then make sure u have nice bright blue spark on all three cylinders. Make sure to ground the plug wires to the block.

Then make sure fuel issues are resolved. No leaks and diaphragm is good. Filters clean, No water in the fuel....

A link and sync is important.

Im new to these outboards so im still learning as i go but theres a ton of info on this site if you search around. The stickys at the top of this forum are full of good stuff. Hope you get to the bottom of your issue because i may have the same issue as you.

I havent taken it out but once since i replaced that boot and i wasnt too happy with it. It ran ok but definitely something seemed off. I should get it back on the water by this weekend. Ill take notes and come back with the results.

Hopefully its something minor. A full rebuild is not something i want to deal with.

 

[jerryjerry05]

I had the bang just like yours and tore/blew the boot wide open and when I replaced it, the engine was running like crud, smoking...my fuel pump diaphram was torn. So, I fixed that, but now when I'm on the water, it runs great away from the dock, but starts to chug like the fuel line is choking out, but the primer bulb is still firm and pumping it didn't solve any problems. I pulled my carbs off as they were leaking as well and gave them a good cleaning with carb cleaner..there's really not much to them. My idle needles are solid, no rubber tips either. Only my floats have needles with rubber tips ( and they seal perfectly ). I was hoping that maybe something clogged up a carb a bit when the diaphram had torn, but I'm not convinced of that anymore. I worry that that gun shot backfire has caused a leak in the block somewhere. I am planning on giving it a better look in the spring as the boat is winterized. Interestingly, when I was on the lake trying to tune the carbs, adjusting them lean never really raised the idle. It seemed like all I could do with the idle jets was kill the motor.

When I ran it out of fuel and the carbs started to run lean, the idle raised up expectedly. I'm thinking that I'm flooding the motor as everytime I've pulled plugs, they are slightly wet with oil...man, and it was running so beautifully before the explosion too...

​ANYTIME!!! you have a backfire that hard it splits the boot?? The other seals " cylinder intake port covers" they blow out and cause the rough running.
Do the starting fluid spray around the intake side and see if the gaskets are blown out too??
One tiny spot the size of pin head will suck enough air to destroy your motor.

​IF?? the air screws do nothing?? then it's sucking air somewhere else????

 

[jerryjerry05]

Ive read couple other motors did same thing. Not sure what caused it or if it damaged anything but i hope not. That would suck.

You want plugs to be slighlty oily that just means its running a little rich which is preferable. But you want it running rich because of how far out the aur screws are not because theres a flooding issue. You could lean it out. Dont turn the screw in any further than 3/4 turn from lightly seated or itll run too lean and hot.

If you lean it itll idle smoother and the plugs should lose that oil. At least you will know if you have a flooding issue.

I would think if the air screw doesnt make a difference its tip is worn down and letting air go by but im not a guru by any means.

And it takes a trained ear to hear slight differences. Just adjust the screw either way til it chugs (too rich) or pops (too lean) and set it to halfway between the two. Turning them til it dies is fine. You may have to adjust several time to get it right so it doesnt die on you but chugs or pops. I read some guys start 1 turn out. Some 1 1/8 out and some 1 1/4 out. Im going to start at 1 1/4 and see how it goes.

It make take some tinkering and patience of course to get it right.

Also, I think doing compression test would be 1st thing to do. Thats always the advice i see.

Then make sure u have nice bright blue spark on all three cylinders. Make sure to ground the plug wires to the block.

Then make sure fuel issues are resolved. No leaks and diaphragm is good. Filters clean, No water in the fuel....

A link and sync is important.

Im new to these outboards so im still learning as i go but theres a ton of info on this site if you search around. The stickys at the top of this forum are full of good stuff. Hope you get to the bottom of your issue because i may have the same issue as you.

I havent taken it out but once since i replaced that boot and i wasnt too happy with it. It ran ok but definitely something seemed off. I should get it back on the water by this weekend. Ill take notes and come back with the results.

Hopefully its something minor. A full rebuild is not something i want to deal with.

​The air screw on the carb: remove it and see if it's smooth and pointed.
ANY scoring or grooves and rounded tip means it's no good.


​To adjust an air screw.
​Set them at 1 1/2 turns out.
Some need to be 2-3 turns out??(another story)
Turning the screw in while running might kill the motor.

Get the motor started and warm.
​The in the water or in a deep bucket.The motor needs the back pressure from the water in the snout/exhaust.

​Start at the top carb.
Turn the screws in till they just bottom.
Then out 1 1/2 turns.

​Then turn the screw in 1/8th of a turn.
Wait 10 seconds for the new setting to take effect.
​Repeat until the motor kicks, bucks, stalls.
​Then back out 1/2 turn.
Do this on all the carbs.

