V4 1987 Looper Low Compression & Backfire In One Cylinder

Bosunsmate

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I might be inluck with a wrecker in Fraser area.

Further see photo showing a hose from the body, is that you were talking about from the impeller Bos?

Cool, wreckers know a lot of the tricks to getting them running cheap too.
I cant see a photo on this so il try and be a bit more clearer.
Like you say, the control valve has three connections.
I took from what FBullet said that one of those is pressurised from the impeller directly. For that to happen there has to be a hose from down in the LU area that has being blocked off, or otherwise there has to be a connection to it from the Midsection or something before it enters the head.
I wish i knew, hopefully FBullet or someone else can tell you where that third connection comes from, im sure the wrecker would know. Sorry Riley ive never come across this system before and ive done yamaha, tohatsau etc etc.
So im learning too
 

Riley C

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Dec 23, 2018
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Cool, wreckers know a lot of the tricks to getting them running cheap too.
I cant see a photo on this so il try and be a bit more clearer.
Like you say, the control valve has three connections.
I took from what FBullet said that one of those is pressurised from the impeller directly. For that to happen there has to be a hose from down in the LU area that has being blocked off, or otherwise there has to be a connection to it from the Midsection or something before it enters the head.
I wish i knew, hopefully FBullet or someone else can tell you where that third connection comes from, im sure the wrecker would know. Sorry Riley ive never come across this system before and ive done yamaha, tohatsau etc etc.
So im learning too

Totally fine Bos, I need all the help I can get.

Oh now I get what you meant. Here is a photo of the the current throttle and the pin is there? See the capped photo to the head also.

The wrecker want $55 incl post and hoses. Pretty good.

Ill take a socket set with me tomorrow as Im going skiing with the boys and don't want to overheat.
Thanks,

Riley
 

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Bosunsmate

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Totally fine Bos, I need all the help I can get.

Oh now I get what you meant. Here is a photo of the the current throttle and the pin is there? See the capped photo to the head also.

The wrecker want $55 incl post and hoses. Pretty good.

Ill take a socket set with me tomorrow as Im going skiing with the boys and don't want to overheat.
Thanks,

Riley

Excellent, excellent, the end of the tunnel could be in sight.
That pin connects to a little metal arm on the control valve, try and make sure the wrecker gives you that as well. The little metal arm has a hole on it that the pin goes through. Not impossible to make one yourself, but im sure you'd appreciate saving yourself one more task.
That capped photo under the head is exactly what i was wondering about, great shot and discovery, hopefully thats case solved on that issue then, looks like it will be.
Have a good time rooster tailing tomorrow. Plastic bags etc can block up water intakes so do always keep an eye on the temperature. I tell all people out on my boat to keep cursory glances at the tell tale
Do let everyone know how the install goes
 

Riley C

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Dec 23, 2018
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Excellent, excellent, the end of the tunnel could be in sight.
That pin connects to a little metal arm on the control valve, try and make sure the wrecker gives you that as well. The little metal arm has a hole on it that the pin goes through. Not impossible to make one yourself, but im sure you'd appreciate saving yourself one more task.
That capped photo under the head is exactly what i was wondering about, great shot and discovery, hopefully thats case solved on that issue then, looks like it will be.
Have a good time rooster tailing tomorrow. Plastic bags etc can block up water intakes so do always keep an eye on the temperature. I tell all people out on my boat to keep cursory glances at the tell tale
Do let everyone know how the install goes

Thanks Bos,

I'm waiting on the valve to come through the mail. Can't wait to get this temp up, I think it's the source of alot of issues. They must have had it rigged for racing where rev constantly over 3k. Skiing is alot of idling and would mean less temps, and ski revs around 4k.

Also found the issue why I was reeving out sometimes at corners and planing, it was a spun prop. Managing to pick up a 13x19 SST prop for $80. See photo below, shows big difference.

A lesson a can be learnt about allowing people to add oil to your fuel tank. Don't ever do it, even from telling him the mix my damn brother added 100% more oil than required to the tank, result rich overload. Thinking he was adding for a full tank and not half.

Worst thing is he didn't tell me until we got on the water. I then had to run through scrub to get to ute to flush with new fuel.

Had to flush and drain 40litres into cans. Safe to say don't need oil for another tank with his mixing ratio. Killed two plugs in the process and was misfiring. Had to decarb all over again. Would I also need to pull down carby's from gumming up? I added Wyns complete fuel treatment to tank hoping it would clear it out??
 

