89 Mercury 135 v6 load trouble

[bordercountry]

Motor seems to miss on takeoff when under load. Mainly when trying to pull a skier or when there is lot of weight in the boat. It takes off fine with just me onboard. When under load it seems to not be hitting on all cylinders then all of a sudden it will start sounding better and take off. I had it in to a boat shop twice and this is what they did. <br /> The 1st time in they checked spark and compression - good. No spark on #6 cyl. Checked ignition system and found weak spark on #2 and #4 cylinder and no spark on #6. Power Pack is bad. Checked trigger and stator- checked out good. Replaced power pack.<br />Still did the same thing so I took it in again and here is what they did.<br /> Checked ignition system #1 cylinder has no spark. Checked components and found faulty switchbox assembly (other one) Found bad oil cap sensor-replaced. They also put in a new water pump.<br /> I took it to the lake and it ran fine with just me in the boat. Next day I loaded up the family and with the extra weight in the boat, same problem on take off. Once it catches it seems to run fine but I’m not sure if it hitting on all of the cylinders. I also noticed with the extra weight in the boat I am only turning 4400 WOR.<br />Any Ideas what is happening? I am running a 21 pitch prop and am considering a smaller pitch. This may be a stupid question but could the larger prop be not allowing enough rpm's for proper acceleration?

 

[AndyL]

Re: 89 Mercury 135 v6 load trouble

Assuming all your other faults are fixed in my opinion you are hopelessly overpropped. You should be pulling 5200 / 5600 I think. I would imagine a 17 inch pitch would get you there and may cure your problem now. Best to borrow one and test it before you commit yourself. However you must ensure that your ignition system is fully Ok as if there is still a problem with that you will not cure it with a change of prop. If I overprop my engine it is as sluggish as anything but I could still get 4800 at WOT. It is a different beast when propped for 5300. Good luck and post your results.<br />Andy

 

[down_time_1]

Re: 89 Mercury 135 v6 load trouble

I had a 135 v6 on my searay and was turning 5500 rpm 50 and 50mph with 5 people. I was running a 3 bladed ss propand had tried a4 blade, but it would only turn 5000 rpm with 2 people. I feel you need to get your rpm up to 5200 to 5500.Keep an eye on your water pressure and trim your motor out to get your rpm up. Hope this helps, GOOD LUCK

 

[bordercountry]

Re: 89 Mercury 135 v6 load trouble

Thanks for the input. I borrowed a 19 pitch prop today and I couldn't believe the difference. Motor ran smooth with no vibration and the RPM's were in the 5200 5300 range when I opened it up with 3 of us in the boat. I couldn't play with the trim much to see if I could reach 50 because it was pretty rough on the lake today but I’m guessing the 19pitch is the right match. No more lugging. It felt like the motor came to life and jumped out of the hole. Now I’m wondering if the problem I had been experiencing like a miss was more of a lug. Anyone know if a motor not making enough RPM's on takeoff will make a miss or could it have been loading up and seemed like a miss. I didn't experience any of that today.