​On the 120/125 there is an equalizer tube.
This should be pinched closed.

​This should get them running right.

 

[DunbarLtd]

Excellent jerry. Thank you for clearing that up. You read too much and you get overwhelmed because of all the different opinions.

I think starting with 1 1/2 turns out sounds good. Book says 1 turn out. LOL. But that seems like youd lean it out pretty easily from there. I will try the 1 1/2 like you say. Then adjust idle speed as well.

I bought a timing light i still havent used so ill static time it to 28 degrees just to make sure. I doubt its off but i need peace of mind.

Then i also installed a tiny tach. That should help get the idle speed correct and also check my wot rpms. I have a 15 pitch prop on now and wot seems to rev too high to me but i never had a 2 stroke outboard before so i definitely dont gave an ear for it.

The tach will help clear that up. Book says look for 4500-5500 rpm at wot.

One last thing....the new fuel pump diaphragm is paper thin and looks like just a smooth piece of rubber. The old one kinda has what seems to be reinforced (thicker) areas where it flexes. If that makes sense. Not sure if the after market diaphragms are inferior or not.

The middle port gasket came with fuel pump kit. It didnt look torn but like you said a pinhole can do damage.

The spray test should do the trick.

Thanks again for all the help.

 

[jerryjerry05]

These motors don't usually jump timing.
​The diaphragm IS a very slim rubber part.

​15p ?? The 15 is usually used on heavier boats and pontoons.
​Or can be used when pulling skiers and tubes.

What size boat ??? Load??

My boat had 17p props.
I thought I needed MORE!!
More speed, performance.

​I changed to 19p.
I got more.
3mph and my fuel usage went up 15-20%
So it's pretty important to have the right prop.

The 15 on a smaller boat can actually allow the motor to over rev.

 

[DunbarLtd]

Well thats exactly what i thought. I have the 88 17ft bayliner capri 1700. I actually removed the seat boxes while redoing the floor. Installed some fold up fishing seats.

Theres always me and a buddy and a large cooler full of ice and drinks, somewhat heavy toolbag. Extra starter battery up front for night lights mainly. No trolling motor yet still workin on that. Rest is just poles and lightweight stuff. We both weigh total of 430lbs.

20 gal tank which i keep full. I get around 33mph wot.

I had the prop repaired and they said it was a 15p. Id like to go up a few to see what happens. Also we never ski. Maybe previous owner did.

 

[jerryjerry05]

I would get the tiny tach first.
​Then go for a ride and see what the rpm's are at wide open.
I've been in that same boat and it should do closer to 40, maybe more.
I believe it came standard with a 17p ???

 

[DunbarLtd]

40 would be nice. Theres a prop shop a around the corner who fixed this 15p. Ill go over there and see if they have a loaner 17p.

I hooked the tiny tach up last night. I wish i knew beforehand they come with such short wiring but ill deal with that. Maybe even return it and have them add wire. Its only extra $10.

BTW for future reference the TT2AM tiny tach is what you want for an outboard. Their mechanic told me the "m" means it comes with a noise filter which is what you want. And that model is waterproof.

 

[DunbarLtd]

Took the prop in and its 13 1/2" 17 pitch apparantly. No idea why the other place said it was a 15p. Wont be going back there. They also didnt do good weld job and didnt cup the edge. This new shop should do a better job. The owner went in depth with me. Had a little physics lesson about cavitation....ventilation..etc..

Should be done by tmaro. Then i go test.

 

[jerryjerry05]

Just because the edge isn't cupped doesn't mean it's not a cupped prop.
It doesn't have to have a cup on the edge.

 

[DunbarLtd]

Interesting. He showed me a "cupped" prop vs mine and that edge on mine was perfectly flat. He seemed to be very knowledgable.

When he referred to cupping he only talked about the edge. Not the entire blade, which i assume is what you mean?

 

[jerryjerry05]

I know when I first learned (1989)about the " no cup,, cupped prop"
​I argued with the parts guy and he showed me the literature from the manufacturer.

​Something about the whole blade was cupped?????

 

[DunbarLtd]

I see. Well then maybe he was blowing smoke up my rear end???

He mentioned when you cup the edge you eliminate bubbles creeping around to the other side. Which is bad i guess. And then i suppose that cup also helps grab water better or is that a myth too?

But i do see what you mean. If the entire blade is cupped it should do its job. How much the edge makes a difference im not sure.

But he convinced me it should be cupped so i went with it. Literally every prop he had hanging on his wall, aluminum and ss, had the edge cup. I didnt want to get into a physics discussion so i just agreed and moved on.

