New to me Rude 140, sneezing, won't idle and low top speed

[ctravis595]

I rebuilt the boat

It wasn't holding water but it was in need of restoration. The stringers were rotten and the transom was half rotten. I restored the transom with 4 layers of ply instead of 2 this time and spent a lot of time getting to know mr fiberglass, he's messy but stiff and reliable. I put her back in the water and I found my problem

The entire time I've owned this engine I somehow confused the positive and negative battery terminals even though the ground terminal clearly connects to the engine block. I'm a dummy

I wired the battery up correctly but have read incorrectly installing a battery will blow my rectifier and cause my engine to run on 3/4 cylinders. Explaining 99% of my issues thus far

Will report back after new rectifier

Thanks for the advice everyone. I feel much more secure on the water with my slight overpower on an old boat. My double cheeseburger transom should help. If I'm not happy with the 115 I might still install the bubble back since my engine already has the 140 carbs but I feel 115 on a 15 foot boat is plenty of power. The bubble back might improve my gas mileage however? I noticed that when I replaced my cars 5.0 v8 with a 5.5 v8

 

[jimmbo]

The Bubble Back isn't a simple bolt-on install. Some machining of the block will be necessary. The exhaust tuner from a 140, the 1977 version is best, will also need to be installed. If your engine is a 88/90 hp, the block would need porting and different cylinder heads as well. Actually the heads on a 140 and crank rated 115s are different too. If you do have an 88/90 hp, the 140 carbs will make for a poorer running engine, caused not by being over rich but actually lean, as the carb is too big for the airflow requirements. The engine can never use the extra flow at the top end as the porting really chokes the engine above 5500

 

[flyingscott]

delete.

 

[ctravis595]

Still Only tops out at 25 mph...I'm suspecting a spun hub, my prop is too small or a bad power pack

All cylinders feel warm

I replaced the rectifier, all ignition coils test for continuity, id like to check for spark while the engine is running but reaching over the moving flywheel just seems very dangerous to me especially if I inadvertently get shocked

I'm going to sand a mark in my prop and the hub and see if they line up after running WOT, I'm also going to look into adding a Tachometer to my rig so I can figure out what is going on RPM wise

I tried putting my engine in gear and spinning the prop and it didn't spin but I'm not convinced it's not spinning under WOT. The boat starts moving fine it just never planes out

 

[ctravis595]

Also reassembled carbs and they look spotless

Edit: I guess the bubble back mod has been discussed as nauseum but the conclusion seems you CAN install the bubble back without the extensive modification to achieve a mild boost in HP, as opposed to the full 25 horsepower boost. this is what I meant. I'm pretty sure I have the 115 and once I figure out my issue I will be content with the power without adding a bubbleback


Is the gas tank lid supposed to have a breather? Or is the gas tank supposed to be airtight?

 

[emdsapmgr]

The fuel tank is sealed when by itself. As soon as you hook a fuel line up to it, the tank head automatically vents to the atmosphere. That's normal, except on the old two-line fuel tanks. Best to try to figure out if you are working on a 90, or 115 flatback model. The 115's have better porting than the 90. If you've actually got a 90, but have 140 carbs, the excess fuel/air from the 140 carbs just won't run right on a 90 unless you rejet them slightly. What are the part numbers of the the heads?

 

[ctravis595]

I had trouble finding any numbers on the heads, they seem to have been painted at least once. I'll take another look

 

[ctravis595]

i also didn't notice anything i could adjust on my carbs. the screws that people often report have become loose on their carbs were so tight i couldn't loosen them. i figured since they weren't loose they were fine. used compressed air and all passages seem fine. visual inspection of all hoses reveals most have been replaced or are in good condition.

spun hub, bad power pack, fuel pump or fuel filter? any other ideas?

 

[ctravis595]

Today I started the engine while putting my hand on each cylinder and neither top or bottom cylinder was getting warm on the starboard side. Considering they are both controlled by the power pack I was already questioning it seems like a replacement is the obvious choice

Battery is still at 12.48 so it seems the charging system/rectifier is functioning correctly

 

[ctravis595]

i never like reading threads with no ending so here's another update for anyone who might have similar issues

i read up on how to test the diodes in the rectifier with a digital multimeter. neither my original rectifier or the extra rectifier i got with the engine were reading correctly (presumably from the mismatched battery connection). ordered a new one from ebay. still doesn't test out correctly. but they issued me a refund so i'm not too upset

ordered a new one that comes soon. in the meantime i decided to test my timer base to see if it has shorted or failed but i get good readings. i see none of the characteristic melted "goop" under the flywheel from a fried stator so i'm hoping it's not that

don't know if i mentioned it but i switched my power packs and the problem DID NOT follow the power packs, which tells me my power packs probably work, or at least work somewhat

cleaned out carbs with no change in performance. also did some seafoam treatment and for a while it almost seemed the engine was firing on a third cylinder on and off! i guess that's some progress...

i shifted the gear linkage by hand to verify it was fully in forward/reverse also

i've also rebuilt all spark plug wires to ensure none had been pulled apart

quick update on everything i've learned on it so far. engine tops out at about 23-26 mph depending on weight/conditions
restored the vessel to check for water containment, all good
idles rough
only two cylinders get warm it seems
strong telltale
hard to get started without throttle
figured out i hooked up the battery backwards. i have NO IDEA how the engine ran 10+ times with a backwards battery but on first round of tests it seems i need to replace the rectifier. possibly a stator or timer base. small chance the prop hub might be spun but i don't think so

 

[ctravis595]

finally have a rectifier that tests good. installed it today and took sandpaper to the ground points for the rectifier/power packs

still no spark on two cylinders

i guess now that i've tested power packs by switching them, tested the timer base and rectifier. all that is left is to swap around some ignition coils or i think i have a bad stator. i remember reading about how to test the stator but i still need to refresh myself. if i can't find a bad reading on the stator i will buy the DVC probes for working on boat engines and retest everything

luckily i have two "parts" ignition coils i can swap in to see if there's any change or maybe they just simply work better

i'm finding it a little weird that i bought the engine and it came with a "spare" rectifier (failed diodes) and also some spare ignition coils. seems like the previous owner was just recently debugging a similar issue. makes me think the stator might be bad and that's why he sold the engine. i wouldn't lie about it being a 140 if i was trying to sell a bad stator but who knows

compression checks good. if anyone has any ideas let me know

 

[ctravis595]

also my engine revs up during sharp turns. at first i thought this might be the extra cylinders firing but the boat doesn't go any faster so i've realized my engine is sitting a little high for how sharp i was turning, creating an "air pocket"(cavitation?not sure what it's called) around the prop

 

[ctravis595]

just wanted to follow up. since my last post i've rented another house, bought another and was working on a jetski engine rebuild so the boat was the last of my priorities.

finally got a flywheel puller, getting a socket to remove the flywheel nut and I think i will be on track to replacing the stator and getting this boat running good again

 

[oldboat1]

Busy three years. Can save some grief by using an air gun to remove the flywheel nut. Use a torque wrench when replacing it.