86' 150hp Mercury XR2 Problems Previously 'boat speed question'

[wired247]

Re: 86' 150hp Mercury XR2 Problems Previously 'boat speed question'

I run a 21P Rapture on my 16' Avenger (600#) speedboat with a Merc 135HPV6. I can hit 60, and thru experimentation, it appears to be the best motor/prop ombo. A 23" pitch gives a bit lower top end and hole shot. I never thought it necessary to try a larger pitch. I am with sparkie on this one....

Depends on the hull and prop. I can run a 23 pitch 4 blade turning point to 66 MPH at 6200 but it has way too much bow lift and is flat dangerous to drive over 58 MPH. 17 foot checkmate enticer at 1500 lbs dry. With a 26 pitch Mercury chopper prop I have something like 15% slip and the bow is flat with the water but it powers through to 60 MPH. Terrible numbers but its steering smooth and straight and its safe to drive all day that way.

 

[Faztbullet]

Re: 86' 150hp Mercury XR2 Problems Previously 'boat speed question'

I run a 21P Rapture on my 16' Avenger (600#) speedboat with a Merc 135HPV6. I can hit 60, and thru experimentation, it appears to be the best motor/prop ombo

At what rpm as calculator at 10% slip puts it over 7000rpm!!!
Retest your compression hot and cold, if its below 100psi your wasting time and money. 90psi is about minimum a 2 liter will run halfway decent at.

 

[SparkieBoat]

Re: 86' 150hp Mercury XR2 Problems Previously 'boat speed question'

What year / model 17.5 lund? What hull design and weight?? fiberglass or aluminum?? all these make a huge difference in what prop will work. A 25 pitch prop will only work on a fast hull design like a bass boat and the motor would have to be in tip top shape. Those 2.0 motors lack some of the muscle for a hull that has a lot of drag/weight. I ended up putting my 2.0 back on the pro craft bass boat it came off of and getting me a 2.5 merc 150 for my Sea Pro SV 1900, BIG HUGE difference, I gained about 6 MPH and a way smoother low/mid range response. most bass boats I know of with that 2.0 motor are running 23 pitch props. some 21. most running well over 50 MPH. I again would say that with all the questions and confusion and numerous post on this boat, the poster would be best served to pay a pro for a check, I could probably trouble shoot that set up in less than an hour if it were here and have him going good in no time for not much money. that is unless he really does have a compression issue, which I could determine in about 10 mins with my trust worthy compression gauge.

 

[jordy1380]

Re: 86' 150hp Mercury XR2 Problems Previously 'boat speed question'

Its a '93 1750 pro angler deep v and I'm not sure on the weight of the rig. Its a 6 person capacity if that gives you any help. To go back on my 'problems' I was having, I did clean out the filter in the fuel pump and there was quite a bit of junk in there. Sediments and such that were black and brown colored so I'm guessing its chunks from fuel lines deteriorating.

 

[jordy1380]

Re: 86' 150hp Mercury XR2 Problems Previously 'boat speed question'

Ok, so I got my new compression tester in the mail today and I tested all of my cylinders at 118-120 so they are all good, you guys were correct in that I got a crappy tester. DO NOT BUY THE HARBOR FREIGHT TESTER!! lol that's the one I used and it is def a POS. So now that I cleaned my fuel filter off and compression and spark checks out, what is the next thing that I should look at before I make any attempts to clean my carbs?? I was thinking about doing some tests to be sure that fuel actually goes through the lines?? I haven't tried to start it again since I cleaned the gunk off of the fuel filter as I haven't had time to tinker with it besides the 30 mins of compression testing that I did today. I'm going to be sure that fuel goes through all the lines before I decide to mess with the carbs. Would it help to change the fuel lines and oil lines on the motor?

 

[jordy1380]

So, I'm going to bring this thread back to life....I know it's been a couple of years but I haven't solved my issue and I am a bit more experienced than I was previously. I've had the same issue with the motor over the past couple of years with it not working consistently. The idle rpms are good around 750 and if my memory serves right at WOT I can get it to around 5k and on a calm day the boat will go 45mph. Last time I checked, compression was good around 120psi and sparks were good on all 6 cylinders.

The problem with the boat is that it won't get on plane with the gas tank full or more than two people on board. I will put the handle to WOT and it won push past 2000 rpms and will just sit right around 8-10mph without ever getting on plane. Occasionally it will pop through and rpms will shoot way up(cavitation I'm assuming)and I'll have to back off on the throttle but it will then get on plane. Usually if there isn't a heavy load on the boat or the tank is half full it will work this way. I do have the repair manual and some time this summer so I was planning on working on it and learning more about troubleshooting. Anybody got any idea what to look for?

