ok now what??? :(

[GuyWithTheCoolBoat]

ok things were going great. i was doing my fastest times (although still not quite where i should be. 57.2.. also being a marathon csr) and then... something happened. i had made some carb adjustments and things were doing fine. just the main needle. i had worked out to 40-41 clicks (from the 38 i had originally been running) to help with some slight "bogging".. i was running great and starting to figure out where the power was and then noticed after i turned around once and went to get on the throttle that i started really slowing down (nothing was changed from doing well to doing terrible because ti happened in the water.). my gps clocked me at about 45mph top speed achieved!!! i tore the entire fuel supply apart thinking something there. clean and no vac locks. i checked the bottom of the banjo nut to see if there was anything in the float on the carb.. spotless. i reset back to 38 clicks, refueled and my gps said 47.4 ( im attributing this to the calming of the water... it was fairly rough today)... im at a loss..i checked the mag.. hadnt moved still int eh same place. i checked the plugs as well. neither looked fouled and both looked good (and are brand new with about 5 hours on them).. .. other than the clicks out (that were reset to 38) i have changed nothing at all. i came back and refueled with the same fuel i had been using all along (93oct mixed 24:1 with valvoline 2 stroke mix... the same that ive been using since i got the boat.. even from the same station)... thanks for any pointers and sorry to bug you guys.... AGAIN.. but im getting stretched thin my whole racing fantasy...

[Jack Stotts]

Did the engine seem to be pumping water at the time it slowed? Could have gotten hot! I'd take the head off and see if there is any heat indications or scored cylinder walls. When reinstalling be sure to torque it properly. Jack

[GuyWithTheCoolBoat]

was pumping water as far as i know, but wasnt looking back to check. i know in my warm up tests afterward it was pumping water just as well as it has been. will tear off the head and take a look tomorrow

[bill van steenwyk]

different system/ have to check a different way

As you know the motor has no pump except for the prop throwing water. If you run it too high for too long, even though it still gets some water, it will start to overheat and then the problem compounds itself and eventually you end up with it hot and turning what little water you are getting to steam because you are too high, and causing exactly what you are experiencing. NOT saying it is, but sure could be based on the water system.

Best way to check to see you are always getting water is LOOK every lap at least once or twice, more times the more laps you run. If you can't or wont do that, run a hose from the discharge on the motor up the cockpit side by the throttle and you can see if it is pumping all the time.

ADD:
Just so there is no misunderstanding what I mean by "running the motor too high" I mean jacked up too high on the transom so when at speed there is a possibility of the cavitation plate being too high above the surface of the water so the "snout" is not getting a strong supply of water off the prop and then being forced up the tower housing to the power head.

[B Walker]

10 MPH is more than a "bit off"

If you over temped it, you can tell from taking the port cover off instead of the head and it is alot easier plus you dont waste a one time use gasket. Just hand turn the flywheel to visually inspect the pistons for scuffing paying close attention to the top piston. Should be super clean and no stripes down the side of the piston. If you lost 10MPH you either stuck it and you would know it or.......

Did the timing "walk" on you?

If the handle points all the way to the left facing the front of the engine, thats bad. Very common on new motors to have this happen cuz the 10MM nuts that hold the "horseshoes" or mag lock plates are rarely tight on new motors. The handle should point about 20 degrees to the right of the carb when facing the motor.

Assuming the motor did not overheat and the timing did not move, your down to fuel/carb. Given the superb history of Yamato electronic ignition systems.

But I am betting on one of the first two solutions

BW

[JBM]

What motor is it? If it's a 102, you may have problems with the points. I would check your timing either way.

[Al Peffley]

Suggestion

You might try a tried and true Wartinger cooling test setup trick for Yamatos:

Install a double male brass connector fitting with a clamp or ziptie onto the end of your upper or lower water outlet tube on a Y102 or Y302 powerhead side manifold (these tubes should be mounted pointing back and slightly upwards on your gas tank bracket.) Install a long piece of clear flexible tubing to the fitting using duct tape to temporarily attach it along the deck next to the combing wall up to a location next to your throttle hand (pointing out, not against your hand). Watch the end of the clear tubing the next time you test. Try different props and motor height/kickout setups and watch the tube for steam. Take notes on each setup, especially which props don't pump water and/or produce steam at top end rpm's. Shut the motor down at first signs of excessive steam. Works every time. Hope this advice helps you.

