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Old 09-20-2018, 01:12 PM
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tatronation tatronation is offline
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91 prostar 351w Engine loss of rpm, power, and won't restart

Hey guys. last week i had to get a tow back to the landing. to start the day the boat ran great. started normal (carb boat) and was warmed up like usual. temp was good (150-160degrees) and oil pressure was 60psi also had plenty of oil on the stick. gas tank was 3/4 full of 91 octane no ethanol. I was pulling my buddy skiing and we were going 34mph. on the first ski set of the day the boat had a sudden loss of rpm and did not sound right. no knocking or ticking though. The perfect pass stargazer read 32 mph and i pulled the throttle back to idle and before the boat coasted to a stop the boat was off. i got it to fire over and run by pumping the throttle but it would quit a second after letting off the key. i tried one more time and things just didnt sound right and i got a backfire. towed back to the landing by a pontoon because i had heard enough to know i shouldn't keep pushing it.

I haven't gotten it to run since. Tried running it on the trailer and it doesn't have the normal sound to when it cranks over. it has almost a more airy sound to it, but very hard to describe.

things i have checked so far:
Replaced coil
grounds are good
voltages are correct at coil, battery, dash, etc.
has spark
has fuel
rotor is not way off... what i mean is at TDC on cylinder 1 the rotor points to cylinder 1 on cap.
weights and springs in the distributor are oiled and in good shape. they move freely.
with the valve covers off it seems as though everything is working as it should. no bent pushrods, dropped valves, etc.
has some sort of compression (haven't checked yet but ill get to why in a sec)

What i have found:
slack in the timing chain...
see the pic, but with the water pump off and turning the motor over with a wrench i found that when going clockwise with the crank and then turning the motor counter clockwise there is a lag to when the rotor starts to spin again. the picture below shows this. where my finger is is where i stopped turning the motor over going clockwise and there the indicator is showing is where the rotor started to move again going counterclockwise. I haven't checked compression yet because a stretched chain will mess up the valve timing and won't give me an accurate reading anyhow.

So, i guess my question is.. is this actually my issue? would a stretched timing chain cause a sudden rpm loss with no prior symptoms? what else should i check for while im troubleshooting and before i order a new chain and gears?


boat specs: 1991 prostar 190 with gt40p heads, mallory ylm ignition, edelbrock performer intake, holley 4160. 730 hours.

thanks in advance.
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  #2  
Old 09-20-2018, 01:33 PM
EricB EricB is offline
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An "airy" sound? That's a new one.... Can you describe it better? Do you mean it cranks over faster than normal? Remove the spark plugs and see if it cranks over any different. Compression test will be the tell-tale.
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Old 09-20-2018, 02:20 PM
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tatronation tatronation is offline
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Quote:
Originally Posted by EricB View Post
An "airy" sound? That's a new one.... Can you describe it better? Do you mean it cranks over faster than normal? Remove the spark plugs and see if it cranks over any different. Compression test will be the tell-tale.
ill try.... it was almost a "Pffft pfft pfft" sound rather than the normal crisp cranking noise. like valves opening a bit too early or late. had an almost deeper tone to it. with plugs in it cranks over the same speed as when it was running normal before. and it cranks over fine/ normal but fast without spark plugs in it.
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Old 09-20-2018, 11:24 PM
lakelizardofshred lakelizardofshred is offline
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Engine stall, no restart

Sort of in the same boat. With the above issues you checked already, I would guess to check the IAC, ICM next. Make sure itís not fuel system supply related (fuel regulator, supply pressure).
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Old 09-20-2018, 11:27 PM
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tatronation tatronation is offline
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Quote:
Originally Posted by lakelizardofshred View Post
Sort of in the same boat. With the above issues you checked already, I would guess to check the IAC, ICM next. Make sure itís not fuel system supply related (fuel regulator, supply pressure).
not sure what those acronyms are... i have a carburetor...
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Old 09-21-2018, 06:43 AM
88 PS190 88 PS190 is offline
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Starts when cranked. Dies when switch off.... check safety switch.
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Old 09-21-2018, 08:49 AM
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Quote:
Originally Posted by 88 PS190 View Post
Starts when cranked. Dies when switch off.... check safety switch.


Safety switch is bypassed....


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Old 09-21-2018, 09:08 AM
88 PS190 88 PS190 is offline
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If it will fire at all while cranking I don't think your timing is causing the issue.

Safety switch bypassed eliminates that so I'm going to bet on carb issue.

Get an empty soda bottle and drill a tiny hole in the cap, then put fuel in bottle and dribble some in the carb while someone tries to crank it. See if it hits. Sounds like when you "pump" the throttle you are squirting fuel out of the accelerator pump but that you don't have fuel otherwise.

Last edited by 88 PS190; 09-21-2018 at 09:36 AM.
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Old 09-21-2018, 09:52 AM
Cumminscj Cumminscj is offline
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If it runs when you pump the throttle then you likely have something blocking some jets in the carb. The carb is getting fuel and that is how the accelerator pump has fuel to add, but it sounds like something came loose or plugged a jet.

On these carb boats(and most efi boats) I will generally see if they will run off fuel or starting fluid like 88 stated above. That way you can eliminate all of the ignition and electronics very quickly and narrow it down to a fuel delivery issue. Or if it won't run off starting fluid then you know you have an ignition issue. One word of advise is keep a fire extinguisher handy no matter which type of fluid you use to try and start it.
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