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Riley C

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90 k's sounds PBG for a donk with marginal compression numbers,
though can't tell what boat it is from the profile pic,

only comment l've got is the high wot figure @ 6800,
what prop have you got on the thing?

Hi Tassie,

I think the prop is a 12x15? But now I have put the 13x19 SST prop in, got it for $80.

When I look at the gauge it looked like 6800, but closer more 6600. I just read my power pack (CDI) is set to 6700, so it would cut it anyway. At least I know that now, I want to bring the revs down.

No need to do 90k anyway.
 

Tassie 1

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I've been following this but haven't got any thing to add other than the wot is normally somewhere in the 4500-5500 range l think,

yours seems high
 

Riley C

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I've been following this but haven't got any thing to add other than the wot is normally somewhere in the 4500-5500 range l think,

yours seems high

Would too small a prop do this? Hopefully the large one will lower it, couple with new lync and sync.
 

havoc_squad

Senior Chief Petty Officer
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Mar 5, 2011
Messages
693
Would too small a prop do this? Hopefully the large one will lower it, couple with new lync and sync.

12 inch x15 pitch is awfully small for a motor in the 120 to 150 hp range.

I think most 13 inch props fall into the 85 hp to 115 hp category.

120 hp to 150 hp probably fall into the 14 inch diameter category.

If this is a ski boat, probably 14x17 or 14x19 if the engine is strong enough. Otherwise it's probably 13x19 or 13x21. If it's a tired motor, 13x17.

Pontoons or cargo boats plowing water will typically require less pitched props.

There are several websites and resources that can provide recommended prop diameter and pitch based on hp, application, and boat weight/type.
 

Bosunsmate

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Yes id screw in the Max timing advance screw a bit more as you dont want those pistons sorching from having too far advanced timing, at least do that until you can check it with a timing light.
Haha i dont think ive ever let anyone do anything to my boat without me doing intense surveillance on them and someone else doing the oil mix- no way! You can try and be thankful that he didnt put in too little!
Itl be fine, just make sure you always use marine 2stroke oil as the aircooled (line trimmers/chainsaws) need higher temperatures to burn off. Used in a outboard they will not burn off and put permanent deposits in there, gumming up rings/exhaust extra.
 

Riley C

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Yes id screw in the Max timing advance screw a bit more as you dont want those pistons sorching from having too far advanced timing, at least do that until you can check it with a timing light.
Haha i dont think ive ever let anyone do anything to my boat without me doing intense surveillance on them and someone else doing the oil mix- no way! You can try and be thankful that he didnt put in too little!
Itl be fine, just make sure you always use marine 2stroke oil as the aircooled (line trimmers/chainsaws) need higher temperatures to burn off. Used in a outboard they will not burn off and put permanent deposits in there, gumming up rings/exhaust extra.

Bos,

See photo below.

I haven't touched the max timing advance or WOT stop screw at all, only the idle and lync sync. I would have thought I wouldn't need to touch it until the timing light?

Currently when going into WOT the max timing screw and WOT stop screw line up with the valves etc, so I assume if I turn the max screw down all would follow?? Mind you the stop screw is all the in...

Or are you saying this because the thermos are not operating yet?

Will screwing it in throw all the sync out? If not how much would you screw it in and should this be done during idle?

Thanks again.
 

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Riley C

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Yes id screw in the Max timing advance screw a bit more as you dont want those pistons sorching from having too far advanced timing, at least do that until you can check it with a timing light.
Haha i dont think ive ever let anyone do anything to my boat without me doing intense surveillance on them and someone else doing the oil mix- no way! You can try and be thankful that he didnt put in too little!
Itl be fine, just make sure you always use marine 2stroke oil as the aircooled (line trimmers/chainsaws) need higher temperatures to burn off. Used in a outboard they will not burn off and put permanent deposits in there, gumming up rings/exhaust extra.

Sorry Bos,

I get what you meant, for a second I thought you meant srew in the spark adjustment screw at the timing base. Ill screw in the spark advance when I get home, it drops the idle alot.
 

Riley C

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Dec 23, 2018
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Reed valves and crankshaft seals have NOTHING to do with compression in the cylinder !

Understood Race.

I'm at a loss to get that compression up. You mentioned earlier about Crankcase compression..?

I might exchange the compression tool for another at super cheap and see if that works.
 

