787 ugly under head surprise 98 speedster

[hellz_wings]

In my 1998 speedster the boat engine was not starting right, randomly shutting off, didn’t run right, stall at low rpm, had a vibration/rattling noise coming from back ,etc. I decided to do a full tuneup to see whats up (carbs, new filters, oil, head gaskets, peek inside to check pistons, plugs, clean raves etc.) turns out that inside the head is not as pretty as i’d hoped:

1) cylinder and piston have visible rust (see pic): can i sand those off? Cylinder walls feel more or less smooth and the tops of the cylinder as well (aside from a few rust spots)
2) underneath the head has like chunks missing (see pic)(very pitted, prob from detonation / lean condition?) there’s also a ton of white powder and corrosion everywhere where the water passes. I was gonna dump head and valve cover in like spray9 and redo gaskets but is this head even worth salvaging? Or should i source a new good used one?
3) is spray9 the best thing to soak these parts in?

If i need a top end kit, can this be done in the boat and how do i know if it’s stock bore or been overbored ?

 

[hellz_wings]

Hey guys ,

just wondering if someone could please take a look at the vid here showing a few things i am unsure of:

1) loose piston - at TDC the pto piston seems loose-ish when i try to move it manually. The mag piston not so much.. don’t have too much experience with poston behaviour, so was wondering if this is normal or is something else wrong down lower? I would rather not have to remove exhaust, cylinders etc. If i dont have to and this is fine (not looking for perfect engine
2) cylinder corrosion - can i remove this with some thin brushes (obviously wont be able to totallly remove it all) and call it a day? Or do i have to remove the cylinders and get it fully cleaned?
3)carbon ring offset: not sure if its carbon ring or PTO that turns wobbly (offset) most likely is that bellow/carbon ring assembly is a bit offset but it’s hard to see in the vid.. it’s centered and then as the engine turns the driveshaft is offset in the carbon ring.. does this mean PTO or driveshaft is crooked and/or maybe bellow/carbon ring need to be replaced?

Vid below, thanks!!:

 

[hellz_wings]

Hey guys, was able to get the cylinder water jackets cleaned as best as i could and also light sanded and brake cleaned the piston crowns, this is what it looks like now:

 

[hellz_wings]

Also, what is this hose back here? It looks like one of those famous grey lines that causes problems. It’s coming from fuel tank. Should I replace it, and if so, with what?

 

[hellz_wings]

New pics of head and head cover cleaned: notice there is still pitting in the combustion chamber part of the head… will that cause any issues? Should i attempt at sanding to smooth it out?

 

[mikidymac]

Well, that engine had metal go through it.
It has 0.25mm oversized pistons so it has been rebuilt but not sure it the damage to the head was before or after the new top end. If it was after the crankshaft is shot, if before hopefully they put a new crank in it.

the rust in the cylinders is from moisture sitting in the engine and not fogging and/or winterizing it. It will lower compression and will eventually cause accelerated wear on the pistons but no good way to guess how long until it fails. A compression test will help shed some light on it.

If it was mine... split cases and inspect crank and bore cylinders to next oversize at minimum. For years of reliable service to come, replace the crankshaft when it is apart.

 

[hellz_wings]

Well, that engine had metal go through it.
It has 0.25mm oversized pistons so it has been rebuilt but not sure it the damage to the head was before or after the new top end. If it was after the crankshaft is shot, if before hopefully they put a new crank in it.

the rust in the cylinders is from moisture sitting in the engine and not fogging and/or winterizing it. It will lower compression and will eventually cause accelerated wear on the pistons but no good way to guess how long until it fails. A compression test will help shed some light on it.

If it was mine... split cases and inspect crank and bore cylinders to next oversize at minimum. For years of reliable service to come, replace the crankshaft when it is apart.

Yeah that’s what I thought :/ I am also hoping the metal was pre-rebuild. In any case, i will likely re-assemble as is and see how it runs, and do a compression test to see what’s up. One odd thing is that it looks like the pistons don’t match, one has a swirl pattern and the other doesn’t (the non swirly one is the 0.25 overbored piston, the other one says 81.89 on it.) Could it be they only replaced one piston? They slide up and down fairly smoothly in the cylinders with pretty much zero obstruction, this is all with the jetpump still connected. I guess if it runs badly i’ll rip it all apart again and remove cylinders, inspect crank/replace pistons with 0.50 and hone cylinders. What do i need to look for in the block with the crank? Metal shavings? Crank chunks missing?

