150 hp Mercury XR2 hesitates at WOT

jordy1380

Petty Officer 3rd Class
Joined
Apr 14, 2013
Messages
81
Ok, so I just got a boat with this motor in March this year and I've had some simple problems with the motor that I had to fix. I recently took it out on a trip with on of my friends and had some problems with it again! I've previously run compression and spark tests and I get compression around 120# on all cylinders and I get spark on all cyls. When I was running it this last weekend it started up great (previously it wouldn't start well but I found it to be that the business that serviced it before I got it had disconnected the enricher - easy fix) and it idled fine around 750 RPM (factory recommendation RPM). When I got it out of the 5mph no wake zone open the throttle about half way and I get up around 2000RPM then open more to WOT and it doesn't throttle up but it gets louder like it's trying to throttle up. Keep the throttle up and after about 8-10 minutes of going 2000 rpm it sounds like it passes something or moved something and revs up to full throttle immediately. I throttle down a bit to gradually get up to speed and it works fine until I throttle down to that 2000 rpm range. Every time I get around there, approx half throttle on the lever, it hesitates and stays around 2000 rpm until it passes the motor baby then just jumps up to full throttle so I trim back down a bit and throttle down a bit to get up to speed. I am going to check my fuel system again and change the bulb because it sounds like there's a blockage somewhere or it's sucking air until something seals maybe? I'm thinking my bulb is fine, but I'm just going to change the bulb because it looks older and probably hasn't been changed for a few years. Yesterday when I took it out the bulb filled with fuel fine, but Saturday when I took it out there were a couple times where it just felt like their was air in the bulb and wouldn't suck any fuel but the motor started up fine.

What are some things I should check? I haven't checked the fuel pump again yet, but about a month ago I cleaned the fuel filter and checked the diaphragm, which was fine. Could there be a problem with the diaphragm being too stiff? I thought about changing the gaskets and diaphragm in the fuel pump to see if that helps.
 

jordy1380

Petty Officer 3rd Class
Joined
Apr 14, 2013
Messages
81
Re: 150 hp Mercury XR2 hesitates at WOT

I forgot to add that I can easily throttle up above 2k when in neutral. It's just when it's under a load that it doesn't go above 2k rpm.
 

Chris1956

Supreme Mariner
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Mar 25, 2004
Messages
27,030
Re: 150 hp Mercury XR2 hesitates at WOT

That is a strange issue. Throttling up in neutral is not a test of anything, but it can blow the motor.

Pumping the primer bulb is a good way to test for a failing fuel pump. See if that fixes it. If not, and I don't think it will, maybe some of your electrical connections are dirty? Not really sure what to recommend.
 

jordy1380

Petty Officer 3rd Class
Joined
Apr 14, 2013
Messages
81
Re: 150 hp Mercury XR2 hesitates at WOT

That is a strange issue. Throttling up in neutral is not a test of anything, but it can blow the motor.

Pumping the primer bulb is a good way to test for a failing fuel pump. See if that fixes it. If not, and I don't think it will, maybe some of your electrical connections are dirty? Not really sure what to recommend.

Ok, I wasn't sure if that would explain anything with the timing or high speed wiring or jets if it throttles up fine in neutral. I've tried pumping the primer bulb when it's stalling and it doesn't throttle up any so does that indicate that it's not a fuel problem? If my jets are clogged in my carbs it wouldn't make a difference would it?
 

jordy1380

Petty Officer 3rd Class
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Apr 14, 2013
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Re: 150 hp Mercury XR2 hesitates at WOT

Duplicate post deleted...
 
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jordy1380

Petty Officer 3rd Class
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Apr 14, 2013
Messages
81
Re: 150 hp Mercury XR2 hesitates at WOT

Ok, so I took my boat out again Friday. I changed some zip ties that were on the fuel lines for fuel line clamps. I put another clamp on each terminal end and one by the primer bulb hoping that would fix the problem, which it made a slight difference. I have a new primer bulb assembly coming in tomorrow so we'll see if that's the problem when I switch them out. I think that the bulb doesn't have a tight enough connection.