Riley C

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That goes in the hole on the carb body at 6 o'clock position. It got ingested when engine was running. Check all 4 carbs as it could have came from a different carb...

Fatz,

Should I just get rid of these fitings, other carbs I have seen don't even have them. At the moment I slightly squeezed the tube size of them so they stay in the plastic hole without sealing them in and avoid being ingested again.
 

Riley C

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Ok guys the water control valve is fitted now. Can’t say enough about Hervey Bay Outboard Wrecking. Not bad pricing.

hopefully put to the test this weekend.
 

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Bosunsmate

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Sorry Bos,

I get what you meant, for a second I thought you meant srew in the spark adjustment screw at the timing base. Ill screw in the spark advance when I get home, it drops the idle alot.

I get mixed up with the terms too at times, especially the specific linkages. The one that drops the idle is your minimum spark advance (its got a technical name ive forgotten too), thats not the one im meaning. Im meaning the one that limits how far your spark can advance at full throttle, thats the one you need to put it in a bit.
It will reduce your top speed a bit. Why you need to do it now before you get a timing light is because if it is too far advanced at the moment your ignition MAY be too far advanced ie too early and this leads to premature detonation and heating up of the pistons and piston failure, so its important its always within spec. So the safe thing to do is to restrict your top speed a bit now and preserve your pistons by reducing the spark advance until you can check it with a timing light.
I keep mine even a couple of degrees below what the specs call for as im the type of guy who warms up a car before driving it too
 

Bosunsmate

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Ok guys the water control valve is fitted now. Can’t say enough about Hervey Bay Outboard Wrecking. Not bad pricing.

hopefully put to the test this weekend.

Wreckers are great, know more than the pro shops often too.
Will be interested to hear how the temperatures and idle go. Hopefully you can drop the rpms down below 900 when she warms up and just use the warm up lever at the start when shes cold
 

Riley C

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I get mixed up with the terms too at times, especially the specific linkages. The one that drops the idle is your minimum spark advance (its got a technical name ive forgotten too), thats not the one im meaning. Im meaning the one that limits how far your spark can advance at full throttle, thats the one you need to put it in a bit.
It will reduce your top speed a bit. Why you need to do it now before you get a timing light is because if it is too far advanced at the moment your ignition MAY be too far advanced ie too early and this leads to premature detonation and heating up of the pistons and piston failure, so its important its always within spec. So the safe thing to do is to restrict your top speed a bit now and preserve your pistons by reducing the spark advance until you can check it with a timing light.
I keep mine even a couple of degrees below what the specs call for as im the type of guy who warms up a car before driving it too

Thank Bos,

Ok I will adjust this, bit daunted without the manual though. I will to get another as the Seloc was terrible as online version and I received a refund from Marine Engine. I do have a older overall manual but doesn't cover loopers very well.

Does anyone have online PDF versions of Loopers, I could purchase from them?
 

Bosunsmate

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Dont spend more cash, your accountant must still be totalling it up.
Heres the Joe Reeves method, its so successfull that you just type in his name in google and it prompts you to his timing method.
Have a read and post if you dont understand anything, may be Joe himself will answer your question.
Moderator The odd thing is this isnt in the sticky files, i found it elsewhere
https://forums.iboats.com/forum/engi...ming-procedure
 

Riley C

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Dont spend more cash, your accountant must still be totalling it up.
Heres the Joe Reeves method, its so successfull that you just type in his name in google and it prompts you to his timing method.
Have a read and post if you dont understand anything, may be Joe himself will answer your question.
Moderator The odd thing is this isnt in the sticky files, i found it elsewhere
https://forums.iboats.com/forum/engi...ming-procedure

Thanks Bos,

I have returned the compression tester back to Supercheap. Also got full refund from Seloc for the terrible online manual. She's starting to be a little happier. She might be even more happy if I sell my US Fender Telecaster so she can get a phone, which she actually needs lol.

I'll read Joes method, my mechanic is lending the 12v timing light and comp. See how we go, hopefully we are on a winner soon enough.

Thanks again.
 

Bosunsmate

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haha thats some impressive control over the budget you have
Check the firing with the timing light in that range when you hear a slight knock too. Hopefully the new control valve means temp is now right and the knock goes but while you have the light check there is no double firing on a cylinder around then. Timing lights take a bit of getting use too but theres a lot of info on you tube etc about double firing.
And go on sell the guitar, buy some bagpipes like me
 
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