'90 XP100. Looking for advise on what to do next

[Phishnvdub]

Here's the background. This motor came on a 17' Starcraft Medalist 1700 fiberglass open bow I purchased a few months ago. Idled good on muffed so I thought everything was good. Had to a Marina for a water pump and to be looked over. Did pump and idled on muffs, said all was good and sent me on my way. Ever since then I have been battling with this motor to run right.

At first it would die at idle. VRO was leaking at the seams so I deleted it, blocked off pulse port and installed a fuel pump in the stock spot where it mounts against the crankcase. Seemed to help idle. Tried to test run in the river and would die in gear. Finally got it to go and ran like crap through the whole RPM range until WOT. Turns out the head gasket was blown between the rings that seal the cylinders and started letting water in lower starboard side.

To make a long story short. I replaced both head gaskets as the diverters in the one side were swollen so I wanted to do the other side to be sure. After a lot of research on here I have figured out the previous owner over heated it at some point. A couple spots had bubbled paint and some wire casings were melted. Things I didn't know to look for when purchasing. Also replaced cam roller and follower one on side of carbon and the other that rides in the groove in I think the throttle arm as the outer plastic sleeves were missing.

Here is where the motor stands as of today. It idles better on muffs. Is a little rough but does not die. Actually a little higher than before. Compression is low about 100# in top two cylinders and 90#,95# in bottom two. With this in mind I took it out for a water run today. Died when put into gear again. Somehow I got the fast idle lever down and got it to go. Once over idle in gear it ran like a beast through the whole RPM range. Up on plane in literally seconds. GPS said top speed was 42MPH. I would have thought with compression being low it would not have the power it did. From almost a trolling speed to WOT there was no hesitation and it ran really smooth. I probabbly ran it for a little over an hour at all different throttle positions and it ran awesome. Just made sure not to bring it to neutral until I was back to the boarlt launch.

Now, I noticed the bottom of the carbs are wet. The lower one more than the top. Looks like fuel bowl gaskets are leaking. Also here is a picture of the plug after some idling on the muffs and the running I did today. I put new in when I did the head gaskets. I am thinking about getting a good service manual, rebuilding carbs and doing anlink and sync then seeing if it will idle better and go into gear with out dying. I definitely think the sync is off a bit. Would I benefit from doing these things, or do the compression numbers make it not worth it? If I can get most of the summer out of this motor I would be happy. Then try to rebuild it over the winter. I have my second daughter due in a little over a month so thats going to kill having time to overhaul any time soon. Really want to get my 4 1/2 year old out on the water. Lol she has been asking for weeks and waiting very patiently to go out on the new boat. After running it today I am hoping there is a chance with out a major overhaul yet. I am sure some of u guys know how it is, trying to do things with the little ones that I never had a chance to do myself.

 

[multimech]

Re: '90 XP100. Looking for advise on what to do next

"Ever since then I have been battling with this motor to run right." Take it back to the shop. They have a responsibility to ensure their work is done correctly and fixes the problem they "resolved". If they tell you to screw off, then pull the carbs and rebuild them. Check your fuel lines, lift pump and hoses to the engine from the boat tank.

I hope you meant "I deleted the VRO and added oil to fuel when I did."

 

[multimech]

Re: '90 XP100. Looking for advise on what to do next

BTW that plug looks normal to me.

 

[emdsapmgr]

Re: '90 XP100. Looking for advise on what to do next

Your compression is off a little. Usually it should be within 10% on all 4 cyls. Your 90 is a little low. If there was a ring problem, you'd probably have noticed pits in the piston crown or the heads when you replaced both head gaskets. Since you made no mention of that issue, the powerhead could benefit from a can of engine tuner: The compression may come up a little with an application of Bombardier's Engine Tuner. Your idle/running issues are probably carb related. Poor idle may be from restricted idle passages. They are not very large and tend to clog with dried fuel gel over time. When that happens it just won't idle down. Conversely, once you crack the throttle and other jets begin to feed fuel, the engine seems to run ok all the way up to WOT. Typical of carbs needing an overhaul. I think it's worth a little of your time and $ the way it is.