 

[hellz_wings]

Btw any idea about that grey fuel line? I kinda wanna replace it outta principle, just not sure what to replace it with?

 

[mikidymac]

Standard automotive fuel hose is fine, not fuel injection hose. On the boats you might be better off buying marine rated hose, not sure if the Coast Guard would inspect you or not.

 

[hellz_wings]

Prob not as im on lakes only, however will have family on boat so want it to be 100% safe, especially when dealing with fuel. Is that thing back there a fuel selector? And what siZe hos is that? I may just remove it and bring to a parts store and find newer hose that matches

 

[hellz_wings]

called the seadoo dealer.. They had 5 feet left of this hose. Hopefully it's the good stuff . This is the line that goes from the fuel pump to the engine (not to the carburetor). I am curious though, why would a fuel line go to the engine? I thought all fuel went to the carbs?

 

[hellz_wings]

Also, what is this hose back here? It looks like one of those famous grey lines that causes problems. It’s coming from fuel tank. Should I replace it, and if so, with what?

Btw for the pic above, the hose that comes out of the fuel pump, the grey tempo line: I have new tempo line but I am wondering is this a pulse/vent hose? It goes to the back of the engine (mag side). If it does not deliver fuel, does this need to be changed? All other hoses have been changed to newer black hose style.

 

[mikidymac]

That is the pulse line to operate the fuel pump, no fuel is in it. It doesn't need to be replaced. The Tempo fuel tank vent lines don't need to be replaced either

 

[hellz_wings]

Thanks for the info! I won't go ahead and replace it then since it seems to be in good condition externally.

 

[hellz_wings]

This may be a stupid question.. But since the fuel pump is back there, does that means my carbs don't have a fuel pump on them? (ie: there are carb kits that are for non fuel pump carbs and fuel pump carbs). Just wondering which one the speedsters have. Thanks

 

[hellz_wings]

Update: took apart other engine and looks much cleaner, less corrosion, cylinder head has zero pitting (i actually bit the bullet and ordered a good used head for the other engine because it was so badly pitted). However, this one has me baffled.. there is some metal peice welded or stuck on to the top of the piston on the MAG side piston (see pics). Should i attemp to file/sand this down to be smooth with the piston? Is this some sort of repair or metal that somehow melted to the piston at some point in time? It’s about 1/16 of an inch in height so not super thick, but concerning nonetheless:

 

[hellz_wings]

Aaaand here’s the culprit… lol.. how does this even happen? The rave valve is broken and part of it melted on top of the piston.. im assuming other bit and peices got into the crank case? I’ll be tearing off the cylinder jugs for sure now and will do my best to get into the crank case to clean it all out. Also, do I need to replace the cylinder jugs? It looks like where the rave valve sits on the cylinder surface, it is indented slightly, meaning it will now always be to deep into the cylinder which may have been what caused the issue in the first place?

 

[hellz_wings]

Ended up taking off cylinder jugs, exhaust, carbs.. found that piston was scored on side and the ring seems stuck in the piston groove. Isn’t it supposed to move a but freely? In any case I’m sending cylinder jug thats good to get machined, im buying a used one to get machined as well (my other one is too messed up where the rave valve seats and on the inside there are metal burs so best to trash it imo). The rave valves will get matched and i’ll put in a set of wsm platinum pistons with new rings, pins, bearings, gaskets, etc.

 

[hellz_wings]

 

[hellz_wings]

While all that junk is off, now's a good time to replace those two tiny 1.8" oil lines that go from the pump on the MAG side to the rotary valve cover. It looks like they have a sort of unique fitting to them, so I'm unsure of what to replace them with.

Someone recommended TYGON fuel line that is clear so I can see if oil flows through them (that's genius). I found this product and wanted to confirm that I could just pull the old lines off and cut these to the right length and just slide em right back on (and put those small zip ties to secure em):

TYGON LP-1200 FUEL LINE TUBING | Aircraft Spruce Canada

 

[mikidymac]

I use high quality zipties with the stainless locking tab. Brand is Thomas & Betts I think.

 

[hellz_wings]

stainless locking tabs sound secure to me. There's a few sizes on amazon. Here's a pack of 1000 but they look a little too wide and long for those tine oil lines: Thomas & Betts TY25MX Cable Tie 50lb 7" Ultraviolet Resistant Black Nylon with Stainless Steel Locki : Amazon.ca: Tools & Home Improvement

 

[mikidymac]

You want the 4” ones.