87 Mercury 150 XR4. Engine trouble. Help!!

[Blb2003]

So I have had this boat for 10 years. And it has always ran like this and no one seems to know what the problem is. I have had it to 3 shops and everyone says it is fine.
Here is my issue. At home boat starts and idles fine no issues. When I am at the lake it starts and idles fine. But as soon as you get it in gear at neutral speeds it will start cutting out and die. If I go right past that to a little throttle It Will pull and run out fine. So idling up to a dock or anything it just dies. It’s takes the cold start throttle to get it started back and it runs rough for a bit but eventually clears out and I can put it in gear And take off if I throttle it quick. Has started running rough about 1/2 throttle and cutts out like a miss at idle. I have cleaned carbs new fuel filter, new plugs, new fuel pump. Checked and replaces vacuum lines. shop says it is in time and compression is good Idk what to do with it. Please help!!

 

[Faztbullet]

Bleed check valves been cleaned? Engine height? Exhaust reliefs buried?

 

[Blb2003]

Check valves? And exhaust reliefs are out of the water. Only by about 3-4” but out. I have tried pumping the bulb and choking it when it runs rough and it just kills it faster. It may be to lean? Kinda acts like it is loading up in neutral. And another weird question. When i take the carbs off should I be able to see the reeds? Or do I need to go further in?

 

[racerone]

You will see the reeds with carburetors off.----Need to post actual compression numbers here.----Check fuel pump.-----Perhaps test run with another tank and hose..

 

[Blb2003]

Checked compression today. All at 122. Took Lower unit off today to change impeller(haven’t changed in 5 years). The driveshaft was covered with exhaust tarnish. I’m assuming exhaust is leaking into the water side. I doubt that as anything to do with my problem but i have heard that a little silicone can fix that problem. I’m leaning toward it being a timing problem. Not sure how to check it properly.

 

[Faztbullet]

The check valve as in the intake and has the small rubber hoses hooked to them( ones you call vacuum lines). Remove hose from valve when running and it should be a fine mist expelled. If its more solid and drops valves need cleaned/replaced. Exhaust build up on shaft is normal.

 

[Blb2003]

Thanks for the response guys. I will check the check valves tomorrow. Got the impeller in today with new housing. Running here at the house my water psi is jumping from 3-10 psi. Haven’t seen that before. What should it run hooked to the hose? Racking the throttle it would bounce between 5-10 on decel. I just assumed it would be higher. Now for the check valves. Are they on the intake beside the carbs? I believe there are 2 on each side. Are there any in the case that I need to check?

 

[Dukedog]

might wanna check tha stabilizer/advance module also..

 

[Blb2003]

Checked all the check bleed valves today. All seem to be working. I cleaned them out and reinstalled. The only valve that was dirty was the one on the breather box. Not sure what it’s function is? I am assuming it has something to do with vac. But it was completely clogged, cleaned and reinstalled. Also reeds look good and tight. Will have to wait till Friday so I can put it In the water and see if it helps since it always runs good on the hose.