'94 Nitro 170 DC won't get on plane

[t.hagen]

Hey guys, just bought my first bass boat and I'm having a problem with it getting on plane. It's a 1994 Nitro 170 DC Rick Clunn Edition with 115 hp Evinrude, I got a hell of a deal on it so I felt like it was time to pull the trigger. I've spent the last couple weeks intermittently working on it when I got the chance, before I put it on the water. The main thing we fixed was a bad neutral safety switch. Yesterday we decided it was time for her maiden voyage to see what we were working with, and she just did not want to get on plane. We had the throttle full bore and it just kept plowing through the water. We trimmed it up and down trying to find the sweet spot and it just was not interested in getting on plane. Eventually it did plane out, but not until it mulled through the water for a minute or two. I noticed that it would get up out of the water quicker if we'd put her in a turn, or if we started to catch a little chop in the water. Another unusual thing dealt with the yaw, it had a tendency to pull hard right, to the point that you had to fight the steering wheel, it would be exhausting if you had to drive it for any significant distance. However, I think there is a trim tab on the back we can adjust. We've had the ear muffs on it out of the water, and that engine will flat out run, great response, and sounds good. Had the carbs rebuilt and all new plugs. I've asked two of my buddies for suggestions, one thought maybe the prop was slipping, and the other thought maybe I have a prop that is just too much for the boat to handle? I think the latter sounds more logical, that could make sense why it struggled to push the boat on plane, and once it was on plane, a clockwise turning prop would push the boat to the right? I'm just wondering if you guys have any suggestions? My father and I are both at a loss, he's owned multiple boats in his day, but they were all inboard ski boats, never an outboard with a 2 stroke. Thanks in advance!

[bison2312]

What prop and pitch?

[moetorola]

I had a 93' 170dc with 115johnson same as evinrude.

I used 2 raker props, 18p when I had 2 people and 20p by myself.

If I had 2 people (both of us weight about 180lbs) and full live well, half tank of fuel it was a dog getting on plane with the 20p raker. maybe 10seconds, switch to 18p maybe 5seconds.

I also raised my motor on the transom 2 holes, it was all the way down seemed to help. both holeshot and top end. My best speed was 52mph gps.

I usually never filled the gas tank more than half full.



I didn't use one, but you may look at installing a whale tail to help get on pad.




How much do you guys weight?

What is your RPM when trying to get on plane?

And as already mentioned what prop and pitch?

[t.hagen]

I have a raker 13.5 x 20 prop on it. I don't remember off hand what type of RPM's we were working, and the motor already has a whale tail installed. Our weight together was probably in the ball park of 400lbs, and only had a quarter tank of gas on board. Raising the motor on the transom could be something to look at. I found a forum here with someone dealing with something similar to me, seems logical? Let me know what you guys think. https://www.bassresource.com/bass-fi...at-wont-plane/

[Fishysam]

also till your on plane there is only one trim setting. ALL THE WAY DOWN, negative trim to be exact, something to look for would be some trim extenders, if you have them on the boat take them off.

[moetorola]

One other thing I would do is a compression test, probably have to do a leak down also. As my engine showed good equal compression on all 4 cylinders, but something was wrong.

My 115 Johnson, (same block and everything as your Evinrude) Ate a ring on a piston 2 different times. It ran great but would only hit about 4700 mix RPM by myself and quarter tank of fuel with an 18p prop. Had the engine fixed and was a different boat. Basically the pistion ring pin either falls out and allows the ring end gap to rotate to one of the ports, effectively chewing it up lake a pair of scissors.
Get a bore camera and inspect the cylinders, look for notches at the exhaust and intake ports. This would indicate ring has gotten chewed. Leak down test will show this.

I hope this is not the problem, but its seems the ol' OMC crossflows where known for eating rings.

[t.hagen]

We had a compression test done and it all checked out. Talked to a mechanic on the phone and he thought it could maybe be a timing issue in the motor, plan on taking it to him this week. We put it on the water again this last weekend and I made a point to pay attention to the RPM's, it bogged down at 2500 until it would start to take off, then it would shoot up to 4000, before settling back down around 3000. It would get on plane when just I was driving it, but with two of us in the boat, one of us would have to sit up on the bow to speed the process up. I'll be sure to suggest that when I speak to him again. Really hoping to get it figured out soon!

[moetorola]

what was your MAX RPM at full throttle just you in the boat?

If I remember correctly the crossflows had max RPM of 5500. you want a prop that will get you close to that.

Is your engine all the way down on the transom?

If you drop to an 18pitch, and still cannot hit 5400~5500, I would look at engine.

[t.hagen]

Don't remember me solo, with the muffs on we got it up to 6000

[moetorola]

Don't remember me solo, with the muffs on we got it up to 6000

On muffs don't count. Must be under load.

FYI, do not rev engine like that on muffs without load, bad things can happen.

[t.hagen]

I did not know that, thanks for the heads up. Also, motor is on the top holes on the transom

[moetorola]

Measure your Prop shaft to Pad measurement.

[moetorola]

http://www.bbcboards.net/showthread.php?t=157208