 

[Phishnvdub]

Re: '90 XP100. Looking for advise on what to do next

Thanks guys. As far as going back to the marina, I think I am just going to leave that alone. Just don't want the hassle. I definitely did add oil when I deleted the VRO. I wasn't sure how much gas was in the tank so I filled it. Them added the proper amount for 19 gallons.

The tops pf the pistons and inside the heads looked great. I think inside one of the heads there was like four small pin tip size knicks. Almost not noticeable. Those were on one of the higher compression cylinders. I would think a sucked ring would cause a lot more havoc, but I could be wrong. Would seafoam work like the engine tuner? I am going to order the carb kits tonight along with a factory service manual. I found one on eBay for my exact motor but is was for a '91. I have to research of the '90 and '91 are the same. I thought I had read they changed in '92.

 

[emdsapmgr]

Re: '90 XP100. Looking for advise on what to do next

The factory carb kits are 439076. You will need one for each carb. Pits on the head or piston crown commonly come from a broken top ring. Usually also, that piston winds up with lower compression-not the higher compression you noted. Seafoam does claim to eradicate carbon deposits. A second application won't hurt anything either.

 

[Phishnvdub]

Re: '90 XP100. Looking for advise on what to do next

Ordered carb kits and a factory service manual yesterday. Will update when I get them installed. Should I go ahead and do a link and sync too, or wait to see what the new carb kits do first?

 

[emdsapmgr]

Re: '90 XP100. Looking for advise on what to do next

Once you get the factory manual, you can see how to do the sync and link. Familiarize yourself with it, by checking to see how close your current setup is. You may find out it is ok, or may need slight adjustment. Anyway, it will be a beneficial learning experience.

 

[Phishnvdub]

Re: '90 XP100. Looking for advise on what to do next

Got my manual earlier this week. Hopefully weather will cooperate tomorrow afternoon so I can rebuild my carbs. I have a question about my manual if anyone happens to see this post tonight. I paid $60 for a factory service manual for my outboard and got a photo copied version with a plastic ring binding. Won't say name of web site but no where in description does it say I was getting a copy for $60I thought I was getting an original. Is this how a lot of these come? Or should I say something to them. The black and white diagrams look OK but some of the pics being copied look a little over exposed now. Example would be like a picture of a pair of pliers and you can see the jaws of them but handles blend into the back ground and you can't see them. Am I being ridiculous?

 

[emdsapmgr]

Re: '90 XP100. Looking for advise on what to do next

I've gotten photo copies of original manuals from the OMC/Bombardier OEM supplier of manuals. I even called them about it. It's hard to trace a wiring diagram which is in black and white. Guess that's the way it is. The ones I've gotten are bound properly (cheap covers) and the reproductions were all fine, with the exception of the color foldouts..... Maybe a good time to shop for a used original on ebay.

 

[Phishnvdub]

Re: '90 XP100. Looking for advise on what to do next

I finished up rebuilding the carbs yesterday. Over all they were pretty clean inside. The biggest problem were the plastic float bowls were leaking bad. Turns out they were warped. New metal ones are about $130 a piece and you have to replace four of the jets. I had read a thread on here about sanding the sealing surface down so it would be flat and seal properly. I took a scrap piece of granite counter top, laid down a piece of 600 grit wet/dry sandpaper and let the garden hose trickle over it and sanded them flat. Worked great. Starts up and idles much better now. Still wants to stall when I put it into gear on the water, but it's easier to get the idle lever down and take off quickly now. Before you would get lucky to get it to go with out stalling. I still have to decarb and thinking about doing the link and sync. Not having the piston stopper and never using a timing light have me a little scared I may screw it up and have it not run at all.