1994 Evenrude 88 spl" rattling"

[IH8JEEP]

I know this is a long shot but here gos. I have a 1994 Evenrude 88spl that seems to "rattle" like valve chatter. Seems worse under load before planing out. I was running(cheap gas) low test gas 87 10% ethenol and 50:1 oil. Do/can out boards "Knock,chatter" like trucks pulling load up hill on "cheap gas". Should I be running "good gas" 91 high test in my out boards. What else should I look besides wires,cables vibrating.

 

[SparkieBoat]

Re: 1994 Evenrude 88 spl" rattling"

non efi 2 stroke out boards do not have valves. so you may have a bearing or crankshaft problem..or you could have a timing issue...do a spark test with a spark gap tester..then do a compression test..and we will go from there. but it should not be rattling..and mine does not rattle with 87 octane %10 ethanol gas and 50:1 oil.

 

[IH8JEEP]

Re: 1994 Evenrude 88 spl" rattling"

non efi 2 stroke out boards do not have valves. so you may have a bearing or crankshaft problem..or you could have a timing issue...do a spark test with a spark gap tester..then do a compression test..and we will go from there. but it should not be rattling..and mine does not rattle with 87 octane %10 ethanol gas and 50:1 oil.

Yea I know 2 strokes don't have valves and I already did all the checks you listed and more. I'm not going to spend any money on this motor cause I plan to repower in spring. The motor runs great has low hours 99% fresh water use. I just want a bigger motor and don't want to burn someone on this one when I sell it. I guess I should have asked if you can HEAR a outboard detonation from low octane? And CAN a outboard have detonation from low octane?

 

[emdsapmgr]

Re: 1994 Evenrude 88 spl" rattling"

That engine should run fine on low octane pump gas. You might want to pull the spark plugs and have a look at the walls of the cylinder liners. A small penlight may help. You could have some cylinder scuffing going on. If you just can't see anything through the spark plug hole, you might want to pull the heads.

 

[SparkieBoat]

Re: 1994 Evenrude 88 spl" rattling"

I doubt your issue is fuel related

 

[Chinewalker]

Re: 1994 Evenrude 88 spl" rattling"

Check the easy stuff first - I've seen a few Johnrudes over the years that had loose cowling latches. The handles would rattle against the belly pan...

 

[wilde1j]

Re: 1994 Evenrude 88 spl" rattling"

The kind of noise you describe, especially if it came on suddenly, usually is a precusor to throwing a rod, or some other unpleasant event. Extremely unlikely to have anything to do with the gas you use.

 

[IH8JEEP]

Re: 1994 Evenrude 88 spl" rattling"

Thanks for comments I am still asking about detonation. I'm asking about if you can HEAR a outboard detonation from low octane? And CAN a outboard have detonation from low octane? My local evenrude marine shop in buisness 20+ years told me to only run high octane fuel in this motor. He said low octane fuel is DEATH for these OLDER motors. But most people on hear say run at least 87 octane but don't have to run the "good stuff" (89-above).

 

[SparkieBoat]

Re: 1994 Evenrude 88 spl" rattling"

I have run 87 octane which is the lowest available grade..in multiple 1980s, 1990s and 2000s model motors with no issues related to octane...make a video with sound and post it on you tube..then post a link..none of my motors have any type of rattling/pinging.

 

[wilde1j]

Re: 1994 Evenrude 88 spl" rattling"

Thanks for comments I am still asking about detonation. I'm asking about if you can HEAR a outboard detonation from low octane? And CAN a outboard have detonation from low octane? My local evenrude marine shop in buisness 20+ years told me to only run high octane fuel in this motor. He said low octane fuel is DEATH for these OLDER motors. But most people on hear say run at least 87 octane but don't have to run the "good stuff" (89-above).

If you were in a third world country, octane might be a problem, but not in the US. Any engine can have detonation, but you'd probably never ever hear it in any OB, due to ambient noise. 87 octane is fine for any motor, except a small number of racing motors not in the general publics hands. You will just waste your money and actually cause deposit build up using higher octane fuels.

 

[boobie]

Re: 1994 Evenrude 88 spl" rattling"

It could also be a piston rattle meaning a piston skirt that is colapsing. Those mtrs were noisey right out of the box but if you just started noticeing it, something is going on.

 

[James R]

Re: 1994 Evenrude 88 spl" rattling"

Try pulling the plug wires one at a time with the motor running to see if one or more cylinders are not firing. Rattles in these motors can be caused by one or more cylinders not firing correctly. I use a thick leather glove to avoid being bitten by spark volts.

 

[IH8JEEP]

Re: 1994 Evenrude 88 spl" rattling"

Try pulling the plug wires one at a time with the motor running to see if one or more cylinders are not firing. Rattles in these motors can be caused by one or more cylinders not firing correctly. I use a thick leather glove to avoid being bitten by spark volts.

I will try this. I can see it now "hey son put these gloves on"... son " eh..why..." old man(me)"remember when you wrecked my new Mustang GT....payback... oh and put this lifevest on before you get me another beer"

 

[Faztbullet]

Re: 1994 Evenrude 88 spl" rattling"

Rod or wrist pin bearing my $.02

 

[IH8JEEP]

Re: 1994 Evenrude 88 spl" rattling"

Rod or wrist pin bearing my $.02

I hope not. I would rather run her one more season or till she blows than sell something bad. I just keep dreaming about that big ol 150hp merc. with 125hp stickers I have paid for at the shop

 

[jonesg]

Re: 1994 Evenrude 88 spl" rattling"

You can check for connecting rod slop by inserting a dowel thru the sparkplug hole ,
rotate the engine past TDC,
follow the piston with the dowel(no pressure) and as it starts on its downward travel ...stop and press down on the dowel,
if theres slop in the rod you will feel it click as you press down.

 

[IH8JEEP]

Re: 1994 Evenrude 88 spl" rattling"

You can check for connecting rod slop by inserting a dowel thru the sparkplug hole ,
rotate the engine past TDC,
follow the piston with the dowel(no pressure) and as it starts on its downward travel ...stop and press down on the dowel,
if theres slop in the rod you will feel it click as you press down.

Thanks!!! I will do that and put that in the old brain as a do before buying a used/new motor and add to my check list when replacing plugs on all my motors each spring. Great info !!!

 

[emdsapmgr]

Re: 1994 Evenrude 88 spl" rattling"

Another scenario. As crossflow hours pile up, it is not unusual for them to get piston slap. Common on very high hour crossflow blocks. The cylinder walls start to taper and the pison skirts get out of round. This powerhead noise sounds bad, but is not necessarly a prelude to any imminent failure. It does say something about how worn the powerhead is, and that you would need to overbore it-should you ever plan a complete overhaul. That powerhead has extrememly low compression bathtub heads on it from the factory. It will easily run on any base gas sold commercially here in the US.

 

[surrender]

Re: 1994 Evenrude 88 spl" rattling"

On my 88 I hear a rattle when pulling the throttle back from high rpm's(5000 down to 2000) to fast(dont do it anymore unless taking an evasive maneuver) . When I ease the throttle back and come off plane its all smooth.

 

[wilde1j]

Re: 1994 Evenrude 88 spl" rattling"

You didn't say, but did the rattling come on suddenly, or did it always make the noise???