87 150 Mercury black max struggles to get on plain

[Turb0phish]

My problem is my motor starts and runs ok but alittle rough. When I go to get up on plain its bogs and strugles then shoots off and runs like a champ. Also my primer bulb loses some of its tension doesn't go completely soft but I can pump it a few time to get it hard again. Also the boat tends to run hot I can't putt down the river or it will get hot and today running down the river didn't seem to cool it off much and I've got a good strong steam coming out the back. I've replaced all fuel lines and fresh gas put in today. Oh and new plugs

 

[Chris1956]

Well, if the motor is tuned properly, maybe you have a prop with a to tall pitch. What pitch prop and what length and type of boat? What is compression on all cylinders?

The overheat is a problem. Time to test/replace your thermostats, poppit valve and water pump.

 

[Turb0phish]

Hi Chris thx for the response.
It's a 87 Cajun 18.5 fish master Paul Elise tournament edition it has a quicksilver SS 23 pitch prop.
I had the water pump done less then 40 hours ago. With the amount of water comeing out of the prop and pee hole I'm leaning towards the thermostats I orderedsome today. Fuel pump was rebuilt 60 hours ago. And it has between 120-122 on all cylinders. As far as tuned right goes I'm not to sure it idles a little rough and has a lot of trouble at low speed/ trying to get on plain after I get it out of the water it runs like a sewing machine at anywhere from 35mph-70mph. It's smooth as glass.

 

[Chris1956]

Some of those older V6 motors had fixed idle jets. They need to be clean for the motor to accelerate well. If you have a motor with adjustable idle jets you could richen them a bit and see if it helps your acceleration.

A 23P prop is probably OK, but if the motor is down on power, it will contribute to the slow acceleration.

 

[CharlieB]

Have you tested for a 7/16 inch spark on ALL cyls?

Checked WOT timing?

Either one wrong can cause overheating and poor performance.

Verify and repost.

 

[Turb0phish]

Ok so I found a no spark on #6 did the tests it was the coil I replaced it motor seems to run much smoother so we took it to the water. Started ok then when we got away from the dock I punched and it still bogged alittle but quickly jumped out of the water so a minor improvement or so I thought. Around the first turn there where kayakers so I drop the boat and putted by them after I was pasted them I tried to get up on plain I couldn't even get it to go by this time it was up to temp maybe alittle warmer it booged and shook it wouldn't do anything.
So we turned around and head back to the dock half way there we stopped to fish and let the motor cool.
When we finished fishing that spot we went to start the boat wouldn't start the bulb was empty (brand new) pumped it up and went to take off had same results as the first attempt. Bogged slightly then took off got back to the dock and sat and waited for people to unload there boats. By the time we could move again bulb was empty. I figured I'd try it again so I pumped the bulb and floored it dident do anything so I backed off the throttle some and it took off.
I have not checked the timing not really sure how have a good idea but not completely sure
P.s. I put new thermostats in. Guess that wasn't the over heating issue gonna replace the poppet value next.

 

[Turb0phish]

7/16th spark? You mean the gap? My boat has the flat tip plugs in it

 

[Turb0phish]

So just messing around with that fuel issue I noticed I can just pump the bulb and get small amounts of fuel go into to top and bottom carb. My guess is fuel pump fail or my floats are stuck?

 

[Chris1956]

The check valves in the primer bulbs are cheap. When the bulb is full of fuel. pinch the hose and squeeze the bulb to force fuel into the motor. If that helps, replace the primer bulb. Watch for air leaks in the fuel line, as they will cause engine to lose prime. if the carbs overflow, they need attention.

 

[Turb0phish]

Ok so the fuel connector gasket was worn out. Next the leaking fuel I was talking about is from the bowl vents witch I read is normal? My next question in an effort to maybe save alittle time and money is if I just fill the bowls with carb cleaner and let it sit awhile then drain the bowls and do I high concentrate of sea foam 1.5gal and 2 bottles of sea foam run through the carbs followed by a new set of plugs should clear up any carb issues. Or am I hoping for to much I've watched a few videos on the treatment that show great results but the filling the bowls part I only found one info and it was on a old car

 

[Chris1956]

Well, your plan will probably fail, because there are idle passages which are higher up than the level of fuel in the bowl. It is best to remove the carbs, soak them in carb cleaner, blow out the small passages and replace the floats, inlet needle and seat and all gaskets. Set the float height and drop.

 

[Turb0phish]

Hey Chris.
Sorry dident respond sooner (out of town) your right not gone half ass it so I ordered the poppet valve kit water pump rebuild kit that has everything in it fuel pump rebuild kit carb gasket kit needle valves floats fuel filter should be here Friday so I'll work on that this weekend hopefully it work. Gonna take it Monday to the local mechanic and have them tune and check the timing hope this works or it's getting a for sale sign. Lol

 

[Turb0phish]

So I replaced my impeller kit today. Took the boat to the water now it's bairly peeing out the back but the temp gauge took 4-5 mins of running to just get to the first line off cold with not much of a stream comeing out the back I shut it down and brought it home. Any reason a new pump would pee half as much as the old one but seem to keep the motor cooler?? Thinking maybe the gauge might not have bin working right if there is no water running through the block when I got up the ramp I open the cover to the motor and it wasn't very hot I could hold my hand on it was pretty cool so I'm confused now lol did I do something wrong or is that just how it is sometimes? The old pump peed like a hose this ones like a old man misty stop and go ****. Lol

 

[Dukedog]

all normal... t-stats are workin' as they should be....

 

[Chris1956]

A lot of those V6 motors will not have a telltale, until the thermostats open. However, you should have a strong telltale under load.