1986 75hp merc fuel hydrolocking???

[Jet tracker]

I have a 86 merc 4cylinder 75hp. Is it possible to flood out two cylinders and hydrolock with fuel and not water???

 

[Jet tracker]

I will try and be specific with the problem but this is strange, basically if I am firing the boat up cold with the throttle at 3/4 and choke on. It will roll just fine no problems but if it does not fire within 10 sec or so. It will gradually slow down and act like it locks up, or like the bat dies. If it let it sit and mess with it a little bit. It will eventually take eight back off and fire up. When it is warm and I start it with no throttle If it doesn't take right off it will do the same thing, I have two batt though a marine switch that both test out 12.6 volts, brand knew starter and starter cylinoid, all wiring has been pulled apart cleaned and check so I am not thinking this is electrical, it did recently reset the floats on the carbs which is y I am asking about the fuel hydrolocking the cylinders

 

[GA_Boater]

Have you pulled any plugs to see if it is hydroing?

 

[Jet tracker]

Well everytime it does it I'm on the water a mile or tow away from the launch so it is more concerning to me to get it fired and back b4 I end up stranded. But i am gonna take it out tomorrow and if it does it I'm gonna pull plugs. I'm pretty handy with this thing but this is extremely odd to me

 

[jimmbo]

While it is theoretically possible to flood two stroke to the point of hydrolocking it,I doubt the engine would crank very fast trying to move the fuel from the crank case to the cylinder, and most of it would end up going out the exhaust port to surround the boat.

 

[Chris1956]

A leaking fuel pump diaphragm can cause excess fuel into some cylinders. You would normally see lots of fuel on the water, as it escaped via the exhaust ports.

 

[Jet tracker]

I believe I'm gonna have to call the time of death. Locked up pulled plugs, still locked up, its deff internal. Thank god fo trolling motors as I'm in the process of the float of shame to the launch

 

[racerone]

remove bypass covers to have a look at the pistons.-----Did you mix gas and oil at 50:1 ?----Replaced water pump impeller recently.----Checked gear oil ?

 

[schematic]

Locked up engine can also be caused by a locked up gearcase. Check the gear oil for oil or lack of....Top gear case bearing likes to seize if proper oil is not maintained.

 

[Jet tracker]

This has a jet lower unit so gear case is pretty well out of the question unless the bearing in the jet unit froze up. Yes I mix amzoil 50:1 and the impeller is pumping water as it should. It did seem hot when I pulled the plugs tho. And I am debating on tearing it down right now. I was hoping there would be something simple but it's not looking good. I think I will start with taking the jet unit off and looking at the bearing but that has a direct grease fitting on it that gets grease every time it comes back so it is almost impossible for it to be froze up. I will take inspection covers or the head off after that unless anyone has another idea. I. Open for suggestions

 

[racerone]

There is no " cylinder head " on that motor.

 

[Jet tracker]

I'm sorry "cylinder block cover"

 

[Jet tracker]

Rock stuck in the jet impeller!!! Yes it was in the lower end!! Giant sigh of reliefe!! Thank you all for the help

 

[GA_Boater]

Good deal, JT! :smile:

Hope no damage1

 

[Jet tracker]

Nothing a grinder and a dremel couldn't fix. Need to replace the sleeve and the jet impeller anyways it's not the first time I have had rocks up in there just never had one wedge and jam it up