1987 XP150 backfire

[Daron Dyer]

I have been having trouble with my outboard. I overheated it last summer and it would't start. I checked for spark and had fire on both banks. It still just backfired. I replaced the flywheel key, both thermostats,(they were melted) A new impeller and it started right up. Took it to Cave run a couple weeks ago. Wouldn't start, Just backfired through the exhaust as before. I think one one or both of my power packs are fried. Going in and out maybe. I also can't get my linkage right. I think I may have tweaked the shift rod. I measured it and it is in spec. I can only get neutral and foeward or neutral and reverse. Not both.

 

[fireman57]

Re: 1987 XP150 backfire

if you were hot enough to melt tstats I would do a compression check. I'm betting that you have a bigger problem.

 

[boobie]

Re: 1987 XP150 backfire

Do the compression check and you may want to pull the heads.

 

[emdsapmgr]

Re: 1987 XP150 backfire

Check the flywheel key again. It may have sheared. Best to disconnected the shift cable from the engine when you make the shift adjustment on the engine. Once you get it to where it will shift manually, then reconnect the shift cable. You may need to turn the thumbwheel on the cable end to get it to match up with the stud on the spark advance lever.

 

[Daron Dyer]

Re: 1987 XP150 backfire

The tstats didn't melt, the nylon pieces that hold them in place got melted. Not completely, but enough to need replaced. My compression is right around 100 on each cylinder, give or take a couple pounds.
I took the pwer packs off last night and inspected them with a magnifying glass. They looked fine. I did notice that all my coil pack bolts required at least a half a turn. I checked connections and was looking for a short.
I put the muffs on and got it to start. It hasn't started since May.It took about tweny tries. It idled OK for about two minutes and died.
I kept a sharp eye on the temp with a infared Temp gun. All cylinders ran close to 180. Number three ran about 185.
I got it to start again after checking the plugs. Now, I can't keep it running without applying throttle.
It sounds good. Am I getting weak spark as it warms up? I think I am going to replace the packs and coils to be sure.

 

[Daron Dyer]

Re: 1987 XP150 backfire

I truly beleive my problem is ignition related.I bought this boat new and haven't had any problems until now.
I just purchased two new mallory power packs. I got them for $185. I think this is a good place to start.

 

[fireman57]

Re: 1987 XP150 backfire

Get a spark tester and check your spark. It should jump almost a half inch with a bright blue spark. yellow is too weak.

 

[Daron Dyer]

Re: 1987 XP150 backfire

I have already done that. It is blue. The intermittent starting or not tells me I'm dropping a bank.

 

[fireman57]

Re: 1987 XP150 backfire

you can test the cdi box with a dva meter. There are step by step instructions at their website. I can't remember the name of it offhand but if you do a search for cdi testing I'm sure it will pop right up. Hate to see you spend the big bucks for it if you don't need it. Could just be a coil that overheats and cuts out. have you inspected them for cracks and such. you can also take the cover off and put it on muffs and start it in the dark and look for spark arcing to ground from them.

 

[Daron Dyer]

Re: 1987 XP150 backfire

you can test the cdi box with a dva meter. There are step by step instructions at their website. I can't remember the name of it offhand but if you do a search for cdi testing I'm sure it will pop right up. Hate to see you spend the big bucks for it if you don't need it. Could just be a coil that overheats and cuts out. have you inspected them for cracks and such. you can also take the cover off and put it on muffs and start it in the dark and look for spark arcing to ground from them.

I will sleep better knowing I have new power packs, The coils are next. I am getting tired of being stranded or relying on my trolling motor to get me back to the dock. These packs are 24 years old and have served me well.

 

[emdsapmgr]

Re: 1987 XP150 backfire

If the engine runs 185 degrees normally, that is too hot. Normal idle head temps should be between 145 and 155 degrees. Lower when the engine/boat is on plane. You will get a hot horn when the cyl heads hit 212 degrees. The horn will silence when the cyl head temps get back down to 175. 175 is still too hot for long life on that powerhead.