Also, the issue previously mention with problems starting the motor has been solved. There was a loose connection in the ignition switch which wasn't engaging the choke solenoid so there wasn't any fuel getting to the engine for it to start. So that problem has been solved. I'm going to put in a new water pump and T-stats in a week just for maintenance purposes since it hasnt been switched out for a few years and it seems to run pretty warm.

 

[Chris1956]

OK, what pitch prop are you running now?

 

[jordy1380]

Sorry it took me so long to get back to you. I didn't know the size off hand so I had to go look. It's a 23 pitch. The size and pitch is 14 1/4" x 23.

 

[Teamster]

Sounds like it's time to try a smaller prop,..

A 21p or maybe even a 19p,........

 

[Chris1956]

In theory a 21P prop will give you 5400RPM. A 19P prop will give 5800RPM. Of course, when you get into the powerband, the RPM may increase a bit more.

 

[CharlieB]

Couple things. Not all compression gauges are created equal. Different gauges will often give different readings. The number itself isn't near as critical as the range of numbers of the cyls. As long as they all are near the same is most important. If the motor has enough compression to start then it most likely will be fine for a fishing motr, it may not win any races, but it will get you there and back.

You never mention using the choke to start the motor. I need to be sure you know it is there and how to use it. With the key turned on just push the key forward, the center barrel of the switch should push in a bit. This is the choke and must be engaged and held while you turn the key to engage the starter. Once the motor fires you stop pushing it in same as you stop cranking the starter. HOWEVER you must still be ready to 'bump' it in just a touch and release again it the motor speed falters, as if it is going to die while cold. Once there is enough heat built into the cyls the idle speed remains steady you won't need to touch the choke again until the motor has mostly cooled before restarting again.

Throttle opening. With the motor OFF, shift into gear and open the throttle WOT. Go back to the motor and uncover it. Check the throttle linkage and MAKE SURE that the carbs are WOT. A poorly adjusted cable causing carbs not to open complete can cause a lot of unneeded hair-pulling trying to figure out problems.

Another word about the choke. It can be used a s tool to help determine a motor problem. If you are running the boat on the water at WOT and the RPM is not getting up there, 'bump' the choke to see how it changes RPM. If it picks up any then it is a sign the carbs are not delivering enough fuel. If it droops as it should from too much fuel then this may not be a carb problem. Simple easy test can give you a clue to what/where a problem lays.

Do NOT be so quick to brame the prop for poor performance. You have verified spark on all cyls. You also need to check ignition timing, clean the carbs, and make sure carb linkage is set correctly to ensure the motor is performing to spec. Only after this can we even think of checking into the prop.

 

[jordy1380]

Yes, I do use the choke top start the motor. Push in on the key and turn until it starts or pops off. I haven't tried pushing in the choke while driving but I have squeezed the fuel bulb to see if that gives me more rpms but it never did anything. Also, I have checked that all the valves are completely open at WOT which they are as well as compression and sparks on all cylinders. The compression for all was around 120 and all sparks were good. As far as checking timing, I'm unsure how to do that at this point and I may give a shot at cleaning the carbs.

Is there any good site or tutorial that goes through cleaning the carbs in general and do you need to do a link and sync of all the carbs every time you clean them?

 

[CharlieB]

Every time you disturb the carb linkage you will need to be sure they are sync'd again as they MUST fully close together. If you do not disturb the throttle cable or the throttle cam lever that contacts the carb linkage you will not have to readjust that portion. But do verify that when the control handle is moved to WOT that the carbs are opening fully.

120 psi compression is very good. The motor should be capable of making its rated power.

Ignition timing is checked and adjusted NOT running, but with the spark plugs removed and all plug wires grounded to give the spark a place to go. An inductive timing light clamped on #1 plug wire, the throttlel in the WOT position so the timing lever is fully advanced. Key turned on. Crank the motor and the flash should make the timing mark on the spinning flywheel appear to hold still.

I don't trust my memory for the spec, you will need to find the service manual. It should be near 18 to 20 degrees BTDC. Look it up to be certain as it does make a difference. Too far off can hurt the motor as well as suffer poor power output.

 

[jordy1380]

I may try to clean the carbs this summer but we'll see if I get to it. We just had our first baby so a newborn definitely takes a lot of your time. I found some good videos on cleaning the carbs and it seems all you need to do to clean them is to pop off the throttle attachments from the side, take them off, clean them, and put them back on in the order you took them off. Doesn't seem too difficult. Thanks for the info CharlieB!