Dumb Question Merc 1150

[cmikee]

I have a 1970 Merc 1150. I have a prop with a 21 Pitch. When I try to get high RPM's I can't. The motor seems to top out at 4K RPM's. I believe that these motors can get more RPM's than that. I just put this 21 Pitch prop on there thinking it will go faster than the 19 pitch I had. My Dumb Question is, Does the higher pitch normally give higher speeds? And How come my motor is only hitting 4K? I am burning regular unleaded with 50:1 mixture. Thanks for any input!

[wrechin2]

higher pitch props will yield higher speeds if you can turn it. (most cases) For every inch of pitch you go up it will usually drop rpm by 200-300 rpm. that engines power range is 4800-5600 rpm at wot. If you were only turning it 4800 to begin with now you are over proped. Design of prop also is a factor. I have a 19 and a 21 stainless for my 73 150hp. I really don't see but about 2 mph difference between them. But the 19 really shoots out of the hole! Hope this helps.

[gaineso]

How is the boat set up? Motor all the way down or up a little? Definitely go back to the 19" prop. May even need to go to a 17" with that combo.

Have you checked compression? That engine should push that boat better than that. May just be overpropped though.

You might consider going to 40:1 oil mix and premium gas on that engine. Seems to be the consensus from the inline gurus here. (Not including me in Guru status. I'm learning too.)

Definitely need that motor propped to turn up around 5500 RPM. That will give you max speed and engine life.

[CrayzKirk]

Hi,

I would check the timing (21* max, ignore sticker), run midgrade/premium gas and oil. Follow the rest of the advice. Search the forums for information on converting your 1150 to a 1350 by changing the carb venturi, jets and openning up the reed stops. Your motor uses the high dome pistons and will be prone to detonation if you run it at that low rpm. It is called lugging the motor and an inline likes to wind up over 5000 rpm.

My $0.03 worth (inflation, ya know!)

Kirk

P.S. I'm not a guru either. More like a parrot with an ok memory. Just repeating what I remember the really smart people have to say!!!

[Raceman]

You'll hurt that motor with it pitched with that much load if that's no the problem with it already. Using the later reed stops is the biggest single component in the 135 conversion and will make several MPH difference, but you've got to pull the powerhead and get the front off the block and pull the crank up enough to get to the reed blocks, so it's not a simple job or one for someone not somewhat experienced with inlines. I don't run anything less than 32:1 and super unleaded in any of mine. Gaineso's advice on compression check is the first place to start.

[sho305]

My '73 150 on a hefty 17' vee Checkmate BR will run around 5700 depending on the day with a 20p Laser SS. It has hit 6,000 but may have been slipping. Runs same rpm to mph with 21 aluminum Merc prop, but can't trim it enough for top speed as motor is raised and aluminum prop blows out by then at maybe 5400. The Laser never does.

You have to prop it to make rpms right, or change the hull/weight to make it faster. Due to design and slippage, the same pitch may not be the same rpm from one prop to another prop. The inline is not so good out of the hole with a tall prop either, many have the next size smaller pitch for skiing where you might be able to get away without that on another motor. Yours must be a dog now to get on plane; it will be much better when propped at the right rpm. Mine takes a few seconds to plane if I hammer it.

Make sure you get it running good first before you waiste time trying a bunch of props. It sure sounds nice at 5500-6000 rpm though:cool:

[gaineso]

sho305, I used to have a 19" aluminum with vent holes for skiing. It would easily pull 2 200 lb guys up on slaloms. had to run it about an inch lower. Would pull 5800 at 48MPH. Turbo 22 at 3 1/2" below pad runs at 6000 and 59.4 GPS Too hot now to make any speed runs and try and get above 60.

Yeah, props are a major setup point. But, need to be sure what else may or may not be wrong with the motor and rigging.

[sho305]

Oops, and when it runs good get it at the right rpm for your 1150 +any mods, not my 1500 that likes close to 6,000rpm. Make sure the carbs are opening all the way if someone has not mentioned that.

I am sure I could pull one skier up fast but never have. Yours runs good gaineso.:) I'll pad my Checkmate vee if I can ever get to it...but then I might have to go V6...we will see. Not sure I could ever see 60 with my 930lb hull & inline even with pad and setback. At least I got my bayliner from 42 up to 47 on the speedo in the last 1/2 year;) , all with simple S&F mods and a Force motor too...:eek:

[cmikee]

Thanks Guys for all of the help. I will check all of the things here and post my results here also.

[sho305]

Speaking of trying props on the inline; I got an OMC prop that had a bigger diffuser on it and could not get over 4500rpm. Could not figure out what was going on...was way rich on top...never heard of that before but it happened. Doh!

Let us know how it goes.

[cmikee]

Ok I changed the Prop to a 19 pitch prop. I Did not check compression Yet. I Took the boat out and it seemed to do alot better taking off. I tried to top out and only hit 4K RPM's this time I hit 35 MPH. Well I kept trying different Engine Depths and they were not different still 4K. So I decieded to go back to the dock. I tried to drive the boat on the Trailor and it wouldn't do it. It would bog down every time I would try and push the boat on the trailor. I Know I need to check the compression but I wanted to update you Guys on what was happening. Thanks again for all the input! Oh yea I did Put 93 octane Gas and 40:1 mixture in the gas.