 

[Daron Dyer]

Re: 1987 XP150 backfire

I am using the infared temp gun pointing right at the cylinders next to the plug. My Warning Horn doesn't work worth a **** and never has. I have purchased a new one, but was trying to make one good run before putting it up for the winter. I work 60 to 70 hours a week and am trying to find time to get my baby running again. If I am running 40 degrees too hot. What should I do next. The plugs have no water on them.

 

[emdsapmgr]

Re: 1987 XP150 backfire

To address the cooling problem: check for water flow through the block. When the engine runs, you should have a strong stream of water out the telltale in the engine lower cowling. That indicates that the impeller is working. Good sign. The engine can still overheat at idle if the thermostats are stuck shut. Water must circulate through that stat housing and down the midsection in order to cool the engine. You can pull off one of the thermostat covers and temprorarily start the engine. You should get water out of the stat housing. Replace that cover, then pull of the cover for the other head and start the engine again. You said you replaced the nylon relief valves in the thermostat housing. Did you also replace the thermostats?

 

[Daron Dyer]

Re: 1987 XP150 backfire

I might have not had the hose turned up enough, I was revving it pretty good, I was just glad to hear it run again. I completely replaced all thermostat parts and springs. I used sierra kits. I got the parts brak down from evinrude.
i am worried about the springs, they were longer than the originals, but had a smaller wire diameter, they were red.
Since I can't really open it up on the hose, maybe they are putting too much pressure on the diaphram to allow proper flow.
I need to get back in there and flush the block real good, there might be some grass in there from the overheat last year.
I am definitely putting the warning horn back in working order before I take it out again.
Thank You for your expertise and I will keep you posted.
There are not enough hours in a day.

 

[Daron Dyer]

Re: 1987 XP150 backfire

I might have not had the hose turned up enough, I was revving it pretty good, I was just glad to hear it run again. I completely replaced all thermostat parts and springs. I used sierra kits. I got the parts brak down from evinrude.
i am worried about the springs, they were longer than the originals, but had a smaller wire diameter, they were red.
Since I can't really open it up on the hose, maybe they are putting too much pressure on the diaphram to allow proper flow.
I need to get back in there and flush the block real good, there might be some grass in there from the overheat last year.
I am definitely putting the warning horn back in working order before I take it out again.
Thank You for your expertise and I will keep you posted.
There are not enough hours in a day.

Well, I am back in the same boat again, It just backfires and won't start after the new power packs. I think the flywheel has slipped again. That would explain my hot temps. When I replaced the key the first time, it didn't look sheared at all, but after lining the flywheel back up, It fired right up. I think I have a key that is too small.

 

[emdsapmgr]

Re: 1987 XP150 backfire

You really need a factory key. Also, the torque on that flywheel nut is critical. 140-145 lbs for a V6.

 

[Daron Dyer]

Re: 1987 XP150 backfire

I pulled the flywheel again and I could tell it had been moving. I replaced it with another factory key and tightened it down with the impact. It was still moving. I could tell the key was not engaging. I pulled the flywheel off again and tried to get the keyway out and I couldn't. I had boogered it up a little, so I put the flywheel back on and it held without spinning and the engine fired right up. I let it run about 5 minutes and the head temps are still at 180 at idle. I really think the sierra tstat kits I put in have too much pressure on the springs not letting enough water in to the block. They were longer than the originals. I am going to pop them back open and shorten them to the originals size. Then I went to shut her down and it wouldn't turn off. I had the key in my hand and the e-stop lanyard. It was still running. Now I'm guessing ignition switch. I am about done and am getting tempted to sell it.

 

[emdsapmgr]

Re: 1987 XP150 backfire

Since you are having so many flywheel key problems, I suggest you lap the flywheel and crankshaft. That's a procedure for cleaning the two mating surfaces with valve lapping compound. The procedure should be in the factory service manual. That cleaning and correct torque should eliminate the problem. If you think there may be debris inside the cooling passages of the block, why not pull off the head covers. (not the heads) Once exposed, you can see if the head water passages have any debris in them. If you find anything, (grass/sand) it's likely the same stuff is inside the block also.