top speed ?

[mr roach]

i have a 1969 sea ray sv70 16' tri-hull with a smooth hull w no major damage and only a couple of small scrapes which i have filled and sanded flush and smooth,my main power is a 1977 115 mercury I6 that has been rebuilt with approx. 12 hours on it. It sat for a while so the carbs were removed,cleaned re-installed and adjusted. the distributor acted up and i had new bearings and some electrical repaired/replaced and upon re-installed put in a new timing belt and had a link and sync done. The prop is a refurbished one from a very reputable shop and is a 13 1/4 x 17p alum. prop. the engine has power trim that functions correctly and the engine measures out to be correctly installed as far as the position of the cavitation/cv plate in relationship to the hull. At w.o.t. i achieve 5200 rpm but only obtain 25 to 27 mph this is with 2 people and gear and when just my wife and go for a ride i can go between 32 to 36 mph with no gear and i have good hole shot and get on plane quickly in either condition. why am i going these speeds when others from this site with similar set ups report speeds of 45 plus ? i do take on a little water at the end of the day approx 1 to 2 gallons and my foam is not saturated with water. have i overlooked something or is this accurate for my set up ? I was not sure if this was a engine or a prop topic if i posted incorrectly please let me know.

 

[Chinewalker]

Re: top speed ?

If your RPM is correct, it seems a bit low. I'd be aiming for 5800-6000 RPM or so as a max with just you aboard...

 

[carholme]

Re: top speed ?

Models 115 & 1150 115/5000-5500

Gerry

 

[chriscraft254]

Re: top speed ?

You say your foam isn't saturated but you take on a couple gallons of water a day. That really does't make alot of since. Has the boat deck been replaced, if not, that old of a boat probably has saturated foam.

Rpms sound about right. Keep in mind, a trihull that is 16 feet long can be effected speed wise pretty quik when you add people and gear and fuel. Not to many trihulls are speed demons.

Find out how much the original wieght of the boat and motor was, then take the boat and have it weighed, this will tell you if you have water in the foam/hull.

 

[mr 88]

Re: top speed ?

69 hull that is taking on water indicates to me your flotation is waterlogged. How did you check it ? I would go to Sea Rays web and search the archives to see what it is supposed to weigh then take it to a scale house.To the best of my knowledge there is no way to check the flotation for water if you cannot reach it,except for weighing it or ripping up the ENTIRE sub floor.

 

[mr roach]

Re: top speed ?

69 hull that is taking on water indicates to me your flotation is waterlogged. How did you check it ? I would go to Sea Rays web and search the archives to see what it is supposed to weigh then take it to a scale house.To the best of my knowledge there is no way to check the flotation for water if you cannot reach it,except for weighing it or ripping up the ENTIRE sub floor.

thank you for the reply my floor is removable right now as i was in the process of replacing it and have plywood screwed in place when the problem started i checked the foam and it was wet but not saturated it is an odd foam kind of orange in color very dense and seems to be adverse to absorbing water. I also cut a channel in it and added an additional drain so the water goes to my bilge pump and i turn it on several times while i am on the water to check and make sure i am not taking on to much water. Water enters due to two small chips at the transom i believe the previous owner loaded the boat with no protection on the bunks and created the chips. i patched them but upon advice of any body work person used a metal patch in the process and it failed to adhere to the hull and i just have not fixed it. I got approx 2 gallons after 24 plus hours on the water most of the time it is a gallon or less after 8 to 10 hours on the water. I am not trying to have an answer for every problem just have really hit the wall on this issue so if you can think of anything please send it my way and again thank you

 

[mr roach]

Re: top speed ?

thank you for the reply i take on approx 2 gallons after 24 plus hours on the water after 8 to 10 a gallon or less my floor is removable right now and i have checked the foam it is an orange color and very dense and does not appear to absorb water as i cut a channel in and added a drain so it will go to my bilge which i run every so often while on the water just to make sure i am not taking on a lot of water. When i cut the channel it was due to water in the bottom as i had removed the floor to replace it and when i cut the channel there was around 3 inches of standing water and every piece i removed was not saturated and it had the water in for days as i was out of town and could not remove it any sooner. I appreciate the info and i you can think of anything else please let me know. again thank you for the help

 

[Lyle29464]

Re: top speed ?

I would check the tack second. First thing is fix the leak and check to see how far water has intruded in the transom. That must be dried out.

