87 8hp Sailmaster quits

[airboat86]

I a have a 1987 8hp Sailmaster that sat idle for a year. It had been properly winterized and fogged before storage. It started with nary a tug and ran great for about 15 minutes. I noticed it started to sound like it was surging at high speed (just a bit). I ran it for about 25 minutes and when traveling at a moderate speed, about 1/4 throttle the motor lost rpm like I turned the throttle down and subsequently stalled. It did not sputter at all. The motor restarted with a single prime and ran great for another five minutes at what point it started to die again. I was able to counter the stall with more throttle and afterwards it seemed fine. What the heck is going on? Sticky float, airleak, clogged screen? Why is the problem so intermittent?

 

[Daviet]

Re: 87 8hp Sailmaster quits

Could be a restriction in the high speed orifice, sticky needle/seat, restricted screen on the fuel intake in the tank. Might be time to overhaul the carb. Are you running fresh gas?

 

[airboat86]

Re: 87 8hp Sailmaster quits

New gas, new tank, new primer bulb and fuel line. I found a small deposit on the lower part of the screen and cleaned that off. Pumped fuel through the fuel line and all seemed ok. It dies almost in 15 minutes consistently and always restarts with a prime. There is still pressure in the primer bulb when it stalls. I wonder if the primer could be the culprit.

 

[Daviet]

Re: 87 8hp Sailmaster quits

If it is running out of fuel and the primer bulb is firm, it sounds like the needle/seat is sticking. Have you cleaned the carb?

 

[airboat86]

Re: 87 8hp Sailmaster quits

Put some quicksilver cleaner in the tank today. Could it be the primer fills the bowl and it runs out without refilling? I thought there was a fuel pump.

 

[Daviet]

Re: 87 8hp Sailmaster quits

It does have a fuel pump, there is an early and late model pump. One bolts directly to the block and the other has a pulse line that makes the pump operate. If the engine will run properly by pumping the primer bulb, it sounds like a pump problem. On the pump that uses a pulse line, you could have a defective hose that operates the pump.

 

[airboat86]

Re: 87 8hp Sailmaster quits

That all makes sense now. The motor was running on the primer that wouldn't keep up with the demand for long. That would explain the smooth descending rpm before the stall. Thanks RA!

 

[airboat86]

Re: 87 8hp Sailmaster quits

Fuel pump is fine. The motor does not stall when running at high speed. The repair shop is at wits end trying to figure out what the problem is. The motor runs great in the test tank with a test prop on it using my fuel tank. I saw it run for almost two hours without a problem. When I put it back on my boat and ran it in reverse at the dock it died in two minutes. I ran it with no load and it did not stall. The shop thinks the exhaust baffle is choked with carbon and the motor is loading up under load. This might make sense, given the flat low speed power prop probably challenges the motor twice as much as the test prop they are using. Has anyone ever hear of this condition?