Testing engine

[JasonB]

I am tracking down an engine mist that only happens above 32-3400 rpm. unfortunately, the lake is 1hr away, which makes testing difficult. The engine is a Mercruiser 888. I don't run it above fast idle on the hose. Would it be reasonable to remove the prop and put the drive in a 30 or so gallon tub with a hose running full pressure into it so I can run the engine up to the needed rpm for no more than 5-10 seconds? Will running the engine briefly at these speeds without load hurt anything as long as teher is enough water for it to draw in?

 

[Reel Poor]

Re: Testing engine

Trying to run your engine without a prop like that would be the same as just reving the engine in neutral. For the miss to show up the engine may need to be under a load. <br /><br />Have you checked the points?

 

[JasonB]

Re: Testing engine

No points, converted to electronic module a couple years ago.<br /><br />Understand about load, just trying to isolate the problem a bit more and see if I can replicate it without dragging the bot to the lake.

 

[Haut Medoc]

Re: Testing engine

I don't think it will hurt it.....JK

 

[Bondo]

Re: Testing engine

Unfortunately,........ It's a Load Induced Problem.........<br /><br />Whether In Neutral, or the Prop Off, or even the Drive Off.......<br />It's All the Same........<br /><br />While I think the motor Will Survive the ordeal,........<br />I Don't see Any diagnoistic Value................<br /><br />Btw,......<br />What's the Recent History on your Fuel System,..????.........<br />It sounds like a Fuel Delivery Issue to Me.............

 

[JasonB]

Re: Testing engine

Carb was rebuilt last season and ran well for a couple months. I did pull the intake manifold late last season to install a new intake adn carb, but ended up putting the original back due to a poor fit with the new manifold. Used all new gaskets. <br /><br />The only lasting change from the intake ordeal is that I went to marine grade rubber fuel hose because the original metal hose was shot.<br /><br />The boat was running way rich so I adjusted the float. It still runs a bit rich, but is better.

 

[Don S]

Re: Testing engine

What have you done with the ignition system? You could have bad spark plugs, cap, rotor, points, condenser, plug wires, week coil or timing advance not working point dwell way off.

 

[JasonB]

Re: Testing engine

Will be replacing plugs this week. The wires were installed at the same time as the electronic ignition. It has a brand new cap and rotor (tested with old ones and it didn't help). Coil was also installed new with electronic ignition. Dwell is set by the electronics, but I have wondered about the advance. Base timing is right on 10 deg. The distributor on the motor is original 1976, but seems ok. I have another that looks almost new taht I bought as an extra.<br /><br />The engine also tends to warm up an additional 20 or so degrees above normal when the miss starts.<br /><br />I have also replaced the fuel filters.

 

[rob935]

Re: Testing engine

just give it a good service and test it on the lake...taking prop off is def. a waste of time.