90hp Merc 3cyl reaches 3000RPM but takes awhile to go over 3000RPM

[casualfisher]

So I have a 95 90hp Merc 2 stroke. Not under load it revs no problem but under a load speed and RPM's quickly pick up to 3000 RPM no problem. But it takes 2 min or more to go above 3000 RPM, and will peak at about 4300 RPM. It should peak at 5500 RPM.

Compression good 120 +-1 on all 3 cylinders cold with carbs open.

No fuel issues, fuel tank breather good, fuel pump rebuilt, all fuel lines and primer bulb replaced and carbs rebuilt. This was done due to a rotten primer bulb had black rubber in fuel filter which tore inside allowing it to get into my carbs. Clear line between filter and carbs shows no air bubbles and is always full

I'm thinking stator is bad on the high side and it's taking a bit to build power but still won't build enough to take it to full RPM. Or could it be the switchbox. The regulator and the switchbox and coils are new. Thoughts?

 

[Chris1956]

Gee, what prop pitch and what kind of boat? For extra credit, what is the gear ratio of your gearcase? Have you changed props recently?

Revving up under no load is not relevant. You could ohm out the high speed stator windings.

 

[casualfisher]

13.25X17 pitch prop have not changed prop and it’s not spun. 16’ smokercraft pro mag. Gear ratio 2.31:1 trying to find out what the ohm reading on the windings should be and where to put the leads to test. I’m pretty handy with things but no expert on boat motors.

 

[Faztbullet]

Check spark

 

[cyclops222]

Changed to new sparkplugs ?

 

[casualfisher]

Check spark

By the timing light I do have spark just not sure how strong it is under high speed load

 

[casualfisher]

Changed to new sparkplugs ?

Plugs and coils are new

 

[casualfisher]

Gee, what prop pitch and what kind of boat? For extra credit, what is the gear ratio of your gearcase? Have you changed props recently?

Revving up under no load is not relevant. You could ohm out the high speed stator windings.

13.25X17 pitch prop have not changed prop and it’s not spun. 16’ smokercraft pro mag. Gear ratio 2.31:1 trying to find out what the ohm reading on the windings should be and where to put the leads to test. I’m pretty handy with things but no expert on boat motors.

 

[Texasmark]

13.25X17 pitch prop have not changed prop and it’s not spun. 16’ smokercraft pro mag. Gear ratio 2.31:1 trying to find out what the ohm reading on the windings should be and where to put the leads to test. I’m pretty handy with things but no expert on boat motors.

Having had a 17 1/2 FT aluminum Fish Master Bass Boat with a stock Merc 90 with the 2.33 ratio and a Ballistic, 13+" by 24P Ballistic 3 blade prop. you have a picture of the performance in my Avatar kissing 50 MPH at 5700-6000 RPM, about 800' of altitude on a cool spring morning.

Unless you have severe engine or boat problems your 17P prop should smoke your RPMS.........