Motor boggs down after on plane

[duhn]

I took the boat on a 30 mile run. One mile before our destination, the motor bogged down an I had to throttle down before it stalled. Sat for a minute then it ran fine. As the day progressed, it started acting up more frequent. It got to the point where I can only go 8 knots. It definetly was not running on all six cylinders. When we shut it down and sit for a couple of minutes it is able to get up on plane. Like something was cooling down. The block was not hot to the touch. At some point pee hole has a weak stream, it wasn't consistant with it bogging down.

The motor is an 86 blackmax 150 hp. thanks to this website, I was able to ressurect this motor from the grave last year.

I'm sure it's not fuel, because I took off the cover and can see fuel flying into the barrels while it was bogging down.

One mechanic said that it is not the coil because either they work or dont. Then he started asking me how many cylinders it was running on and which ones were running. I told him my fishing pole and tackle box are not capable of telling me that information. He wasn't ammused. He had mentioned stator, trigger or power packs in that order. does this stuff act up when it gets too hot?

Someone else mentioned that it was the impeller. HUH? The motor is shutting down because it is getting too hot. Last I checked, there isnt any electrical communication between the impeller and the ignition system.

Sorry for the long post. I am trying to answer any questions before they are asked.
Any suggestions would be appreciated.

 

[chrishayes]

Re: Motor boggs down after on plane

good luck, interested...

 

[Vlad D Impeller]

Re: Motor boggs down after on plane

It definitely does seem to be something electrical, your tech may be on the right track, at times a simple un-noticed loose connection in the wiring can produce the same symtoms that you're experiencing.
Don't rule the fuel tank ventilation either.

 

[Rowroy]

Re: Motor boggs down after on plane

A couple things come to mind:

1. I would not rule out the possibility that you sucked some trash into one or more of the carbs.

2. As previously alluded to, a temperature-related electrical failure. I would check the stator, power packs and trigger with a DVM/VOM as per the manual. Then I would heat them up with a heat gun and check them again, noting any difference in reading.

3. You need to get a new tacklebox and fishing pole - the kind that can help you troubleshoot your engine issues.

 

[Chris1956]

Re: Motor boggs down after on plane

Your symptoms lead to several ideas. Why not start narrowing it down?

Perform a compresion test. Compression should be 100PSI+ and even.

Lay out the spark plugs and notice their color. Black or oily are signs of fouling. White or green is sign of overheat, clean is sign of water intrusion. You want brown to dark brown.

Put a timing light on each plug wire and crank the motor. All should have spark.

See if pumping the primer bulb cures the stalling. if so rebuild fuel pump. if bulb goes flat, check antisiphon valve in fuel tank for debris.