[sho305]

There is something wrong with the tune of that motor or you have it on a 24' hull. 19p should work unless you have a big heavy boat. Does it run steady, no surging/etc? Did you check the color of the plugs after wot? What hull do you have?

[cmikee]

I did not check the plugs after WOT. The motor runs good after about 2K under 2K it skips a little and cuts off if going from Idle to Gear. But it has always done this. I have a 16Ft Glasstron Tri Hull. It's suprisingly heavy for a 16Ft I guess it's all the Fiberglass. I do believe I have retained water in the front part of the boat and it won't come out of the drain plug for some reason. I am going to make myself a list from these posts for the next time I go. (boat is in storage near lake)

[sho305]

You need to make sure the carbs are clean on these motors. That, new plugs, and good fuel flow cures a lot of problems. You may have to set the idle mixture. I set mine trolling in the lake with someone steering while I closed all the idle jets until it sputters, then back them out until smooth. Then I back them out another 1/4 so it is a hair rich and kills less. Sometimes it will load up after idleing in gear about 15 minutes. It is about 800 in gear idle now. Only wants to kill on a shift when cold. I did them over and over one by one and they are within 1/2 turn of each other now. Much better. That was after the carb cleaning, new line, tank flush, set timing, etc. On another boat I set the mixture perfect(rich enough to idle smooth) at about 68 degrees outside trolling, that will make it a little rich when it is warmer out.

My 17' Checkmate BR is not light. I did find water in the seat pedestles; must have flooded once and I could hear it while rocking the trailer. I drilled a hole in the bottom corner to drain them. Many hulls have waterlogged foam in them you have to dig out too. My '73 is to old for foam. I think my cav plate is about 1-2" above the bottom, the motor is raised 2" on the 20" transom. I have to trim the $@% out of it to go fast. Any extra weight in the bow will kill speed. I loose 4mph with a passenger. I have to run the Laser 20p to get lots of bow lift or the prop blows out and I loose 6mph @ lower trim. Needs a jack bad. Trying to get it in for a transom this winter if I can find time. Not many half fast/sporty BRs to find here. Not in my current budget anyway. Waterlogging will kill your speed.

Glasstrons have a good rep around here. They are not the fastest, but do ok and hold up well much like the Checkmate. I am sure it will do better than that. My 85hp Force(Chryco) on the '83 16' Bayliner BR is hitting 47 on the speedo with a new pickup, so maybe 40+mph real speed. Yours should do that no problem. Get it running good so you can enjoy it. Take any weight out you can, make sure bottom is clean and straight. Have fun.:cool: I had a 16' glass boat with a 80hp Merc 1974 I4 that ran 38 on the speedo and the same mph read next to another boat. This is the best speed freak OB site I found, but any running boat is faster than a dock.;) Even my poor Bayliner/Force I have to run for now. It is good for laughs though.:D It has a 2:1 gear and 19p I found now w/unknown rpms until next weekend when I test it...and see if the wet sanded pad and LU make it faster:p

[CAP'N ROG]

i have identical problem its posted under inline problem.post your compression readings mine were 1-5 110 6 100 good luck

[Jeff_G]

Sho, I have to meet you one day. Anyone with the balls to post not just one but two pics of a bayliner and Force motor here must be somethin'!!!!! :D :D :D

[sho305]

Ahh, uh, errr....I shrank it, but the pic came out bigger than I thought.:eek: I get lots of laughs out of the Force/Bayliner, the $200 boat with about $300 in materials and $2,000+ in my cheap labor.:) I'll be damned if I was going to sit on the dock while I fixed one of my other boats or bought something else, and I kinda wanted to do a transom on something I didn't care about first. I can pull it out of the lake with my golf cart too, a sure plus for easy use. Didn't mean to offend anyone, and I would be happy to pull anybody into shore with it...as long as it keeps running :D

My 1500 has 120-122psi; throttle open, plugs out, on starter, about 15 min after it was run.

My cart is great fun and even works in the yard sometimes hauling stuff, and boats. See, you don't have to go 100mph to have fun...but 100mph might be more fun:D Have a pic of it pulling the bayliner I have to scan in yet. Sure freaks people out at the lake, and last time I pulled it out a Grand Cherokee had to use 4wd to pull a pwc out after me...heh heh heh:cool:

[Bill Gohr]

Doesn't the 70 1150 have 1:78's in it? If so his 21 is a 23, also look up in the exhaust passage in the gearcase and see if the tuner plate didn't fall out as they did all the time, it will lay in there and block off the exhaust, makes motor a pig

[crazy horse]

Bill, I don't know where RM is but you are right about the gear ratio. The 1970 115 and 135 had 1:78 gears, Also that's the only inline gear sets that were made in left and right hand I think:confused:

[sho305]

Plugged exhaust? That would be bad:eek:

If you can still take a joke, I did run 4950rpm@42mph(speedo) w/a passenger holding the digital tach yesterday on the little force:D At 10% slip and 2:1 with a 19p that is 40.1 on a calculator. I did run 44-45 on the speedo with just me, could not get 47 due to hot weather.

I think I need to run my inline Merc on a hose just to hear it.:(