Full Bore Tech Tips

Always refer to the proper service manual when removing and reinstalling an engine or for most service work.

This page is only to help with the most commonly overlooked or missed issues. Don't forget to see what all we have to offer you here on our website for your Sea Doo needs.

After boring the cylinders on a Sea Doo 787/800 947/951 or any other engine with a power valve, you must relieve the exhaust power (RAVE) valve for clearance or you will snag your rings and destroy your new top end. The old rule of standard bore and first over don't need the valves relieved doesn't always hold true. As things wear they tend to get closer and eventually they make contact even on std bore with high hours.

This edge can be relieved with a hand file or dremel tool (die grinder with sand paper drum)

You are only removing enough for clearance between the valve and the piston rings.

Never reuse the old spark plugs from a failed engine in your fresh rebuild. Small pieces of contaminates may be lodged in the plug and drop out after they heat up.

When disassembling the top end of Sea Doo (2 cycle) engine watch for the notorious cageless upper rod bearings the needles will fall out everywhere.

Take precautions and cover the crankcase when removing the pistons. Full Bore top end rebuild kits come with caged needle bearings.

When removing the flywheel be sure that you don't thread the puller bolts in too far, you can damage the ignition coils. The holes for the puller go all the way through the flywheel and the stator coils are right behind them.

If you have your engine (Sea Doo 580,650 or 720) rebuilt by Full Bore you can simply align the line (nick) in the stator plate to the engine block. This mark was made with your ignition, flywheel, crank, and engine cases at the factory when the engine timing was set.

This is another good reason to have Full Bore rebuild your seadoo engine instead of buying a remanufactured engine. We rebuild your crankshaft so the timing index stays the same.

The most common engine (besides water) failure on the mid 90's Sea Doo 580,650, and 720 is the small oil lines from the oil pump to the engine (rotory valve cover) break. From the factory they were painted. Over time they dry out and become brittle, then break. Often times the oil pump is blamed: do yourself a favor and check the lines.

On a Sea Doo this little rubber bumper goes on the end of the drive shaft, one on each end. Often you will find it stuck in the P.T.O. balancer after you remove the engine. If you forget, it the drive shaft makes more noise (rattle) than normal.

Don't use RTV silicone on any gaskets other than exhaust. On exhaust use hi temp orange. RTV will break down and dissolve when in contact with gasoline. Read the tube!!! Better yet, read the service manual and use the proper sealants.

When rebuilding the top end of a Sea-D00 580,650,720 or 800 the cylinders need to be aligned properly. After sliding the cylinders into place install the cylinder bolts finger tight. Bolt on the exhaust manifold this will properly align the cylinders then torque the cylinders. Note be sure to put loc tite to the threads of the inner (cylinder) bolts on the rotory valve side of the engine.

When installing the rotory valve cover on a Sea Doo 720/717 be sure to use a thread locker such as loc tite on the bottom 2 bolts. From the factory the holes are bored all the way through the cases. The thread locker acts as a sealant to prevent air leaks.

Common Sea Doo and Yamaha standard bore measurements.

4th oversize is 1mm (0.040") larger then standard bore.

Sea doo - 580 is 76mm, 650 is 78mm, 720 and 800 are 82mm and the 951 is 88mm.

Yamaha - 650 is 77mm, 700 and 1100 are 81mm, 760 and 1200 are 84mm.

Sea Doo 2 cycle engine Break-in

non fuel injected

A break-in period is required before operating the engine at full throttle. My recommendation is about 10 operating hours for a fresh engine and 1 hour on a new top end.

During this period, maximum throttle should not exceed 3/4, however, brief acceleration and speed variations contribute to a good break-in. Continued wide open throttle accelerations, prolonged cruising speeds and overloading the engine are detrimental during the break-in period.

To assure additional protection during the initial engine break-in oil (same oil as are using in injection tank) should be added in the fuel tank for the first full fuel tank filling only.

To add injection oil in the fuel tank, proceed as follows:

Fill fuel tank with approximately 5 gallons of gasoline; then, add 2oz of injection oil for every gallon of gas. Fill up fuel tank with gasoline. Do not overfill. In simple terms if your tank holds 11 gallons of gas you would add 22oz of oil to the first tank. This is in addition to the oil injection.

NOTE: It is important to proceed in this order to allow a proper mixing of the oil in the gasoline.

This is while also using the oil injection system as normal.

If you are running premix only on one of our engines we recommend 32:1 fuel oil ratio for break in and 40:1 after the initial engine break in.

Now you can download Sea Doo service manuals for free online. This page isn't ours but it is a free resource.