lost max rpm on 250hp scarab

[wango tango]

If everyone is in agreement that there is something else wrong here and not the warm conditions, I will bring it back to dealer. The dealer tech here says it's ok to lose that rpm that's the problem

 

[wango tango]

Best spark plug gap for performance, I believe the spec is from 28-31

 

[Scarabpaul]

I think you need to take it back to the dealer and get a second opinion...... if they have another 250hp 19FTer on the lot tell him to take you out in that one to compare..... I was out last weekend in 30+ deg C. weather and no loss in RPM.

 

[wango tango]

Thanks for the feedback,
What was your max RPM running at?

 

[Scarabpaul]

8100. I would do as others suggested and get new plugs. for your own peace of mind..... dealer may have checked them and not replaced them. if its not the plugs then you have a spare set which is always good to have. otherwise, I would bring it back to the dealer.

 

[wango tango]

Well put new plugs in and top off gas tank and nothing changed!(premium)
Now this morning the outside temperature was 75f and water temp dropped to 77f, got 7840rpms out of it.
Picked up wifee at dock and took it out again and could not get more than 7700.
Put octane booster in and actually lost 50 rpm?. Pulled plugs yellow gunk on them from octane booster.
Going to bring in Tuesday to dealer, sucky part is tempature going down to the 70s so it may not show loss of rpm for dealer.

 

[R502]

Best spark plug gap for performance, I believe the spec is from 28-31

I replaced the plugs before winter storage last year. The spec show .30 gap. The ones I pulled were original from the factory. They were gapped at .025, same exact plugs as I replaced them with. I gapped the new ones at .030.

 

[wango tango]

Back at dealer,
Both brp and scarab is now involved with it.
I did everything I can do, so I hope that someone can figure it out soon, we love the boat.
Thanks for all the help guy's

 

[WaltB]

The highest RPM I have seen on my boat on either 250HP is 7,600 RPM. Does not matter if I go max throttle early on or later in the day. The engines are consistent at a max of 7,600 RPM.

 

[wango tango]

Update!!!!!
Dealer did nothing and had nothing.
So I found a guy that once built race boats and he looked at my boat.
First thing he noticed is that the intake hoses are laying/ touching the exhaust/pipes!!!! Had me Insulated the hoses. Add 2 more vents next to existing ones for more air flow to engine and exhaust heat. I now continuously get 7900rpm, 40+mpr, engine compartment temp down from 105-110 to 80-90f.
One thing I found was that humidity also effects RPM!! Humidity below 50%I get 7900/8000 all day long ,60% and higher I dropped down to about 7800 so it's just not water temp or air temp, humidity seems to play a big part in these superchargers.

 

[WaltB]

Can you post some pictures of the new vents you installed. Cooling the engine bay is good for lots of reasons.

Thanks,

Walt

 

[R502]

Update!!!!!
Dealer did nothing and had nothing.
So I found a guy that once built race boats and he looked at my boat.
First thing he noticed is that the intake hoses are laying/ touching the exhaust/pipes!!!! Had me Insulated the hoses. Add 2 more vents next to existing ones for more air flow to engine and exhaust heat. I now continuously get 7900rpm, 40+mpr, engine compartment temp down from 105-110 to 80-90f.
One thing I found was that humidity also effects RPM!! Humidity below 50%I get 7900/8000 all day long ,60% and higher I dropped down to about 7800 so it's just not water temp or air temp, humidity seems to play a big part in these superchargers.

Would love to see how the hose insulation turned out as well. Good find.

 

[wango tango]

Pics of mods you can see the new vents added far left and right. Move the exhaust to far left, added intake fan to far right.

 

[Eddie Zepeda]

good morning everyone,
got back my scarab 195 yesterday from dealer for the 25 hr service check and oil change , took it to the water and now i don't get max rpm(8100/45mpr), only 7800/ 40 mpr
oil is reading alittle high above top mark? nothing in impeller

Any feedback would be great

I' having same trouble. My 215 won't go over 40mph and 7k rpm.
Dealer said "hmm we'll take a look at it"

 

[wango tango]

That's a lot more rpms lost than I had.