1975 75hp johnson stinger 2 hard to plane

[edylina]

I'm new to this forum. Last year I was given a 16 foot 1970 glastron trihull with a 1975 75 hp johnson stinger2 outboard model number 75ESR75B. With the driver and 1 passenger the boat gets up on plane and cruises easily at 32mph. When another 2 adults sit in the back of the boat it bogs down and won't get up on plane unless 1 adult moves to the front of the boat to shift the weight forward. I ran a compression test top cylinder running 85psi middle running 90psi and bottom running 88psi. motor has no trim and has a dolphin installed no clue what brand. It's also running a 17 pitch prop. Any help would be greatly appreciated! Thanks in advance.

 

[joey nathan]

Re: 1975 75hp johnson stinger 2 hard to plane

Yeah, I don't really think your engine has a problem. Taking into account that it's 35+ years old; and 4 adults are going to weigh in the neighborhood of 800 lbs. that's asking a lot. A 17 pitch prop is probably the stock one that came with the engine and would give you the best chance at a good hole shot.
You're going to have to just move someone up front for a few seconds in order to plane out when that many people are in the boat.

 

[TJShag13]

Re: 1975 75hp johnson stinger 2 hard to plane

I have a '73 glastron trihull and my '72 65hp will plane with 4 people all in the back to back seats. You should check to maker sure your foam below deck isn't soaked with water weighing you down. I can ski behind the boat with 3 adults in it so there has to be something holding you back.

 

[sramos]

Re: 1975 75hp johnson stinger 2 hard to plane

I have a 1975 Tri-Hull and a 85 HP Johnson. Hard to plane when load down but will do it. Certainly easier with less weight or if I move someone forward. Not sure if its normal or not - for what its worth.

 

[yoster]

Re: 1975 75hp johnson stinger 2 hard to plane

Yeah 75hp I would think should be enough umph to get you on plane. What elevation are you running at? Higher altitudes can kill performance if you don't re-prop.

 

[boobie]

Re: 1975 75hp johnson stinger 2 hard to plane

Try putting a 15" pitch prop on it and check your hull to make sure it's not water logged. Hate to tell you this but those mtrs were dogs out of the hole. Been there.

 

[sramos]

Re: 1975 75hp johnson stinger 2 hard to plane

In my case - the boat is dry as a bone. No water at all. However - my prop is really dinged up. Not even sure what the pitch on it is. It could really use a new prop. Mostly running between 1200 and 1500 ft above sea level.

 

[boobie]

Re: 1975 75hp johnson stinger 2 hard to plane

I was refering to the 75hp.

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

running pretty much at sea level. there is floor damage in the rear of the boat that has been poorly repaired by a previous owner I was planning to replace the floor so while I am at it I will check the foam thanks! gonna pull the carbs and clean and rebuild them as well

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

I forgot to post when I ran my compression test it took a bit to get the boat to start and I noticed the fuel line was not sealing to the tanks so I have ordered replacement connectors for the fuel line to fix that problem. I'll post an update after I clean and rebuild the carbs and replace the fuel line connectors. I also didn't run the test at WOT and read some places that that can cause a lower compression reading?

 

[boobie]

Re: 1975 75hp johnson stinger 2 hard to plane

What about the prop? Did you ever change it?

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

I'm planning to do the carb rebuild and cleaning and replace the fuel line connectors then take it out for a day on the lake to see how it goes. if still lacking low end I'll be looking in to trying out a different prop

 

[stevo10081984]

Re: 1975 75hp johnson stinger 2 hard to plane

I forgot to post when I ran my compression test it took a bit to get the boat to start....I also didn't run the test at WOT and read some places that that can cause a lower compression reading" you shouldnt be running your motor while doing a compression test....am i understanding you correctly?

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

no the motor wasn't running during the test I had just read that the carbs should be wide open to let in as much air as possible when you run the compression test not sure if this information is correct or not?

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

iboats has mallory or sierra carb rebuild kits with floats. what do I look at to know which ones to order

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

I replaced the leaky fuel line connector today and the motor fired up without starting fluid after about 2 cranks. I noticed quite a bit of light grey whitish sludge that is coming out with the exaust is this normal or would this point to another issue somewhere? I took a picture but I'm not sure how to post it here

 

[rickryder]

Re: 1975 75hp johnson stinger 2 hard to plane

While doing a compression test all the plugs should be out of the motor. WOT I have never heard of......

 

[rickryder]

Re: 1975 75hp johnson stinger 2 hard to plane

running pretty much at sea level. there is floor damage in the rear of the boat that has been poorly repaired by a previous owner I was planning to replace the floor so while I am at it I will check the foam thanks! gonna pull the carbs and clean and rebuild them as well

Your poorly repaired deck could have some underlying issues... If water has gotten in you could have waterlogged foam,rotten stringers and a soft transom.... You can drill some holes with a 2" hole saw in the deck (only deep enough to go through deck) and take a piece of pipe and push it into the foam. Then take something to push the foam out of the pipe and squeeze it to see if it's wet....if you have wet foam you need to open up the deck and investigate further.

 

[edylina]

Re: 1975 75hp johnson stinger 2 hard to plane

I do suspect moisture in there there is a piece of plywood screwed to the floor in the back as a poorly done repair by the previous owner. I'm going to pull it up to check the foam and stringers later this week when I go back over to do some more work on it

 

[rickryder]

Re: 1975 75hp johnson stinger 2 hard to plane

When you do that check back in the hull rebuilding section for futher instruction