Al

[GuyWithTheCoolBoat]

transom height and set up are the same that it has been since ive have gotten the boat from sorensen 2 years ago, no changes. ill tear off the manifold instead of the head (although i do have a spare head gasket). could maybe a bad head gasket cause a compression loss and maybe a bit of a leak? how about a bad manifold gasket allowing some water in there to turn to steam and lean the pistons out mixing a bit of water in? im running 24:1 oil (valvoline 2 stroke mix) and tom johnston was saying that he runs 12:1 and some people have cut it to 16:1, yet the yamato site says 32:1... could i have been too lean and fried it?

[GuyWithTheCoolBoat]

10 MPH is more than a "bit off"

If you over temped it, you can tell from taking the port cover off instead of the head and it is alot easier plus you dont waste a one time use gasket. Just hand turn the flywheel to visually inspect the pistons for scuffing paying close attention to the top piston. Should be super clean and no stripes down the side of the piston. If you lost 10MPH you either stuck it and you would know it or.......

Did the timing "walk" on you?

If the handle points all the way to the left facing the front of the engine, thats bad. Very common on new motors to have this happen cuz the 10MM nuts that hold the "horseshoes" or mag lock plates are rarely tight on new motors. The handle should point about 20 degrees to the right of the carb when facing the motor.

Assuming the motor did not overheat and the timing did not move, your down to fuel/carb. Given the superb history of Yamato electronic ignition systems.

But I am betting on one of the first two solutions

BW

and the 10mph wasnt the bit off part. that was the 57 mph i was running a bit slower than the typical 60ish for the long haul sorensen runabouts. the motor isnt new and i did check the mag.. hasnt moved any. will also run tube to cockpit. its starting to sound like an overheating problem and maybe i fried it. im off to work now and first thing after work ill tear into it and see what i find... does anything in the timing ever go bad? (motor is a 302 that came from darrel sorensen running strong). also just changed to a new dewald prop. could this maybe be an issue with not throwing enough water? i ran a few hours between a couple days on it before the problem though.....

[Big Don]

IF you check all that stuff and it looks good. I would pull the power head and ck the pipe in the tower to make sure it didn't crack or break. I can't remember how much we lost in speed when our 102 pipe broke but 10 sounds about right. Then again i know nothing about 302's...

[B Walker]

If you had dropped a cylinder due to an ignition failure like a powerpack failure you would not have even gotten the runabout on plane.

One cylinder Yamatos are really doggy

BW

[mercguy]

10 MPH is more than a "bit off"

If you over temped it, you can tell from taking the port cover off instead of the head and it is alot easier plus you dont waste a one time use gasket. Just hand turn the flywheel to visually inspect the pistons for scuffing paying close attention to the top piston. Should be super clean and no stripes down the side of the piston. If you lost 10MPH you either stuck it and you would know it or.......

Did the timing "walk" on you?

If the handle points all the way to the left facing the front of the engine, thats bad. Very common on new motors to have this happen cuz the 10MM nuts that hold the "horseshoes" or mag lock plates are rarely tight on new motors. The handle should point about 20 degrees to the right of the carb when facing the motor.

Assuming the motor did not overheat and the timing did not move, your down to fuel/carb. Given the superb history of Yamato electronic ignition systems.

But I am betting on one of the first two solutions

BW

"one time gasket"??? The head gasket is reusable, as long as it is not "blown". It is not like the typical head gasket with a center crush ring............

[bill boyes]

To check for a broken tuner pipe just shake the motor while on the boat transom. IF you hear a clink pull the power head.
37 clicks is a bit lean. However, many needles do not run the same. Most most run around 42-44 clicks

[pro350hydro]

37 clicks is a bit lean. However, many needles run do not run the same. Most most run around 42-44 clicks

According to Ric Montoya, not all needles are manufactured with the same amount of clicks around it. Meaning, one motor will run great at 42 clicks, while another runs great and 30 clicks. Clicks are great for knowing where your motor is at, but hard to compare with another that way due to the difference in the needles

[GuyWithTheCoolBoat]

thanks for the info on the clicks. i was just going off what darrel sorensen said the motor was running at when he had it, and went from there. im on lunch and going up to shake the motor around and do the manifold plate, is there anything else i should check tonight when im not so crunched for time?