Low RPM/No Spped

[olds72]

My boat is a 90 250 DA with a 5.7 Merc. Running a 15.25 x 15 prop. Was out this weekend on a smooth Lake Erie with 4 adluts on board. I had trouble getting on plane and could only reach speed of 18 - 19 MPH at 3400 RPM WOT. based on the prop specs I should beable to get 4600 RPM at WOT. I have not had a chance to get my boat on the hoist to look at the prop. Lets say it checks out. What else should I be looking for? Engine was running good. I did not notice any strange sounds or have any fluxuation in RPM.

 

[dvx216]

bottom needs cleaned?

 

[olds72]

bottom needs cleaned?

You mean bottom of boat, not bottom end of out drive. That alge could slow my boat down that much?

 

[northshore]

Have you been in the water all summer and do you guys have zebra mussel issues up there?
What is your normal top speed?

 

[paulswagelock]

You mean bottom of boat, not bottom end of out drive. That alge could slow my boat down that much?

Yes.

 

[CliffA]

You mean bottom of boat, not bottom end of out drive. That alge could slow my boat down that much?

yes...I am experiencing the same thing right now with my boat....it is amazing how much performance can be affected by a fouled hull bottom and running gear....

cliff

 

[olds72]

Have you been in the water all summer and do you guys have zebra mussel issues up there?
What is your normal top speed?

i have had both my boats in since May. My S24 runs great and normal. Top speed at WOT 32-35

 

[northshore]

If the bottom paint on both is not the same, I'd have the boat lifted just to make sure its clean.
at least that will get bottom condition verified.

I've seen growth and zebra mussels kill boat performance in our area of Lake Erie.

 

[Quint4]

I hauled my boat for bottom cleaning and painting early this season. Picked up 11 mph and 600 RPM.

 

[olds72]

I'm going to get my boat on the hoist Saturday and power wash the bottom. I'm going to swap out my prop. Then hit the lake for a test.

 

[northshore]

I'm going to get my boat on the hoist Saturday and power wash the bottom. I'm going to swap out my prop. Then hit the lake for a test.

It might just be the test engineer side of me but, is there a reason besides the reduced speed issue that you are changing out the prop?
Change two things at once and your problem goes away, you cant be certain what fixed it... (my 2 cents - might actually be worth less than that)

 

[olds72]

It might just be the test engineer side of me but, is there a reason besides the reduced speed issue that you are changing out the prop?
Change two things at once and your problem goes away, you cant be certain what fixed it... (my 2 cents - might actually be worth less than that)

I figure if I'm going to pull it out of the water to wash the bottom, I'm going to put my spare prop on. We are charged to use the hoist and the hoist my be busy on Saturday. People are starting to pull their boats out for the season.

 

[olds72]

Re: Low RPM/No Speed

My bottom wasn't to bad. Guys at the club didn't think it was dirty enough to slow me down that much. I swapped the prop. The specs call for a 15.25 x 15 it had a 16 x 16 on it. The dealer said they put those larger props on to accomadate more people. They said the 16 inch prop wouldn't cause me to loose the much RPM. He said on about 500 RPM. I haven't gone for a ride yet since I changed the prop. Probably tomorrow. Honey DO list is to long today.

 

[olds72]

After changing the prop and cleaning the bootom a couple of weeks ago, I finally had the chance to take my boat out for a ride. My RPM's were better at 4000 @WOT, but the speed was the same with only 2 of us on the boat. I put the stock prop back on 15.25 x 15. I'm going to do a complete tune up on saturday. Cap & rotor, wires, plugs, fuel filter and water separator. One thing I need to check is the throttle cable travel. Making sure my secondaries are opening completely. If this don't work I'm not sure where to go next. The season is so short and boats are coming out of the water.

 

[Sprint7TW]

Check your timing also when you do the ignition parts.

 

[olds72]

my buddy seems to think that when i did the belows, I didn't get the linkage adjusted correctly. Thoughts

 

[olds72]

Just an update on my issue. a couple of weeks ago i did a complete tune up. Plugs, wires, cap & rotor, fuel flilter and fuel water separator. My RPM is now 4400 @ WOT my speed is 22.5 on my GPS. This is an improvement.