Prop or Engine Problem

[JGra]

I have a new to me 1996 Sundird Spirit 170 with a 1996 Evinrude 88 SPL. The boat runs well on the water but I can only at its best got 4100 RPM's and 34 MPH (dash Speedo) out of it. I am fine with the speed and am only concerned about the engine operating at the correct RPM. I do not know what prop is on it. I have removed it and connot find any numbers on it at all. It has looked like it has had some rework done to it. The boat is 17 ft long and weight (according to the net) 1900-2000 lbs dry. I looked at the engine today and pulled the plugs. They looked VERY VERY worn, so much that the gap on all 4 plugs were gapped at about 70 thousands. I replaced the plugs and will try that and see if there is any improvement. I am going to borrow a compression gauge to see where its at but it purs like a kittin in the water. I did pull 1 plug at a time while it was running on the muffs at about 1500 rps and you can tell it is firing on all 4. The boat has a brand new tach and the engine has a brand new recifier. Which way should I go first. The prop is chewed up a bit and I want to replace it at one point but dont know where to start.

 

[jc turtle]

Re: Prop or Engine Problem

Hi, my son has the same boat, but it is a 1989,boat and 88 motor. The prop that he has is a 13.25 x 15.
Check out your prop to see what it is, so you can get the best out of the boat. You never can tell what
the previous owner put on it to sell it.,. Check it out and let us know. John

 

[metriccrescentwrench]

Re: Prop or Engine Problem

Those worn out plugs certainly weren't doing you any favors. Did they all look about the same?

Yes, check the compression to make sure you don't have any serious problems, then after that it certainly sounds like a different prop may help. How well does the boat get on plane now? Will it jump right up or does it wallow along and sooner or later decide to plane? Just as kind of a wild a#% guess I'm thinking a prop with about a 15 inch pitch. What would be great for you is if you could borrow a couple of props to try. edit to add: I see that whilst I was typing my guess was confirmed.

Oh, find a gps (even one on a phone) to check your speed. Never trust a speedometer on a boat, they lie.

 

[JGra]

Re: Prop or Engine Problem

Yes all the plugs looked exactly the same. The boat get on plane kinda ok. With me and the wife it does ok I think. Last time out with 4 of us in the boat it struggled to get up but did get there. It does not ever just jump up there. The prop on there now is a 13x something. No markings on it at all. It had been reworked at one point. I have been trying to find out what came with the boat as the boat and motor are as is when bought new. I have not had any luck finding that info yet though.