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Twin Engine Questions!!

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DiveMode

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Hello all happy boaters!! :cheers:

Guys- I've got a 96 speedster twin 717 and I'm wondering if ya'll can help... my port side engine runs higher RPM's than the starboard side, at WOT the port engine runs about 800-900 RPM higher. Also, when I take off on the hole shot, the port side will run up to 7000 while the starboard only hits around 6000. You can hear the difference in the engines when take off, but once the boat planes out the engines sound "tuned"... however, the RPM's are different. If I adjust the throttles so the RPM's read the same, the engines lose their 'tuned' sound and the boat will turn to the left slightly. Also, the idle speed on the starboard side is about 200 RPM lower than port.

1st ? - What should the idle speeds be set for these engines?
2nd ? - What things should I look for to tune these engines together?
(same RPM's, same thrust power)
3rd ? - I've heard about cavitation... could one side be cavitating and if so,
how do I check that out?

Thanks for the help gentlemen... will be checking back soon to see what advice ya'll have!!
 
I'll throw something out there....1500rpm in water/3000 on hose
Make sure adjustment screws are the same, if you have to, bury the LSA/HSA, and turn LSA out to 1.25turns, give/take .25, leave HSA at "0", Check wear ring clearance w/ that of the impellor, no more than 1mm gap, and if cavitation, should have high revs becuause no load on impellor, finally, check throttle cable/linkage, make sure, they pull the same, and do compression check. 150psi is ideal.
 
Timmy- appreciate the tips, I'll get on that this week. Pulled the compression already, around 145-148 on all four. I'll pull the venturi on both engines and check the clearance. Thanks for the reply!!:hurray:
 
No problem,...but you can look down the steering nozzles at the prop, and with enuf light, or flashlight from underneath, can almost visually see if gap is to much. Beats tearing it down
Does it take on water?
 
I don't think it takes on much water... I only hear the bilge pump come on maybe once every 4 hours or so... I think thats mainly from when we get in & out. The dog brings in a bit as well when he shakes off... ;) When I remove the drain plug I only get a little dribble.. it doesn't make a stream or anything.. also, the engine compartment always seems pretty dry. I'll try the flashlight trick here this evening after it gets a little darker. See what kind of clearance I'm looking at. I'll post back to you again tomorrow. Thanks again for the help Tim!

-Greg
 
Rpm....

I think you should trust your ear more so than the gage.

It sounds like you know what a "tuned" set of engines is suppose to sound like. If you set them both to the same rpm on the gage and they no longer sound tuned and then, leaning left, something isn't right.

I think I'd use a stroboscope type tach and check the rpm verses relying on that gage.
 
Snipe- is it common for the rpm gages to be incorrect? I don't have a strobe so is this something I should take down to the mechanic? These 717's have twin carbs and I've found them a lot more difficult to work on than my jet ski... it's pretty easy to get around the engine on the jetski and it only has one carb so I was able to work on it without many problems. When I read the shop manual for the boat with its twin carbs... I got a little disoriented with the pto/mag carb adjustments, cable adjustements, etc... I may be a little out of my league. Also, I have the repair manual on CD and I'm not real fond of it.. for me it's always been easier to read a book. That way I could have it by the engines when I'm trying to work on them.

Tim- I checked the clearance last night as best I could and it seems ok.. here's another thing I forgot to add - I bought the boat up in Wichita, Kansas and the guy said the altitude it ran at was around 1400-1500 ft. Up here in New Mexico we're about 3800 ft and some of the other lakes are around 4200 ft. The plugs are a little oil fouled. Reading the manual, it said to be very cautios about adjusting the LSA set screw because it could damage the engine. I know I need to lean out the air/fuel mixture and can do that with the HSA set screw (it only goes 1/4 of a turn with the plastic stopper) Again, with my limited knowledge of twin carbs, do you think it best for me to just take it to the shop?

Thanks again for all the advice gentlemen, I really appreciate all your time & help.

-Greg
 
Nope....it looks intimidating Greg, but its not. Higher altitude=less air in motor, which =foul plugs/wet plug look.
But I think ur alright at that elevation. That plastic stopper, is HSA, keep that at "0", and the LSA, start with 1.25 turns out, then +/- .25, dont hink you'll go higher than 1.25.
Back to carbs, you can access the LSA, by hanging upside down in compartment, if you cant with HSA, take airbox off, remove the 6 allen bolts, then access both,
Doesn't sound ike it was done, but pull plug wires off, and remove the boots and cut the ends quarter inch, then reinstall boots.:cheers:
 
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