89 Merc Laser 220 XRi - fouling or over-oiling

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Don't understand about tha BU8H. Thats what it came with. Shouldn't have any effect on tha analog ecu. Got me a little puzzled. Have ya tried a BUZH?

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

John; I'll give the engine builder a call next week to ask if he "lapped the cages"

I assume this is the mounting surface the reeds fit to? and if they're not lapped smooth there can be air leaks?

The thing is, when the engine runs well (as it did last week) it runs awesome. After I tried Faztbullet's 1mm hole trick, the engine ran nothing short of perfect, no smoke, idled beautifully, awesome throttle response (hot foot) and had massive power (kinda scared the s**t outta me ). This was the best it had run since I've owned it. Funnily enough it was on the BU8H plugs. I will check up on this reeds question with the guy up north tho.

Duke; the plugs that came in the engine were BUZ8H, first time i replaced them I was told to stick to BUZ8H by the guy that built the engine. This time i visited the local merc guys and they said to go BU8H, even when I questioned them about ECU interference, he said "if you're not playing an ipod or listening to a stereo they'll be fine."

...Anyway, back to the shed

 

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Just thought it was strange. We've run BU8H's (BUZH's over 7 grand + motors) in everthing we own or built (except for digital ecu motors) for upteen years with no problems. Anyway GL and keep pluggin'. You will find it I'm sure..................

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Cheers Duke

So far i've done all the grounds on the port side of the motor, found a few that were in quite bad shape and poorly routed. There is a sensor on the port side head at the top, big hex shaped thing with a single contact, its unplugged and the lead is taped up - I'm thinking it might be a knock sensor? should i plug it back in?

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

OK this looks promising. I replaced all of the sketchy grounds i found and routed some to to the job better. The worst ground lead i found was from the 2 black boxes on top of the port side head, not sure what they are but there is 3 in total. The 2 im talking about were grounded thru the steel plate that separates them, then thru a lead from there to the block. This cable had only 1 or 2 copper strands still intact. I also made up replacement ground leads for all 6 coils as they were looking pretty tired and corroded.

After this i went around testing continuity wherever i could to check the ground leads were doing their job, seems good. Ill try to take it out for a spin tomorrow.

I also connected the ?knock sensor? back up. Let me know if there could be a good reason it was disconnected.

I'll post back the results

Gene

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

sonofabitch

just took the boat out, ran bad again. Same old story though, idles fine with engine tilted up, runs like crap when you drop it down, wouldn't rev, couldn't get boat planing, lots of smoke when stopped and free-revving.

There's a couple of other ground leads i might replace under the switchboxes yet, they really look ok though. Back to the drawing board

 

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Just lookin' back over this thread. Noticed you haven't mentioned tha ecu. It needs ta be checked, especially tha MAP sensor circuit. Its and older analog ecu and can have its problems.
One other thing is tha reeds. If they are gapped open, bent or broken it will show tha same symptoms..................

 

[Faztbullet]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Check MAP hose as Dukedog suggests and if ok double check the engine temp sensor, as if defective or loosing contact with cylinder head the ECU will "richen up" if it thinks its running cold. Also if you have a detonation module disconnect the grey/wht and retest just for giggles as if bad or receiving "knock" it will retard timing and add fuel. I am leaning towards fuel problem such as: intermittent TPS, busted diaphram in fuel pump or VST float not closing and fuel spilling into manifold, this may explain why tilting it up it runs good as float shuts off earlier.

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Duke: I'm kinda praying it isnt an ecu fault haha... but thanks I have made sure the map sensor hose is in good shape and sealed well. The reeds looked like new when i had the manifold off, to my eye they seemed to have a very strong seal/spring.

FB: There does appear to be a detonation module, and the white/blue wire was disconnected from the sensor in the port head - any idea why? I tried to call the engine builder but he's away till monday. It ran worse today with that sensor plugged back in - may or may not be related.

Fuel pump diaphragm has tested good (holds pressure well, cant squeze prime bulb). The VST is one thing i want to pull apart to check the operation of that float.

 

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Have you got a manual/test equipment or is just "backyard" testin?

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Have you got a manual/test equipment or is just "backyard" testin?

"Backyard Testin" for sure.

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

TPS voltage output is constant at 7.55v... with the sensor off the motor, turning it right around the output doesnt change... think i've found it guys - thanks so much for all your help - ill replace it and post up the results when i can