Hey guys I have a 90’s model 135 mariner on a 16’ stratos. I can not get my boat to plane for nothing. I’m at a 21p was at a 18. I have cleaned the carbs check my reed valve. My motor runs like a top but when I try to plane off it bogs. Motor is trimmed down all the way and I am full throttle. There was a couple of times where I got it on a plane from a friend of my jumping on the bow repeatedly. Any help is appreciated.

If and wouldn't not plane with an 18" prop, it dang sure was not going to plane with a 21" pitch prop.  The higher you go in pitch, the harder it is to get on plane.

 

However, I would think a 135 on a 16" hull would turn a 21" pitch but not if that 18" was a good prop and it wouldn't get on plane with it, because it should have shot out of the hole with and good 18" on it.

 

So, that boils it to hull/setup problem or a motor performance problem.

Funny thing about a two stroke motor, you can have a cylinder not firing and you not realize it.  Do a compression test and check the plugs after letting it run hard at full throttle trying to get on plane, but don't let it idle before you check them.  They might still be black, but none should be wet.  As for the compression, I don't know what the 135 merc should have pound wise, but probably around 100, the main thing is there should not be any more that a 10% variation between the highest and lowest reading.  A good motor is going to have less than 5%, more than 10% means it's rebuild time.

 

Another issue, the early Stratos boats had open cell foam in them that was prone to become water logged.  I had an 89 285 Pro, I took of 300 pounds of wet foam out of.  See what the dry hull weight of that boats supposed to be, add the weight of the motor, batteries, and gear (but try to take as much as you can out of the boat) in it and have it weighed.  make sure you are not too heavy.

 

I have a hunch it's going to be more of a motor problem than anything though.  Even with an elephant in it, that 135 with an 18" prop should have gotten it on plane.

 

I understand the 21p was not gonna help the stress but after cleaning carbs and a couple small gas leaks the motor ran a lot better with ears hooked to it. So I changed the 18p to the 21p because I knew it needed it. My boat runs amazing out of the water. But once you put it in the water and try to plane it off it acts like the prop is ways to big just will not get out of the whole. I do see that one of my plugs had a misfire due to the black residue around the plug I’m not sure if that could be cause a problem or not

Another thing  that may not be helping is I did almost sink the boat a while back before the motor started acting up. My hull got full of water due to a airiator hose busting and water was flowing in the boat without my knowledge. The boat just about sank in 20 min. I made it back to the launch let it drain fixed the problem and took it back out. It ran fine after that but not long after this happened this problem came about so maybe the foam is full of water and making it have trouble getting out of plane. But it would make no since because the boat does not sit low in the water it sits about normal 

It can run like a swiss watch on the hose, that basically mean nothing, other than it will run.  Even at 2,000 rpm on the hose, (the max you should ever turn one not under a load) the motor is only running on timing, the carbs are not even open or if so just barely cracked.  That's why shop usually have a dino or a tank with a test prop, so the motor can be loaded and turned to max rpm.  The motor could have a bad high speed stator and you would never diagnose that on a hose.  Sometimes the trigger modules will work fine at idle and low rpm, but start breaking down under a load.  Also, mercs are kind of tricky getting the carbs right, so unless you really know them, it's very good chance about all you have done is take them apart, somewhat cleaned them and put a dirty carb back together, that has not be balanced with the others.

I would suggest you follow my recommendations if you want to diagnose the problem or take it to a shop that has the know how and equipment.

 

If you have a 16' 1990's vintage Stratos bass boat with 135 hp V6 Mercury/Mariner it may be over powered.

Your boat has a narrow transum width under 80" and the OB weight is going to push the bow up making planning difficult. 

Going up in prop pitch reduces lower rpm torque like trying to ride a bicycle uphill in high gear. 

Do you have a tach? What was the rpm with 18' pitch prop on plane?

Tom

I found out the problem with the boat after trying a lot of things y’all said. I had my compression tested 100 on all cylinders but one it had 75 so bad motor. 2ns time replacing it I guess I’m buying bad motors ran out of money to keep buying motors so looks like it will be a while before I get another boat thank y’all for the help?

Low compression doesn't mean the engine is ruined. It means that cyclinder needs repair, usually a burned piston from running too lean or not letting the engine warm up and oil the parts before running faster. A lean problem is easier to repair then metal to metal damage that can require a new sleeve, piston, possibly a rod and crank shaft repair.

You can pull the spark plug and visually inspect the top of the piston and cyclinder walls with a bore scope or have it done.

Why did you buy the 135 hp V6 for your 16' boat?

Tom

I bought the motor cause my boat came with one that I had no clue had a cylinder looking compression in it(I was young). The motor blew up about 2 moths later and I found this one for a steal. My dad passed away in 2015 at 39 with a heat attack we fished 24/7 and I miss it so I was just trying my best to get back out on the water. My boat is rated for a 140 so I didn’t over do it. I do have a good question though how much do you think it’ll take to fix my boat 

Without knowing what is wrong you can't ball park a figure. It's running so probably isn't too major like rebiulding the power head, just a piston and I believe a cyclinder sleeve.

Whenever I estimate something it turns out about 25% low, it always cost more.

Merc/mariner V6 uses the same weight engine for 135, 150 and 175 hp. The inline 6's are a lot lighter, it's the weight that can make difficult to plane but hp should over come it.

Have the engine inspected.

Tom

Yes sir do you think it will be any more then 2000 I found the same motor for 2000 ready to go with all cylinders at 110? What is the better decision