Prop engine question Shabah 198 4.3
 

I have a 1997 Mariah Shabah 198 with a 205hp 4.3l v6 and a 1.62/1 outdrive gearing sporting a 14.5" x 19p stainless Mercury marine stainless prop. I bougt this boat last fall and dont have previous experience to go by so I'm asking you. WOT is 4600 at 46mph (Gps) all trimmed out with a half tank of gas and just me in the boat 1500ft altitude, does that sound right or do you think it should have more? The performance is fine for me but after reading many posts on line I am wondering if it should be able to pull more prop. Thanks in advance

Re: Prop engine question Shabah 198 4.3
 

4600rpm at WOT seems just a tad low for a 19" prop and the 46mph also just a tad low as you should be closer to 47-48 with that prop. Trouble is if you increase your pitch to gain a couple of mph you lose rpms and with your recommended rpm range of 4400 - 4800 for that engine that could push you below the range. There are alternatives though. You could try a 20" - 4 blade prop. That might only lose 100 rpm but may also gain you 1-2mph with some nice mid-range punch. If you are flush with a little spare cash, you could also consider a 21" High 5 prop which should give you a 2mph gain without the rpm loss and still give a reasonable holeshot.

Re: Prop engine question Shabah 198 4.3
 

thanks for the reply MikeyT, I have a new 19p Solas Rubex 4 blade that I tried and was only able to get 4100 and 40 mph so I went back to the SS 3 blade prop. I wasnt expecting such a rpm loss from that extra blade, the engine runs nice and smooth with 40 p of oil pressure, but maybe I need to do a compression check to see if its getting a little tired I would like to try a High 5 but they are a little pricier than my checkbook can provide so I was thinking possibly a 17 Solas 4 blade prop. Will have to get that compression checked first tho

Re: Prop engine question Shabah 198 4.3
 

Just wanted to update on what I had found, I changed to a 17p 14 1/2 4 blade Solas Rubex Prop and now am running at 4800rpm and around 40mph, which is a little slower top end but seems to cruze and planes fairly quick so I think this will be the one we use for water sports from now on. Next season we may try smart tabs for quicker planing

Re: Prop engine question Shabah 198 4.3
 

Sounds like you have a tired engine. That 17" prop should have you jumping out of the hole with the 4.3 and your WOT's should be higher than 4800.

Re: Prop engine question Shabah 198 4.3
 

Ya sadly I think you are right, I have'nt gotton a compression test done yet. I thought we could run it through this season and have it rebuilt over the winter. I will check the compression and post my results.

Re: Prop engine question Shabah 198 4.3
 

Well you were right!! I took a compression check and 2 cylinders were down, so the engine came out and when we dug into it a broken piston on one cylinder and a scored piston on another. Thanks

Re: Prop engine question Shabah 198 4.3
 

Sorry to hear that but.... your boat will be like new when its done!

Re: Prop engine question Shabah 198 4.3
 

Ya Thats what I figure too, and I'm excited to see what it will perform like with a fresh engine, so Its not so bad.