 

[DunbarLtd]

Took the boat out today but winds whipped up quick so had to head in early.

I was able to spray test the engine and its not conclusive just yet because the wind and swells were crippling. Ill have to go out again when the weather calms down.

But it started and idled ok. Wasnt able to fine tune the carbs but it ran decent at 1 1/4 turns. Didn't get to WOT. Chop was too crazy. 3-4ft rollers. I will next time out.

The tiny tach was working. Jumps around more than i expected but it looked like in neutral is was around 750 800rpm. Didnt check it while driving. Cord is too short to reach the dash. I will sort that out later.

But it did die on us after we drove out into open water and let it idle in neutral. Maybe a couple minutes before it quit.

It started back up ok without issue. Im sure it needs fine tuning to keep it from dying or i have another issue to deal with.

 

[jerryjerry05]

The motor should be 750-800 in gear.
Neutral should be about 1100 rpms.

At 750 in N then it drops to 500 or so in gear???
That's why it stalled.

 

[DunbarLtd]

How would i increase idle rpms in neutral?

 

[jerryjerry05]

On the stbd. side, the towershaft.
At the bottom of the shaft is a screw and locking nut.
Back off the nut and screw in the screw.
The towershaft has the timing linkage at the other end.

 

[DunbarLtd]

I see it. When I adjust the carbs, that should affect idle so im guessing ill have to go back and readjust idle speed?

And Franks sticky is very elaborate and helpful as are all of his posts which ive been reading for a while. So i am sort of getting familiar with these outboards.

One tiny detail i think i didnt understand was about adjusting carbs.

Do i fine tune each carb one at a time or do you turn each carb in 1/8 then wait, then turn all 3 again and so on?

I know seloc isnt that great but it says do one carb at a time. Meaning turn it in and out and find that happy middle point...then move on to the next carb.

I havent the experience to know which way is preferred or does it even make a difference?

To me id want to see what the motor does when i adjust all 3 at the same time then readjust as needed rather than 1 at a time.

Whats your preferred method?

Id love to get a hold of an actual service manual. Ive searched ebay and see some for like $50 but not even 100% confident they are the correct manuals for my model which is 186X8A 85hp 1988.

Thanks again. Tomorrow looks super nice so hopefully i hear from you by then. Have a good one. I appreciate all the help.

 

[jerryjerry05]

One at a time.
​A manual from the 85-89 era will work for the mechanical end.
The 85-86 used a different ignition system.
​The packs and coils used a plug in instead of the screw down type.

Adjust the carbs then raise or lower the idle, then do the carbs again.

 

[DunbarLtd]

Ok i did spray test. I couldnt tell if motor changed so i dont think i have air leaks. Sprayed every gasket i could find.

The tiny tach went out after using only 10 minutes. And setting rpms that way seems impossible because the rpms were jumping around.

Maybe thats indicative of an engine issue?

I messed with it for half the day. Setting it and doing hole shots and idling around.

I ended up setting idle speed in neutral just so it wouldnt die and when put into gear it clunks a little. But if i lowered the idle speed any lower so it doesnt clunk it dies while idling or when put into gear. Seems like a fine line to set it.

I had a rough time doing the carbs but in the end i set them all to 1 turn out. Ill prob need to take it somewhere and hopefully watch them tune it and learn how to do it. I just dont have the ear for it.

However it stays running while trolling at about 3.5mph (gps).

The day was nice with slight breeze and minimal chop. With myself and buddy and cooler full i was getting 33mph max when trimmed. Again measured by gps. No idea what wot is because tach died too soon while settung carbs.

It is getting 16-17psi water(dash gauge) at wot.

Installed new thermometer while doing fuel pump.

I have a impeller kit and will do that next. Is 16psi good at wot??

When it started it coughed again a few times first thing when cold. Took a few cranks to get it going. But i had carbs set richer. Ill see what happens next cold start.

Out on the water after couple hours messing with it...it starts first crank. Occasionally itll cough but start very next crank.

Oddly if i choke it while cranking it doesnt cough. Actually i only tried that once out of curiosity. Maybe theres something to that??? Next time out and when engine is warm ill choke it everytime i start it to get a conclusive diagnosis. It shouldnt have to be choked when warm but if choking it every single time solves the coughing maybe that can help narrow down an issue its having??

Should i check compression now as it is because wot speeds? ??
Decarb????

Oh and i was curious if there is a gapped plug we can use on these outboards? The champion ul18v's foul too easily. I cant troll around for 10 minutes before they gumup and then doing a holeshot itll sputter. When i take them out and clean them it holeshots perfect.