 

[mr roach]

Re: top speed ?

my research indicates the rpm is 5000 to 5500 so i am right there. i appreciate the input if anything else comes to mind please let me know am really out of ideas myself. Happy boating and again thank you

 

[mr roach]

Re: top speed ?

the tach is accurate plus my floor is removable and my floor is split level the water would not previously go to the transom so iinstalled a channel in the foam and an additional drain so it will go to my bilge pump and at that time it had about 3 inches of standing water in it that had been there for at least 2 days and as i cut the channel every piece of foam i removed was not saturated it was wet an if i shook them they would shed the exterior water and had not absorbed any water. the foam is kind of orange and reminds me of the foam that you used to see installed under docks back in the day. i take on approx. 2 gallons of water after 24 plus hours on the water and a gallon or less after 8 to 10 hours on the water i patched the leak but upon advice of a person who does bodywork i used a metal patch in the process and it failed to adhere to the fiberglass and as i am going to replace the floor this spring or summer i have plywood screwed down rite now so i can remove it if need at this time i also have a couple of inspection holes in the floor at this time so i can see down there without removing the floor. If you can think of anything that i may be overlooking please send it my way. Thank you and safe boating

 

[Bondo]

Re: top speed ?

i have a 1969 sea ray sv70 16' tri-hull with a smooth hull w no major damage and only a couple of small scrapes which i have filled and sanded flush and smooth,my main power is a 1977 115 mercury I6 that has been rebuilt with approx. 12 hours on it. It sat for a while so the carbs were removed,cleaned re-installed and adjusted. the distributor acted up and i had new bearings and some electrical repaired/replaced and upon re-installed put in a new timing belt and had a link and sync done. The prop is a refurbished one from a very reputable shop and is a 13 1/4 x 17p alum. prop. the engine has power trim that functions correctly and the engine measures out to be correctly installed as far as the position of the cavitation/cv plate in relationship to the hull. At w.o.t. i achieve 5200 rpm but only obtain 25 to 27 mph this is with 2 people and gear and when just my wife and go for a ride i can go between 32 to 36 mph with no gear and i have good hole shot and get on plane quickly in either condition. why am i going these speeds when others from this site with similar set ups report speeds of 45 plus ? i do take on a little water at the end of the day approx 1 to 2 gallons and my foam is not saturated with water. have i overlooked something or is this accurate for my set up ? I was not sure if this was a engine or a prop topic if i posted incorrectly please let me know.

Ayuh,.... My guess is, yer hull ain't Straight, at the keel line, at the last 4', at the transom...

It probably has a big hook in it, not allowin' proper planing...

 

[mr roach]

Re: top speed ?

thank you bond-o i will look into that,any more advice on where i can find the info needed to be able to properly check it myself or is this something better left to a pro ?. Also i had my carbs cleaned,adjusted and linked and synched but never rebuilt could this be a contributing factor ? . Thank you for your your help and safe boating

 

[wired247]

Re: top speed ?

Try a different prop before you get too excited. A friend loaned me a 19 pitch mercury aluminum prop once and my 60 MPH boat turned into a 40 MPH boat.

 

[Bondo]

Re: top speed ?

thank you bond-o i will look into that,any more advice on where i can find the info needed to be able to properly check it myself or is this something better left to a pro ?. Also i had my carbs cleaned,adjusted and linked and synched but never rebuilt could this be a contributing factor ? . Thank you for your your help and safe boating

Ayuh,.... Find yerself a 4', or better yet a 6' straightedge, 'n hold it against the keel, at the transom, forward...

It should be pretty much Straight,... If ya see air 'tween the straight edge, 'n the hull, that's a Hook, or Hawg....

If the straight edge won't lay flat to the keel, but rocks fore, 'n aft, that's a Rocker, but I doubt yer gonna see that...

Are ya trimmin' the motor up, while underway,..??
If it's trimmed down too far, the hull's gonna Plow, regardless what the keel line looks like...

 

[buzzm19]

Re: top speed ?