When I took it out I got to open water then increased throttle to about half way then increased to full throttle and it hesitated again, but for less time than before. It stuck around 2000 rpm for about a minute before jumping up in rpms to get on plane. It seemed like I had to keep it around 3k rpms or it would bog down again to around 2000 rpm. It was either 20mph or 10mph lol. Once I broke the 2000 rpm barrier that it had it would take off fine. I didn't go full throttle because of the wind but got up around 4k rpm pushing me at ~30mph. I'm hoping to get it out again within the next couple of weeks after I switch the primer bulb and line to see if that makes a difference.

Does this sound like it's a fuel problem? Or could it be electrical?? (Hoping its not the latter!) I did try to prime the bulb when it started to hesitate and it didn't make a difference at all, just felt like it was pumping fuel up the line. It didn't make the engine hesitate further or give it a jump in rpms. I just had to keep the throttle up until it revved up past 2000rpms then I had to back it down a bit so it didn't try to keep jumping up more. I dont think an instantaneous jump in rpms is probably good for the motor.
 

quicktach

Petty Officer 1st Class
Joined
Aug 24, 2012
Messages
394
Re: 150 hp Mercury XR2 hesitates at WOT

Sounds like it could be a fuel issue. BUT it could also be an advancing issue (electrical). Fuel filters clean ? Any water filter ... clean ...any water ? Carbs ever cleaned ?
 

djcole89

Recruit
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Jul 18, 2013
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1
Re: 150 hp Mercury XR2 hesitates at WOT

Have you figured out your issue yet I am having the same problem.
 

jordy1380

Petty Officer 3rd Class
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Apr 14, 2013
Messages
81
Re: 150 hp Mercury XR2 hesitates at WOT

Sorry, forgot to reply to this!!

One thing that I did to see if it would help is change to new bulb, primer, and terminal connections on the primer bulb fuel lines. It did seem to make a tighter connection to the motor with the new connection. I've taken it out a few times since then and it did help some. It doesn't hesitate as much, or much at all, but it just takes a while to get up in RPM's. I have no problem getting 8-10 mph then it slowly goes from 11-15 mph then I almost have to advance the throttle all the way to get it to go any faster and it will still just jump up in RPMs. I think that I'm going to keep using it this way for the rest of the year because I won't be going out much more after this week. I'm going to save some money and either watch someone clean the carbs so I know how to do it or just pay someone. Then I'll see if this solves the problem. How much generally would it cost to have someone clean three carbs on a V-6? I don't have an inline filter before the filter on the pump, but I have cleaned the filter on the pump already so know thats not the issue. I've also checked the diaphragm and there's nothing wrong with that.
 

jordy1380

Petty Officer 3rd Class
Joined
Apr 14, 2013
Messages
81
So I've continue to have this problem this year with my boat. I replace the fuel bulb last year and it didn't seem to really fix the problem. Is the. Fuel bulb supposed to stay hard while under way? With it not bring connected to the motor the fuel bulb will harden but it just feels somewhat spongy when I connect it to the motor. I ordered a new one again but a better one. I know it's not the fuel pump as when I throttle up and squeeze the bulb it doesn't shoot up in rpms. I think my next step is to check the carbs. I don't think they need a rebuild but it's doesn't look too difficult to take apart and check the float and needle. Has anyone had a similar problem to this? Seems like I can work it to get on plane with one or two people in ideal conditions but with more people or wind it just revs up and remains around 1800-2000 rpms. Could there be a throttle/timing adjustment that I need to make? I have the service manual so I can walk through the steps if need be. I might take apart the carbs this winter just to clean them. The manual states that you don't need to take them apart completely to clean them just separate the fuel bowl from the main chassis and take out the idle jet screws along with the high speed jet screws. Do you suggest rebuilding or just taking apart to the manual specifications and cleaning with solution?
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
You might check to make sure the trigger is moving with the throttle and not sticking. Your original problem sounded like the timing was not advancing.
 
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