76 to 78 115 l6 are the same motor and set up properly are very strong motors, 5000-5400 is max rpms. I usually go by the hole shot and you say it is quick which indicates to me you need more prop and I use only steel props. In your case I would recommend a 13.5/19p stainless prop. When you run the boat wot and trimmed up properly (top of those motors are pretty flat and should be parallel with the water) get someone to look and see that the cavitation plate is about an inch out of the water (the plate your trim tab attaches to) I did mine and had to raise the motor two inches and it really woke up the boat. Also on those motors you need (it is very important) to increase the carb jet size by two (because of the gas today), take out the air bleeder jet and leave it open then put a beebe(beebe gun pellet) and put it in each of the vacuum hoses on all three carbs.(mercury did these two things to lean the motors out at wot because of the gas crunch back then) and these settings are at sea level, higher than sea level needs more adjustment, these motors don't have altitude sensors like cars do today. Everyone here on iboats knows what happens to these motors if you run them lean. I would guess with the proper set up you should be good for the high 40's low 50's with two average weight persons. I would also be careful as those tri huls can be tricky at those speeds and are prone to chine walk. hope this helps Buz

 

[mr roach]

Re: top speed ?

Again bond-o thank you and motor was trimmed up and speed posted the highest speed i was able to obtain. Will straight edge my hull as soon as the rain stops and the ground dries up a bit here in sunny california

 

[mr roach]

Re: top speed ?

buzzm 19 thank you for the reply will double check my motor again but i had someone pilot the boat and i looked over the transom and it looked good but it never hurts to make sure. The 19 prop has been brought up before and half say 17 is the one i want and half say 19 is the one to have my borrow a 19 just to see as my 19 is damaged at the hub and is alum and i think i want to go to s.s. anyway. on the air bleeder the mechanics at the boat shop say do not do it as well as the independent mechanic i used and he used to race merc 115 but again it is 50 50 on that issue but it seems plenty of people have done it for regular performance and not just for racing so what the heck can't hurt to try but i do like the jet suggest you made will look into that and see if it is in the budget lol. Again buzzm19 thank you for your advice happy boating

 

[buzzm19]

Re: top speed ?

MR, I have been into boating for about 40 years and mostly all mercurys. What I suggested to you was what I have done to my 1978 l6 115hp. All of this information was available to me from iboats and when I was looking for the information I would say that I went through probably 600 of the 1300 pages on iboats. To my satisfaction iboats to me is like winning the lottery. If you sit down and start surfing iboats forums you will find all the answers there and more. I only regret all of the reading and manuals I have used in the past and if iboats were there then it would of been a lot easier. Buz

 

[mr 88]

Re: top speed ?

I have a rebuilt 78 1500 and tried going up one size on the jets,it ran better with the stock jet. Generally they are fat from the factory as they do not want a lot of leaned out motors blowing up.As far as the gas goes most people retard the timing by a couple degrees to take care of that,not increase the jet size by two. I would set up the carb per manual,no BBs no vacuum hose pinched off,engineers designed them that way for a reason..I also believe after looking at your numbers that a 19" prop will be too much and you are just going to lug her.High 40's low 50's for speed is not going to happen with that hull, more like 40 max.I run mid 50's on a 15' 450 lb twin tunnel and the engine is fresh with hi domes/balanced crank/rods etc weighed and a 20" SS wheel and jacked up a inch and a half off the transom. According to Sea Ray your hull comes in at 1200 lbs,dry weight.

76 to 78 115 l6 are the same motor and set up properly are very strong motors, 5000-5400 is max rpms. I usually go by the hole shot and you say it is quick which indicates to me you need more prop and I use only steel props. In your case I would recommend a 13.5/19p stainless prop. When you run the boat wot and trimmed up properly (top of those motors are pretty flat and should be parallel with the water) get someone to look and see that the cavitation plate is about an inch out of the water (the plate your trim tab attaches to) I did mine and had to raise the motor two inches and it really woke up the boat. Also on those motors you need (it is very important) to increase the carb jet size by two (because of the gas today), take out the air bleeder jet and leave it open then put a beebe(beebe gun pellet) and put it in each of the vacuum hoses on all three carbs.(mercury did these two things to lean the motors out at wot because of the gas crunch back then) and these settings are at sea level, higher than sea level needs more adjustment, these motors don't have altitude sensors like cars do today. Everyone here on iboats knows what happens to these motors if you run them lean. I would guess with the proper set up you should be good for the high 40's low 50's with two average weight persons. I would also be careful as those tri huls can be tricky at those speeds and are prone to chine walk. hope this helps Buz

 

[buzzm19]

Re: top speed ?

MR, I have to retract my statement, I didn't read your post close enough and did not realize the weight of your sea ray and sea ray's are heavy boats. mr88 is closer to what your application is than me on the heaver boat you have. To mr88 I had a 1971 14' glastron slotted hul with a similar built motor like yours and you think you have a rocket ship? Buz